--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/util/Collections.java Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,3876 @@
+/*
+ * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package java.util;
+import java.io.Serializable;
+import java.io.ObjectOutputStream;
+import java.io.IOException;
+import java.lang.reflect.Array;
+
+/**
+ * This class consists exclusively of static methods that operate on or return
+ * collections. It contains polymorphic algorithms that operate on
+ * collections, "wrappers", which return a new collection backed by a
+ * specified collection, and a few other odds and ends.
+ *
+ * <p>The methods of this class all throw a <tt>NullPointerException</tt>
+ * if the collections or class objects provided to them are null.
+ *
+ * <p>The documentation for the polymorphic algorithms contained in this class
+ * generally includes a brief description of the <i>implementation</i>. Such
+ * descriptions should be regarded as <i>implementation notes</i>, rather than
+ * parts of the <i>specification</i>. Implementors should feel free to
+ * substitute other algorithms, so long as the specification itself is adhered
+ * to. (For example, the algorithm used by <tt>sort</tt> does not have to be
+ * a mergesort, but it does have to be <i>stable</i>.)
+ *
+ * <p>The "destructive" algorithms contained in this class, that is, the
+ * algorithms that modify the collection on which they operate, are specified
+ * to throw <tt>UnsupportedOperationException</tt> if the collection does not
+ * support the appropriate mutation primitive(s), such as the <tt>set</tt>
+ * method. These algorithms may, but are not required to, throw this
+ * exception if an invocation would have no effect on the collection. For
+ * example, invoking the <tt>sort</tt> method on an unmodifiable list that is
+ * already sorted may or may not throw <tt>UnsupportedOperationException</tt>.
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/../technotes/guides/collections/index.html">
+ * Java Collections Framework</a>.
+ *
+ * @author Josh Bloch
+ * @author Neal Gafter
+ * @see Collection
+ * @see Set
+ * @see List
+ * @see Map
+ * @since 1.2
+ */
+
+public class Collections {
+ // Suppresses default constructor, ensuring non-instantiability.
+ private Collections() {
+ }
+
+ // Algorithms
+
+ /*
+ * Tuning parameters for algorithms - Many of the List algorithms have
+ * two implementations, one of which is appropriate for RandomAccess
+ * lists, the other for "sequential." Often, the random access variant
+ * yields better performance on small sequential access lists. The
+ * tuning parameters below determine the cutoff point for what constitutes
+ * a "small" sequential access list for each algorithm. The values below
+ * were empirically determined to work well for LinkedList. Hopefully
+ * they should be reasonable for other sequential access List
+ * implementations. Those doing performance work on this code would
+ * do well to validate the values of these parameters from time to time.
+ * (The first word of each tuning parameter name is the algorithm to which
+ * it applies.)
+ */
+ private static final int BINARYSEARCH_THRESHOLD = 5000;
+ private static final int REVERSE_THRESHOLD = 18;
+ private static final int SHUFFLE_THRESHOLD = 5;
+ private static final int FILL_THRESHOLD = 25;
+ private static final int ROTATE_THRESHOLD = 100;
+ private static final int COPY_THRESHOLD = 10;
+ private static final int REPLACEALL_THRESHOLD = 11;
+ private static final int INDEXOFSUBLIST_THRESHOLD = 35;
+
+ /**
+ * Sorts the specified list into ascending order, according to the
+ * <i>natural ordering</i> of its elements. All elements in the list must
+ * implement the <tt>Comparable</tt> interface. Furthermore, all elements
+ * in the list must be <i>mutually comparable</i> (that is,
+ * <tt>e1.compareTo(e2)</tt> must not throw a <tt>ClassCastException</tt>
+ * for any elements <tt>e1</tt> and <tt>e2</tt> in the list).<p>
+ *
+ * This sort is guaranteed to be <i>stable</i>: equal elements will
+ * not be reordered as a result of the sort.<p>
+ *
+ * The specified list must be modifiable, but need not be resizable.<p>
+ *
+ * The sorting algorithm is a modified mergesort (in which the merge is
+ * omitted if the highest element in the low sublist is less than the
+ * lowest element in the high sublist). This algorithm offers guaranteed
+ * n log(n) performance.
+ *
+ * This implementation dumps the specified list into an array, sorts
+ * the array, and iterates over the list resetting each element
+ * from the corresponding position in the array. This avoids the
+ * n<sup>2</sup> log(n) performance that would result from attempting
+ * to sort a linked list in place.
+ *
+ * @param list the list to be sorted.
+ * @throws ClassCastException if the list contains elements that are not
+ * <i>mutually comparable</i> (for example, strings and integers).
+ * @throws UnsupportedOperationException if the specified list's
+ * list-iterator does not support the <tt>set</tt> operation.
+ * @see Comparable
+ */
+ public static <T extends Comparable<? super T>> void sort(List<T> list) {
+ Object[] a = list.toArray();
+ Arrays.sort(a);
+ ListIterator<T> i = list.listIterator();
+ for (int j=0; j<a.length; j++) {
+ i.next();
+ i.set((T)a[j]);
+ }
+ }
+
+ /**
+ * Sorts the specified list according to the order induced by the
+ * specified comparator. All elements in the list must be <i>mutually
+ * comparable</i> using the specified comparator (that is,
+ * <tt>c.compare(e1, e2)</tt> must not throw a <tt>ClassCastException</tt>
+ * for any elements <tt>e1</tt> and <tt>e2</tt> in the list).<p>
+ *
+ * This sort is guaranteed to be <i>stable</i>: equal elements will
+ * not be reordered as a result of the sort.<p>
+ *
+ * The sorting algorithm is a modified mergesort (in which the merge is
+ * omitted if the highest element in the low sublist is less than the
+ * lowest element in the high sublist). This algorithm offers guaranteed
+ * n log(n) performance.
+ *
+ * The specified list must be modifiable, but need not be resizable.
+ * This implementation dumps the specified list into an array, sorts
+ * the array, and iterates over the list resetting each element
+ * from the corresponding position in the array. This avoids the
+ * n<sup>2</sup> log(n) performance that would result from attempting
+ * to sort a linked list in place.
+ *
+ * @param list the list to be sorted.
+ * @param c the comparator to determine the order of the list. A
+ * <tt>null</tt> value indicates that the elements' <i>natural
+ * ordering</i> should be used.
+ * @throws ClassCastException if the list contains elements that are not
+ * <i>mutually comparable</i> using the specified comparator.
+ * @throws UnsupportedOperationException if the specified list's
+ * list-iterator does not support the <tt>set</tt> operation.
+ * @see Comparator
+ */
+ public static <T> void sort(List<T> list, Comparator<? super T> c) {
+ Object[] a = list.toArray();
+ Arrays.sort(a, (Comparator)c);
+ ListIterator i = list.listIterator();
+ for (int j=0; j<a.length; j++) {
+ i.next();
+ i.set(a[j]);
+ }
+ }
+
+
+ /**
+ * Searches the specified list for the specified object using the binary
+ * search algorithm. The list must be sorted into ascending order
+ * according to the {@linkplain Comparable natural ordering} of its
+ * elements (as by the {@link #sort(List)} method) prior to making this
+ * call. If it is not sorted, the results are undefined. If the list
+ * contains multiple elements equal to the specified object, there is no
+ * guarantee which one will be found.
+ *
+ * <p>This method runs in log(n) time for a "random access" list (which
+ * provides near-constant-time positional access). If the specified list
+ * does not implement the {@link RandomAccess} interface and is large,
+ * this method will do an iterator-based binary search that performs
+ * O(n) link traversals and O(log n) element comparisons.
+ *
+ * @param list the list to be searched.
+ * @param key the key to be searched for.
+ * @return the index of the search key, if it is contained in the list;
+ * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The
+ * <i>insertion point</i> is defined as the point at which the
+ * key would be inserted into the list: the index of the first
+ * element greater than the key, or <tt>list.size()</tt> if all
+ * elements in the list are less than the specified key. Note
+ * that this guarantees that the return value will be >= 0 if
+ * and only if the key is found.
+ * @throws ClassCastException if the list contains elements that are not
+ * <i>mutually comparable</i> (for example, strings and
+ * integers), or the search key is not mutually comparable
+ * with the elements of the list.
+ */
+ public static <T>
+ int binarySearch(List<? extends Comparable<? super T>> list, T key) {
+ if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
+ return Collections.indexedBinarySearch(list, key);
+ else
+ return Collections.iteratorBinarySearch(list, key);
+ }
+
+ private static <T>
+ int indexedBinarySearch(List<? extends Comparable<? super T>> list, T key)
+ {
+ int low = 0;
+ int high = list.size()-1;
+
+ while (low <= high) {
+ int mid = (low + high) >>> 1;
+ Comparable<? super T> midVal = list.get(mid);
+ int cmp = midVal.compareTo(key);
+
+ if (cmp < 0)
+ low = mid + 1;
+ else if (cmp > 0)
+ high = mid - 1;
+ else
+ return mid; // key found
+ }
+ return -(low + 1); // key not found
+ }
+
+ private static <T>
+ int iteratorBinarySearch(List<? extends Comparable<? super T>> list, T key)
+ {
+ int low = 0;
+ int high = list.size()-1;
+ ListIterator<? extends Comparable<? super T>> i = list.listIterator();
+
+ while (low <= high) {
+ int mid = (low + high) >>> 1;
+ Comparable<? super T> midVal = get(i, mid);
+ int cmp = midVal.compareTo(key);
+
+ if (cmp < 0)
+ low = mid + 1;
+ else if (cmp > 0)
+ high = mid - 1;
+ else
+ return mid; // key found
+ }
+ return -(low + 1); // key not found
+ }
+
+ /**
+ * Gets the ith element from the given list by repositioning the specified
+ * list listIterator.
+ */
+ private static <T> T get(ListIterator<? extends T> i, int index) {
+ T obj = null;
+ int pos = i.nextIndex();
+ if (pos <= index) {
+ do {
+ obj = i.next();
+ } while (pos++ < index);
+ } else {
+ do {
+ obj = i.previous();
+ } while (--pos > index);
+ }
+ return obj;
+ }
+
+ /**
+ * Searches the specified list for the specified object using the binary
+ * search algorithm. The list must be sorted into ascending order
+ * according to the specified comparator (as by the
+ * {@link #sort(List, Comparator) sort(List, Comparator)}
+ * method), prior to making this call. If it is
+ * not sorted, the results are undefined. If the list contains multiple
+ * elements equal to the specified object, there is no guarantee which one
+ * will be found.
+ *
+ * <p>This method runs in log(n) time for a "random access" list (which
+ * provides near-constant-time positional access). If the specified list
+ * does not implement the {@link RandomAccess} interface and is large,
+ * this method will do an iterator-based binary search that performs
+ * O(n) link traversals and O(log n) element comparisons.
+ *
+ * @param list the list to be searched.
+ * @param key the key to be searched for.
+ * @param c the comparator by which the list is ordered.
+ * A <tt>null</tt> value indicates that the elements'
+ * {@linkplain Comparable natural ordering} should be used.
+ * @return the index of the search key, if it is contained in the list;
+ * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The
+ * <i>insertion point</i> is defined as the point at which the
+ * key would be inserted into the list: the index of the first
+ * element greater than the key, or <tt>list.size()</tt> if all
+ * elements in the list are less than the specified key. Note
+ * that this guarantees that the return value will be >= 0 if
+ * and only if the key is found.
+ * @throws ClassCastException if the list contains elements that are not
+ * <i>mutually comparable</i> using the specified comparator,
+ * or the search key is not mutually comparable with the
+ * elements of the list using this comparator.
+ */
+ public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c) {
+ if (c==null)
+ return binarySearch((List) list, key);
+
+ if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
+ return Collections.indexedBinarySearch(list, key, c);
+ else
+ return Collections.iteratorBinarySearch(list, key, c);
+ }
+
+ private static <T> int indexedBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
+ int low = 0;
+ int high = l.size()-1;
+
+ while (low <= high) {
+ int mid = (low + high) >>> 1;
+ T midVal = l.get(mid);
+ int cmp = c.compare(midVal, key);
+
+ if (cmp < 0)
+ low = mid + 1;
+ else if (cmp > 0)
+ high = mid - 1;
+ else
+ return mid; // key found
+ }
+ return -(low + 1); // key not found
+ }
+
+ private static <T> int iteratorBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
+ int low = 0;
+ int high = l.size()-1;
+ ListIterator<? extends T> i = l.listIterator();
+
+ while (low <= high) {
+ int mid = (low + high) >>> 1;
+ T midVal = get(i, mid);
+ int cmp = c.compare(midVal, key);
+
+ if (cmp < 0)
+ low = mid + 1;
+ else if (cmp > 0)
+ high = mid - 1;
+ else
+ return mid; // key found
+ }
+ return -(low + 1); // key not found
+ }
+
+ private interface SelfComparable extends Comparable<SelfComparable> {}
+
+
+ /**
+ * Reverses the order of the elements in the specified list.<p>
+ *
+ * This method runs in linear time.
+ *
+ * @param list the list whose elements are to be reversed.
+ * @throws UnsupportedOperationException if the specified list or
+ * its list-iterator does not support the <tt>set</tt> operation.
+ */
+ public static void reverse(List<?> list) {
+ int size = list.size();
+ if (size < REVERSE_THRESHOLD || list instanceof RandomAccess) {
+ for (int i=0, mid=size>>1, j=size-1; i<mid; i++, j--)
+ swap(list, i, j);
+ } else {
+ ListIterator fwd = list.listIterator();
+ ListIterator rev = list.listIterator(size);
+ for (int i=0, mid=list.size()>>1; i<mid; i++) {
+ Object tmp = fwd.next();
+ fwd.set(rev.previous());
+ rev.set(tmp);
+ }
+ }
+ }
+
+ /**
+ * Randomly permutes the specified list using a default source of
+ * randomness. All permutations occur with approximately equal
+ * likelihood.<p>
+ *
+ * The hedge "approximately" is used in the foregoing description because
+ * default source of randomness is only approximately an unbiased source
+ * of independently chosen bits. If it were a perfect source of randomly
+ * chosen bits, then the algorithm would choose permutations with perfect
+ * uniformity.<p>
+ *
+ * This implementation traverses the list backwards, from the last element
+ * up to the second, repeatedly swapping a randomly selected element into
+ * the "current position". Elements are randomly selected from the
+ * portion of the list that runs from the first element to the current
+ * position, inclusive.<p>
+ *
+ * This method runs in linear time. If the specified list does not
+ * implement the {@link RandomAccess} interface and is large, this
+ * implementation dumps the specified list into an array before shuffling
+ * it, and dumps the shuffled array back into the list. This avoids the
+ * quadratic behavior that would result from shuffling a "sequential
+ * access" list in place.
+ *
+ * @param list the list to be shuffled.
+ * @throws UnsupportedOperationException if the specified list or
+ * its list-iterator does not support the <tt>set</tt> operation.
+ */
+ public static void shuffle(List<?> list) {
+ if (r == null) {
+ r = new Random();
+ }
+ shuffle(list, r);
+ }
+ private static Random r;
+
+ /**
+ * Randomly permute the specified list using the specified source of
+ * randomness. All permutations occur with equal likelihood
+ * assuming that the source of randomness is fair.<p>
+ *
+ * This implementation traverses the list backwards, from the last element
+ * up to the second, repeatedly swapping a randomly selected element into
+ * the "current position". Elements are randomly selected from the
+ * portion of the list that runs from the first element to the current
+ * position, inclusive.<p>
+ *
+ * This method runs in linear time. If the specified list does not
+ * implement the {@link RandomAccess} interface and is large, this
+ * implementation dumps the specified list into an array before shuffling
+ * it, and dumps the shuffled array back into the list. This avoids the
+ * quadratic behavior that would result from shuffling a "sequential
+ * access" list in place.
+ *
+ * @param list the list to be shuffled.
+ * @param rnd the source of randomness to use to shuffle the list.
+ * @throws UnsupportedOperationException if the specified list or its
+ * list-iterator does not support the <tt>set</tt> operation.
+ */
+ public static void shuffle(List<?> list, Random rnd) {
+ int size = list.size();
+ if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) {
+ for (int i=size; i>1; i--)
+ swap(list, i-1, rnd.nextInt(i));
+ } else {
+ Object arr[] = list.toArray();
+
+ // Shuffle array
+ for (int i=size; i>1; i--)
+ swap(arr, i-1, rnd.nextInt(i));
+
+ // Dump array back into list
+ ListIterator it = list.listIterator();
+ for (int i=0; i<arr.length; i++) {
+ it.next();
+ it.set(arr[i]);
+ }
+ }
+ }
+
+ /**
+ * Swaps the elements at the specified positions in the specified list.
+ * (If the specified positions are equal, invoking this method leaves
+ * the list unchanged.)
+ *
+ * @param list The list in which to swap elements.
+ * @param i the index of one element to be swapped.
+ * @param j the index of the other element to be swapped.
+ * @throws IndexOutOfBoundsException if either <tt>i</tt> or <tt>j</tt>
+ * is out of range (i < 0 || i >= list.size()
+ * || j < 0 || j >= list.size()).
+ * @since 1.4
+ */
+ public static void swap(List<?> list, int i, int j) {
+ final List l = list;
+ l.set(i, l.set(j, l.get(i)));
+ }
+
+ /**
+ * Swaps the two specified elements in the specified array.
+ */
+ private static void swap(Object[] arr, int i, int j) {
+ Object tmp = arr[i];
+ arr[i] = arr[j];
+ arr[j] = tmp;
+ }
+
+ /**
+ * Replaces all of the elements of the specified list with the specified
+ * element. <p>
+ *
+ * This method runs in linear time.
+ *
+ * @param list the list to be filled with the specified element.
+ * @param obj The element with which to fill the specified list.
+ * @throws UnsupportedOperationException if the specified list or its
+ * list-iterator does not support the <tt>set</tt> operation.
+ */
+ public static <T> void fill(List<? super T> list, T obj) {
+ int size = list.size();
+
+ if (size < FILL_THRESHOLD || list instanceof RandomAccess) {
+ for (int i=0; i<size; i++)
+ list.set(i, obj);
+ } else {
+ ListIterator<? super T> itr = list.listIterator();
+ for (int i=0; i<size; i++) {
+ itr.next();
+ itr.set(obj);
+ }
+ }
+ }
+
+ /**
+ * Copies all of the elements from one list into another. After the
+ * operation, the index of each copied element in the destination list
+ * will be identical to its index in the source list. The destination
+ * list must be at least as long as the source list. If it is longer, the
+ * remaining elements in the destination list are unaffected. <p>
+ *
+ * This method runs in linear time.
+ *
+ * @param dest The destination list.
+ * @param src The source list.
+ * @throws IndexOutOfBoundsException if the destination list is too small
+ * to contain the entire source List.
+ * @throws UnsupportedOperationException if the destination list's
+ * list-iterator does not support the <tt>set</tt> operation.
+ */
+ public static <T> void copy(List<? super T> dest, List<? extends T> src) {
+ int srcSize = src.size();
+ if (srcSize > dest.size())
+ throw new IndexOutOfBoundsException("Source does not fit in dest");
+
+ if (srcSize < COPY_THRESHOLD ||
+ (src instanceof RandomAccess && dest instanceof RandomAccess)) {
+ for (int i=0; i<srcSize; i++)
+ dest.set(i, src.get(i));
+ } else {
+ ListIterator<? super T> di=dest.listIterator();
+ ListIterator<? extends T> si=src.listIterator();
+ for (int i=0; i<srcSize; i++) {
+ di.next();
+ di.set(si.next());
+ }
+ }
+ }
+
+ /**
+ * Returns the minimum element of the given collection, according to the
+ * <i>natural ordering</i> of its elements. All elements in the
+ * collection must implement the <tt>Comparable</tt> interface.
+ * Furthermore, all elements in the collection must be <i>mutually
+ * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
+ * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
+ * <tt>e2</tt> in the collection).<p>
+ *
+ * This method iterates over the entire collection, hence it requires
+ * time proportional to the size of the collection.
+ *
+ * @param coll the collection whose minimum element is to be determined.
+ * @return the minimum element of the given collection, according
+ * to the <i>natural ordering</i> of its elements.
+ * @throws ClassCastException if the collection contains elements that are
+ * not <i>mutually comparable</i> (for example, strings and
+ * integers).
+ * @throws NoSuchElementException if the collection is empty.
+ * @see Comparable
+ */
+ public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll) {
+ Iterator<? extends T> i = coll.iterator();
+ T candidate = i.next();
+
+ while (i.hasNext()) {
+ T next = i.next();
+ if (next.compareTo(candidate) < 0)
+ candidate = next;
+ }
+ return candidate;
+ }
+
+ /**
+ * Returns the minimum element of the given collection, according to the
+ * order induced by the specified comparator. All elements in the
+ * collection must be <i>mutually comparable</i> by the specified
+ * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
+ * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
+ * <tt>e2</tt> in the collection).<p>
+ *
+ * This method iterates over the entire collection, hence it requires
+ * time proportional to the size of the collection.
+ *
+ * @param coll the collection whose minimum element is to be determined.
+ * @param comp the comparator with which to determine the minimum element.
+ * A <tt>null</tt> value indicates that the elements' <i>natural
+ * ordering</i> should be used.
+ * @return the minimum element of the given collection, according
+ * to the specified comparator.
+ * @throws ClassCastException if the collection contains elements that are
+ * not <i>mutually comparable</i> using the specified comparator.
+ * @throws NoSuchElementException if the collection is empty.
+ * @see Comparable
+ */
+ public static <T> T min(Collection<? extends T> coll, Comparator<? super T> comp) {
+ if (comp==null)
+ return (T)min((Collection<SelfComparable>) (Collection) coll);
+
+ Iterator<? extends T> i = coll.iterator();
+ T candidate = i.next();
+
+ while (i.hasNext()) {
+ T next = i.next();
+ if (comp.compare(next, candidate) < 0)
+ candidate = next;
+ }
+ return candidate;
+ }
+
+ /**
+ * Returns the maximum element of the given collection, according to the
+ * <i>natural ordering</i> of its elements. All elements in the
+ * collection must implement the <tt>Comparable</tt> interface.
+ * Furthermore, all elements in the collection must be <i>mutually
+ * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
+ * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
+ * <tt>e2</tt> in the collection).<p>
+ *
+ * This method iterates over the entire collection, hence it requires
+ * time proportional to the size of the collection.
+ *
+ * @param coll the collection whose maximum element is to be determined.
+ * @return the maximum element of the given collection, according
+ * to the <i>natural ordering</i> of its elements.
+ * @throws ClassCastException if the collection contains elements that are
+ * not <i>mutually comparable</i> (for example, strings and
+ * integers).
+ * @throws NoSuchElementException if the collection is empty.
+ * @see Comparable
+ */
+ public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) {
+ Iterator<? extends T> i = coll.iterator();
+ T candidate = i.next();
+
+ while (i.hasNext()) {
+ T next = i.next();
+ if (next.compareTo(candidate) > 0)
+ candidate = next;
+ }
+ return candidate;
+ }
+
+ /**
+ * Returns the maximum element of the given collection, according to the
+ * order induced by the specified comparator. All elements in the
+ * collection must be <i>mutually comparable</i> by the specified
+ * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
+ * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
+ * <tt>e2</tt> in the collection).<p>
+ *
+ * This method iterates over the entire collection, hence it requires
+ * time proportional to the size of the collection.
+ *
+ * @param coll the collection whose maximum element is to be determined.
+ * @param comp the comparator with which to determine the maximum element.
+ * A <tt>null</tt> value indicates that the elements' <i>natural
+ * ordering</i> should be used.
+ * @return the maximum element of the given collection, according
+ * to the specified comparator.
+ * @throws ClassCastException if the collection contains elements that are
+ * not <i>mutually comparable</i> using the specified comparator.
+ * @throws NoSuchElementException if the collection is empty.
+ * @see Comparable
+ */
+ public static <T> T max(Collection<? extends T> coll, Comparator<? super T> comp) {
+ if (comp==null)
+ return (T)max((Collection<SelfComparable>) (Collection) coll);
+
+ Iterator<? extends T> i = coll.iterator();
+ T candidate = i.next();
+
+ while (i.hasNext()) {
+ T next = i.next();
+ if (comp.compare(next, candidate) > 0)
+ candidate = next;
+ }
+ return candidate;
+ }
+
+ /**
+ * Rotates the elements in the specified list by the specified distance.
+ * After calling this method, the element at index <tt>i</tt> will be
+ * the element previously at index <tt>(i - distance)</tt> mod
+ * <tt>list.size()</tt>, for all values of <tt>i</tt> between <tt>0</tt>
+ * and <tt>list.size()-1</tt>, inclusive. (This method has no effect on
+ * the size of the list.)
+ *
+ * <p>For example, suppose <tt>list</tt> comprises<tt> [t, a, n, k, s]</tt>.
+ * After invoking <tt>Collections.rotate(list, 1)</tt> (or
+ * <tt>Collections.rotate(list, -4)</tt>), <tt>list</tt> will comprise
+ * <tt>[s, t, a, n, k]</tt>.
+ *
+ * <p>Note that this method can usefully be applied to sublists to
+ * move one or more elements within a list while preserving the
+ * order of the remaining elements. For example, the following idiom
+ * moves the element at index <tt>j</tt> forward to position
+ * <tt>k</tt> (which must be greater than or equal to <tt>j</tt>):
+ * <pre>
+ * Collections.rotate(list.subList(j, k+1), -1);
+ * </pre>
+ * To make this concrete, suppose <tt>list</tt> comprises
+ * <tt>[a, b, c, d, e]</tt>. To move the element at index <tt>1</tt>
+ * (<tt>b</tt>) forward two positions, perform the following invocation:
+ * <pre>
+ * Collections.rotate(l.subList(1, 4), -1);
+ * </pre>
+ * The resulting list is <tt>[a, c, d, b, e]</tt>.
+ *
+ * <p>To move more than one element forward, increase the absolute value
+ * of the rotation distance. To move elements backward, use a positive
+ * shift distance.
+ *
+ * <p>If the specified list is small or implements the {@link
+ * RandomAccess} interface, this implementation exchanges the first
+ * element into the location it should go, and then repeatedly exchanges
+ * the displaced element into the location it should go until a displaced
+ * element is swapped into the first element. If necessary, the process
+ * is repeated on the second and successive elements, until the rotation
+ * is complete. If the specified list is large and doesn't implement the
+ * <tt>RandomAccess</tt> interface, this implementation breaks the
+ * list into two sublist views around index <tt>-distance mod size</tt>.
+ * Then the {@link #reverse(List)} method is invoked on each sublist view,
+ * and finally it is invoked on the entire list. For a more complete
+ * description of both algorithms, see Section 2.3 of Jon Bentley's
+ * <i>Programming Pearls</i> (Addison-Wesley, 1986).
+ *
+ * @param list the list to be rotated.
+ * @param distance the distance to rotate the list. There are no
+ * constraints on this value; it may be zero, negative, or
+ * greater than <tt>list.size()</tt>.
+ * @throws UnsupportedOperationException if the specified list or
+ * its list-iterator does not support the <tt>set</tt> operation.
+ * @since 1.4
+ */
+ public static void rotate(List<?> list, int distance) {
+ if (list instanceof RandomAccess || list.size() < ROTATE_THRESHOLD)
+ rotate1(list, distance);
+ else
+ rotate2(list, distance);
+ }
+
+ private static <T> void rotate1(List<T> list, int distance) {
+ int size = list.size();
+ if (size == 0)
+ return;
+ distance = distance % size;
+ if (distance < 0)
+ distance += size;
+ if (distance == 0)
+ return;
+
+ for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) {
+ T displaced = list.get(cycleStart);
+ int i = cycleStart;
+ do {
+ i += distance;
+ if (i >= size)
+ i -= size;
+ displaced = list.set(i, displaced);
+ nMoved ++;
+ } while(i != cycleStart);
+ }
+ }
+
+ private static void rotate2(List<?> list, int distance) {
+ int size = list.size();
+ if (size == 0)
+ return;
+ int mid = -distance % size;
+ if (mid < 0)
+ mid += size;
+ if (mid == 0)
+ return;
+
+ reverse(list.subList(0, mid));
+ reverse(list.subList(mid, size));
+ reverse(list);
+ }
+
+ /**
+ * Replaces all occurrences of one specified value in a list with another.
+ * More formally, replaces with <tt>newVal</tt> each element <tt>e</tt>
+ * in <tt>list</tt> such that
+ * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>.
+ * (This method has no effect on the size of the list.)
+ *
+ * @param list the list in which replacement is to occur.
+ * @param oldVal the old value to be replaced.
+ * @param newVal the new value with which <tt>oldVal</tt> is to be
+ * replaced.
+ * @return <tt>true</tt> if <tt>list</tt> contained one or more elements
+ * <tt>e</tt> such that
+ * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>.
+ * @throws UnsupportedOperationException if the specified list or
+ * its list-iterator does not support the <tt>set</tt> operation.
+ * @since 1.4
+ */
+ public static <T> boolean replaceAll(List<T> list, T oldVal, T newVal) {
+ boolean result = false;
+ int size = list.size();
+ if (size < REPLACEALL_THRESHOLD || list instanceof RandomAccess) {
+ if (oldVal==null) {
+ for (int i=0; i<size; i++) {
+ if (list.get(i)==null) {
+ list.set(i, newVal);
+ result = true;
+ }
+ }
+ } else {
+ for (int i=0; i<size; i++) {
+ if (oldVal.equals(list.get(i))) {
+ list.set(i, newVal);
+ result = true;
+ }
+ }
+ }
+ } else {
+ ListIterator<T> itr=list.listIterator();
+ if (oldVal==null) {
+ for (int i=0; i<size; i++) {
+ if (itr.next()==null) {
+ itr.set(newVal);
+ result = true;
+ }
+ }
+ } else {
+ for (int i=0; i<size; i++) {
+ if (oldVal.equals(itr.next())) {
+ itr.set(newVal);
+ result = true;
+ }
+ }
+ }
+ }
+ return result;
+ }
+
+ /**
+ * Returns the starting position of the first occurrence of the specified
+ * target list within the specified source list, or -1 if there is no
+ * such occurrence. More formally, returns the lowest index <tt>i</tt>
+ * such that <tt>source.subList(i, i+target.size()).equals(target)</tt>,
+ * or -1 if there is no such index. (Returns -1 if
+ * <tt>target.size() > source.size()</tt>.)
+ *
+ * <p>This implementation uses the "brute force" technique of scanning
+ * over the source list, looking for a match with the target at each
+ * location in turn.
+ *
+ * @param source the list in which to search for the first occurrence
+ * of <tt>target</tt>.
+ * @param target the list to search for as a subList of <tt>source</tt>.
+ * @return the starting position of the first occurrence of the specified
+ * target list within the specified source list, or -1 if there
+ * is no such occurrence.
+ * @since 1.4
+ */
+ public static int indexOfSubList(List<?> source, List<?> target) {
+ int sourceSize = source.size();
+ int targetSize = target.size();
+ int maxCandidate = sourceSize - targetSize;
+
+ if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
+ (source instanceof RandomAccess&&target instanceof RandomAccess)) {
+ nextCand:
+ for (int candidate = 0; candidate <= maxCandidate; candidate++) {
+ for (int i=0, j=candidate; i<targetSize; i++, j++)
+ if (!eq(target.get(i), source.get(j)))
+ continue nextCand; // Element mismatch, try next cand
+ return candidate; // All elements of candidate matched target
+ }
+ } else { // Iterator version of above algorithm
+ ListIterator<?> si = source.listIterator();
+ nextCand:
+ for (int candidate = 0; candidate <= maxCandidate; candidate++) {
+ ListIterator<?> ti = target.listIterator();
+ for (int i=0; i<targetSize; i++) {
+ if (!eq(ti.next(), si.next())) {
+ // Back up source iterator to next candidate
+ for (int j=0; j<i; j++)
+ si.previous();
+ continue nextCand;
+ }
+ }
+ return candidate;
+ }
+ }
+ return -1; // No candidate matched the target
+ }
+
+ /**
+ * Returns the starting position of the last occurrence of the specified
+ * target list within the specified source list, or -1 if there is no such
+ * occurrence. More formally, returns the highest index <tt>i</tt>
+ * such that <tt>source.subList(i, i+target.size()).equals(target)</tt>,
+ * or -1 if there is no such index. (Returns -1 if
+ * <tt>target.size() > source.size()</tt>.)
+ *
+ * <p>This implementation uses the "brute force" technique of iterating
+ * over the source list, looking for a match with the target at each
+ * location in turn.
+ *
+ * @param source the list in which to search for the last occurrence
+ * of <tt>target</tt>.
+ * @param target the list to search for as a subList of <tt>source</tt>.
+ * @return the starting position of the last occurrence of the specified
+ * target list within the specified source list, or -1 if there
+ * is no such occurrence.
+ * @since 1.4
+ */
+ public static int lastIndexOfSubList(List<?> source, List<?> target) {
+ int sourceSize = source.size();
+ int targetSize = target.size();
+ int maxCandidate = sourceSize - targetSize;
+
+ if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
+ source instanceof RandomAccess) { // Index access version
+ nextCand:
+ for (int candidate = maxCandidate; candidate >= 0; candidate--) {
+ for (int i=0, j=candidate; i<targetSize; i++, j++)
+ if (!eq(target.get(i), source.get(j)))
+ continue nextCand; // Element mismatch, try next cand
+ return candidate; // All elements of candidate matched target
+ }
+ } else { // Iterator version of above algorithm
+ if (maxCandidate < 0)
+ return -1;
+ ListIterator<?> si = source.listIterator(maxCandidate);
+ nextCand:
+ for (int candidate = maxCandidate; candidate >= 0; candidate--) {
+ ListIterator<?> ti = target.listIterator();
+ for (int i=0; i<targetSize; i++) {
+ if (!eq(ti.next(), si.next())) {
+ if (candidate != 0) {
+ // Back up source iterator to next candidate
+ for (int j=0; j<=i+1; j++)
+ si.previous();
+ }
+ continue nextCand;
+ }
+ }
+ return candidate;
+ }
+ }
+ return -1; // No candidate matched the target
+ }
+
+
+ // Unmodifiable Wrappers
+
+ /**
+ * Returns an unmodifiable view of the specified collection. This method
+ * allows modules to provide users with "read-only" access to internal
+ * collections. Query operations on the returned collection "read through"
+ * to the specified collection, and attempts to modify the returned
+ * collection, whether direct or via its iterator, result in an
+ * <tt>UnsupportedOperationException</tt>.<p>
+ *
+ * The returned collection does <i>not</i> pass the hashCode and equals
+ * operations through to the backing collection, but relies on
+ * <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods. This
+ * is necessary to preserve the contracts of these operations in the case
+ * that the backing collection is a set or a list.<p>
+ *
+ * The returned collection will be serializable if the specified collection
+ * is serializable.
+ *
+ * @param c the collection for which an unmodifiable view is to be
+ * returned.
+ * @return an unmodifiable view of the specified collection.
+ */
+ public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) {
+ return new UnmodifiableCollection<T>(c);
+ }
+
+ /**
+ * @serial include
+ */
+ static class UnmodifiableCollection<E> implements Collection<E>, Serializable {
+ private static final long serialVersionUID = 1820017752578914078L;
+
+ final Collection<? extends E> c;
+
+ UnmodifiableCollection(Collection<? extends E> c) {
+ if (c==null)
+ throw new NullPointerException();
+ this.c = c;
+ }
+
+ public int size() {return c.size();}
+ public boolean isEmpty() {return c.isEmpty();}
+ public boolean contains(Object o) {return c.contains(o);}
+ public Object[] toArray() {return c.toArray();}
+ public <T> T[] toArray(T[] a) {return c.toArray(a);}
+ public String toString() {return c.toString();}
+
+ public Iterator<E> iterator() {
+ return new Iterator<E>() {
+ private final Iterator<? extends E> i = c.iterator();
+
+ public boolean hasNext() {return i.hasNext();}
+ public E next() {return i.next();}
+ public void remove() {
+ throw new UnsupportedOperationException();
+ }
+ };
+ }
+
+ public boolean add(E e) {
+ throw new UnsupportedOperationException();
+ }
+ public boolean remove(Object o) {
+ throw new UnsupportedOperationException();
+ }
+
+ public boolean containsAll(Collection<?> coll) {
+ return c.containsAll(coll);
+ }
+ public boolean addAll(Collection<? extends E> coll) {
+ throw new UnsupportedOperationException();
+ }
+ public boolean removeAll(Collection<?> coll) {
+ throw new UnsupportedOperationException();
+ }
+ public boolean retainAll(Collection<?> coll) {
+ throw new UnsupportedOperationException();
+ }
+ public void clear() {
+ throw new UnsupportedOperationException();
+ }
+ }
+
+ /**
+ * Returns an unmodifiable view of the specified set. This method allows
+ * modules to provide users with "read-only" access to internal sets.
+ * Query operations on the returned set "read through" to the specified
+ * set, and attempts to modify the returned set, whether direct or via its
+ * iterator, result in an <tt>UnsupportedOperationException</tt>.<p>
+ *
+ * The returned set will be serializable if the specified set
+ * is serializable.
+ *
+ * @param s the set for which an unmodifiable view is to be returned.
+ * @return an unmodifiable view of the specified set.
+ */
+ public static <T> Set<T> unmodifiableSet(Set<? extends T> s) {
+ return new UnmodifiableSet<T>(s);
+ }
+
+ /**
+ * @serial include
+ */
+ static class UnmodifiableSet<E> extends UnmodifiableCollection<E>
+ implements Set<E>, Serializable {
+ private static final long serialVersionUID = -9215047833775013803L;
+
+ UnmodifiableSet(Set<? extends E> s) {super(s);}
+ public boolean equals(Object o) {return o == this || c.equals(o);}
+ public int hashCode() {return c.hashCode();}
+ }
+
+ /**
+ * Returns an unmodifiable view of the specified sorted set. This method
+ * allows modules to provide users with "read-only" access to internal
+ * sorted sets. Query operations on the returned sorted set "read
+ * through" to the specified sorted set. Attempts to modify the returned
+ * sorted set, whether direct, via its iterator, or via its
+ * <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in
+ * an <tt>UnsupportedOperationException</tt>.<p>
+ *
+ * The returned sorted set will be serializable if the specified sorted set
+ * is serializable.
+ *
+ * @param s the sorted set for which an unmodifiable view is to be
+ * returned.
+ * @return an unmodifiable view of the specified sorted set.
+ */
+ public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) {
+ return new UnmodifiableSortedSet<T>(s);
+ }
+
+ /**
+ * @serial include
+ */
+ static class UnmodifiableSortedSet<E>
+ extends UnmodifiableSet<E>
+ implements SortedSet<E>, Serializable {
+ private static final long serialVersionUID = -4929149591599911165L;
+ private final SortedSet<E> ss;
+
+ UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;}
+
+ public Comparator<? super E> comparator() {return ss.comparator();}
+
+ public SortedSet<E> subSet(E fromElement, E toElement) {
+ return new UnmodifiableSortedSet<E>(ss.subSet(fromElement,toElement));
+ }
+ public SortedSet<E> headSet(E toElement) {
+ return new UnmodifiableSortedSet<E>(ss.headSet(toElement));
+ }
+ public SortedSet<E> tailSet(E fromElement) {
+ return new UnmodifiableSortedSet<E>(ss.tailSet(fromElement));
+ }
+
+ public E first() {return ss.first();}
+ public E last() {return ss.last();}
+ }
+
+ /**
+ * Returns an unmodifiable view of the specified list. This method allows
+ * modules to provide users with "read-only" access to internal
+ * lists. Query operations on the returned list "read through" to the
+ * specified list, and attempts to modify the returned list, whether
+ * direct or via its iterator, result in an
+ * <tt>UnsupportedOperationException</tt>.<p>
+ *
+ * The returned list will be serializable if the specified list
+ * is serializable. Similarly, the returned list will implement
+ * {@link RandomAccess} if the specified list does.
+ *
+ * @param list the list for which an unmodifiable view is to be returned.
+ * @return an unmodifiable view of the specified list.
+ */
+ public static <T> List<T> unmodifiableList(List<? extends T> list) {
+ return (list instanceof RandomAccess ?
+ new UnmodifiableRandomAccessList<T>(list) :
+ new UnmodifiableList<T>(list));
+ }
+
+ /**
+ * @serial include
+ */
+ static class UnmodifiableList<E> extends UnmodifiableCollection<E>
+ implements List<E> {
+ private static final long serialVersionUID = -283967356065247728L;
+ final List<? extends E> list;
+
+ UnmodifiableList(List<? extends E> list) {
+ super(list);
+ this.list = list;
+ }
+
+ public boolean equals(Object o) {return o == this || list.equals(o);}
+ public int hashCode() {return list.hashCode();}
+
+ public E get(int index) {return list.get(index);}
+ public E set(int index, E element) {
+ throw new UnsupportedOperationException();
+ }
+ public void add(int index, E element) {
+ throw new UnsupportedOperationException();
+ }
+ public E remove(int index) {
+ throw new UnsupportedOperationException();
+ }
+ public int indexOf(Object o) {return list.indexOf(o);}
+ public int lastIndexOf(Object o) {return list.lastIndexOf(o);}
+ public boolean addAll(int index, Collection<? extends E> c) {
+ throw new UnsupportedOperationException();
+ }
+ public ListIterator<E> listIterator() {return listIterator(0);}
+
+ public ListIterator<E> listIterator(final int index) {
+ return new ListIterator<E>() {
+ private final ListIterator<? extends E> i
+ = list.listIterator(index);
+
+ public boolean hasNext() {return i.hasNext();}
+ public E next() {return i.next();}
+ public boolean hasPrevious() {return i.hasPrevious();}
+ public E previous() {return i.previous();}
+ public int nextIndex() {return i.nextIndex();}
+ public int previousIndex() {return i.previousIndex();}
+
+ public void remove() {
+ throw new UnsupportedOperationException();
+ }
+ public void set(E e) {
+ throw new UnsupportedOperationException();
+ }
+ public void add(E e) {
+ throw new UnsupportedOperationException();
+ }
+ };
+ }
+
+ public List<E> subList(int fromIndex, int toIndex) {
+ return new UnmodifiableList<E>(list.subList(fromIndex, toIndex));
+ }
+
+ /**
+ * UnmodifiableRandomAccessList instances are serialized as
+ * UnmodifiableList instances to allow them to be deserialized
+ * in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList).
+ * This method inverts the transformation. As a beneficial
+ * side-effect, it also grafts the RandomAccess marker onto
+ * UnmodifiableList instances that were serialized in pre-1.4 JREs.
+ *
+ * Note: Unfortunately, UnmodifiableRandomAccessList instances
+ * serialized in 1.4.1 and deserialized in 1.4 will become
+ * UnmodifiableList instances, as this method was missing in 1.4.
+ */
+ private Object readResolve() {
+ return (list instanceof RandomAccess
+ ? new UnmodifiableRandomAccessList<E>(list)
+ : this);
+ }
+ }
+
+ /**
+ * @serial include
+ */
+ static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E>
+ implements RandomAccess
+ {
+ UnmodifiableRandomAccessList(List<? extends E> list) {
+ super(list);
+ }
+
+ public List<E> subList(int fromIndex, int toIndex) {
+ return new UnmodifiableRandomAccessList<E>(
+ list.subList(fromIndex, toIndex));
+ }
+
+ private static final long serialVersionUID = -2542308836966382001L;
+
+ /**
+ * Allows instances to be deserialized in pre-1.4 JREs (which do
+ * not have UnmodifiableRandomAccessList). UnmodifiableList has
+ * a readResolve method that inverts this transformation upon
+ * deserialization.
+ */
+ private Object writeReplace() {
+ return new UnmodifiableList<E>(list);
+ }
+ }
+
+ /**
+ * Returns an unmodifiable view of the specified map. This method
+ * allows modules to provide users with "read-only" access to internal
+ * maps. Query operations on the returned map "read through"
+ * to the specified map, and attempts to modify the returned
+ * map, whether direct or via its collection views, result in an
+ * <tt>UnsupportedOperationException</tt>.<p>
+ *
+ * The returned map will be serializable if the specified map
+ * is serializable.
+ *
+ * @param m the map for which an unmodifiable view is to be returned.
+ * @return an unmodifiable view of the specified map.
+ */
+ public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) {
+ return new UnmodifiableMap<K,V>(m);
+ }
+
+ /**
+ * @serial include
+ */
+ private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable {
+ private static final long serialVersionUID = -1034234728574286014L;
+
+ private final Map<? extends K, ? extends V> m;
+
+ UnmodifiableMap(Map<? extends K, ? extends V> m) {
+ if (m==null)
+ throw new NullPointerException();
+ this.m = m;
+ }
+
+ public int size() {return m.size();}
+ public boolean isEmpty() {return m.isEmpty();}
+ public boolean containsKey(Object key) {return m.containsKey(key);}
+ public boolean containsValue(Object val) {return m.containsValue(val);}
+ public V get(Object key) {return m.get(key);}
+
+ public V put(K key, V value) {
+ throw new UnsupportedOperationException();
+ }
+ public V remove(Object key) {
+ throw new UnsupportedOperationException();
+ }
+ public void putAll(Map<? extends K, ? extends V> m) {
+ throw new UnsupportedOperationException();
+ }
+ public void clear() {
+ throw new UnsupportedOperationException();
+ }
+
+ private transient Set<K> keySet = null;
+ private transient Set<Map.Entry<K,V>> entrySet = null;
+ private transient Collection<V> values = null;
+
+ public Set<K> keySet() {
+ if (keySet==null)
+ keySet = unmodifiableSet(m.keySet());
+ return keySet;
+ }
+
+ public Set<Map.Entry<K,V>> entrySet() {
+ if (entrySet==null)
+ entrySet = new UnmodifiableEntrySet<K,V>(m.entrySet());
+ return entrySet;
+ }
+
+ public Collection<V> values() {
+ if (values==null)
+ values = unmodifiableCollection(m.values());
+ return values;
+ }
+
+ public boolean equals(Object o) {return o == this || m.equals(o);}
+ public int hashCode() {return m.hashCode();}
+ public String toString() {return m.toString();}
+
+ /**
+ * We need this class in addition to UnmodifiableSet as
+ * Map.Entries themselves permit modification of the backing Map
+ * via their setValue operation. This class is subtle: there are
+ * many possible attacks that must be thwarted.
+ *
+ * @serial include
+ */
+ static class UnmodifiableEntrySet<K,V>
+ extends UnmodifiableSet<Map.Entry<K,V>> {
+ private static final long serialVersionUID = 7854390611657943733L;
+
+ UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) {
+ super((Set)s);
+ }
+ public Iterator<Map.Entry<K,V>> iterator() {
+ return new Iterator<Map.Entry<K,V>>() {
+ private final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator();
+
+ public boolean hasNext() {
+ return i.hasNext();
+ }
+ public Map.Entry<K,V> next() {
+ return new UnmodifiableEntry<K,V>(i.next());
+ }
+ public void remove() {
+ throw new UnsupportedOperationException();
+ }
+ };
+ }
+
+ public Object[] toArray() {
+ Object[] a = c.toArray();
+ for (int i=0; i<a.length; i++)
+ a[i] = new UnmodifiableEntry<K,V>((Map.Entry<K,V>)a[i]);
+ return a;
+ }
+
+ public <T> T[] toArray(T[] a) {
+ // We don't pass a to c.toArray, to avoid window of
+ // vulnerability wherein an unscrupulous multithreaded client
+ // could get his hands on raw (unwrapped) Entries from c.
+ Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
+
+ for (int i=0; i<arr.length; i++)
+ arr[i] = new UnmodifiableEntry<K,V>((Map.Entry<K,V>)arr[i]);
+
+ if (arr.length > a.length)
+ return (T[])arr;
+
+ System.arraycopy(arr, 0, a, 0, arr.length);
+ if (a.length > arr.length)
+ a[arr.length] = null;
+ return a;
+ }
+
+ /**
+ * This method is overridden to protect the backing set against
+ * an object with a nefarious equals function that senses
+ * that the equality-candidate is Map.Entry and calls its
+ * setValue method.
+ */
+ public boolean contains(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ return c.contains(
+ new UnmodifiableEntry<Object,Object>((Map.Entry<?,?>) o));
+ }
+
+ /**
+ * The next two methods are overridden to protect against
+ * an unscrupulous List whose contains(Object o) method senses
+ * when o is a Map.Entry, and calls o.setValue.
+ */
+ public boolean containsAll(Collection<?> coll) {
+ Iterator<?> e = coll.iterator();
+ while (e.hasNext())
+ if (!contains(e.next())) // Invokes safe contains() above
+ return false;
+ return true;
+ }
+ public boolean equals(Object o) {
+ if (o == this)
+ return true;
+
+ if (!(o instanceof Set))
+ return false;
+ Set s = (Set) o;
+ if (s.size() != c.size())
+ return false;
+ return containsAll(s); // Invokes safe containsAll() above
+ }
+
+ /**
+ * This "wrapper class" serves two purposes: it prevents
+ * the client from modifying the backing Map, by short-circuiting
+ * the setValue method, and it protects the backing Map against
+ * an ill-behaved Map.Entry that attempts to modify another
+ * Map Entry when asked to perform an equality check.
+ */
+ private static class UnmodifiableEntry<K,V> implements Map.Entry<K,V> {
+ private Map.Entry<? extends K, ? extends V> e;
+
+ UnmodifiableEntry(Map.Entry<? extends K, ? extends V> e) {this.e = e;}
+
+ public K getKey() {return e.getKey();}
+ public V getValue() {return e.getValue();}
+ public V setValue(V value) {
+ throw new UnsupportedOperationException();
+ }
+ public int hashCode() {return e.hashCode();}
+ public boolean equals(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ Map.Entry t = (Map.Entry)o;
+ return eq(e.getKey(), t.getKey()) &&
+ eq(e.getValue(), t.getValue());
+ }
+ public String toString() {return e.toString();}
+ }
+ }
+ }
+
+ /**
+ * Returns an unmodifiable view of the specified sorted map. This method
+ * allows modules to provide users with "read-only" access to internal
+ * sorted maps. Query operations on the returned sorted map "read through"
+ * to the specified sorted map. Attempts to modify the returned
+ * sorted map, whether direct, via its collection views, or via its
+ * <tt>subMap</tt>, <tt>headMap</tt>, or <tt>tailMap</tt> views, result in
+ * an <tt>UnsupportedOperationException</tt>.<p>
+ *
+ * The returned sorted map will be serializable if the specified sorted map
+ * is serializable.
+ *
+ * @param m the sorted map for which an unmodifiable view is to be
+ * returned.
+ * @return an unmodifiable view of the specified sorted map.
+ */
+ public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) {
+ return new UnmodifiableSortedMap<K,V>(m);
+ }
+
+ /**
+ * @serial include
+ */
+ static class UnmodifiableSortedMap<K,V>
+ extends UnmodifiableMap<K,V>
+ implements SortedMap<K,V>, Serializable {
+ private static final long serialVersionUID = -8806743815996713206L;
+
+ private final SortedMap<K, ? extends V> sm;
+
+ UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m;}
+
+ public Comparator<? super K> comparator() {return sm.comparator();}
+
+ public SortedMap<K,V> subMap(K fromKey, K toKey) {
+ return new UnmodifiableSortedMap<K,V>(sm.subMap(fromKey, toKey));
+ }
+ public SortedMap<K,V> headMap(K toKey) {
+ return new UnmodifiableSortedMap<K,V>(sm.headMap(toKey));
+ }
+ public SortedMap<K,V> tailMap(K fromKey) {
+ return new UnmodifiableSortedMap<K,V>(sm.tailMap(fromKey));
+ }
+
+ public K firstKey() {return sm.firstKey();}
+ public K lastKey() {return sm.lastKey();}
+ }
+
+
+ // Synch Wrappers
+
+ /**
+ * Returns a synchronized (thread-safe) collection backed by the specified
+ * collection. In order to guarantee serial access, it is critical that
+ * <strong>all</strong> access to the backing collection is accomplished
+ * through the returned collection.<p>
+ *
+ * It is imperative that the user manually synchronize on the returned
+ * collection when iterating over it:
+ * <pre>
+ * Collection c = Collections.synchronizedCollection(myCollection);
+ * ...
+ * synchronized(c) {
+ * Iterator i = c.iterator(); // Must be in the synchronized block
+ * while (i.hasNext())
+ * foo(i.next());
+ * }
+ * </pre>
+ * Failure to follow this advice may result in non-deterministic behavior.
+ *
+ * <p>The returned collection does <i>not</i> pass the <tt>hashCode</tt>
+ * and <tt>equals</tt> operations through to the backing collection, but
+ * relies on <tt>Object</tt>'s equals and hashCode methods. This is
+ * necessary to preserve the contracts of these operations in the case
+ * that the backing collection is a set or a list.<p>
+ *
+ * The returned collection will be serializable if the specified collection
+ * is serializable.
+ *
+ * @param c the collection to be "wrapped" in a synchronized collection.
+ * @return a synchronized view of the specified collection.
+ */
+ public static <T> Collection<T> synchronizedCollection(Collection<T> c) {
+ return new SynchronizedCollection<T>(c);
+ }
+
+ static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) {
+ return new SynchronizedCollection<T>(c, mutex);
+ }
+
+ /**
+ * @serial include
+ */
+ static class SynchronizedCollection<E> implements Collection<E>, Serializable {
+ private static final long serialVersionUID = 3053995032091335093L;
+
+ final Collection<E> c; // Backing Collection
+ final Object mutex; // Object on which to synchronize
+
+ SynchronizedCollection(Collection<E> c) {
+ if (c==null)
+ throw new NullPointerException();
+ this.c = c;
+ mutex = this;
+ }
+ SynchronizedCollection(Collection<E> c, Object mutex) {
+ this.c = c;
+ this.mutex = mutex;
+ }
+
+ public int size() {
+ synchronized(mutex) {return c.size();}
+ }
+ public boolean isEmpty() {
+ synchronized(mutex) {return c.isEmpty();}
+ }
+ public boolean contains(Object o) {
+ synchronized(mutex) {return c.contains(o);}
+ }
+ public Object[] toArray() {
+ synchronized(mutex) {return c.toArray();}
+ }
+ public <T> T[] toArray(T[] a) {
+ synchronized(mutex) {return c.toArray(a);}
+ }
+
+ public Iterator<E> iterator() {
+ return c.iterator(); // Must be manually synched by user!
+ }
+
+ public boolean add(E e) {
+ synchronized(mutex) {return c.add(e);}
+ }
+ public boolean remove(Object o) {
+ synchronized(mutex) {return c.remove(o);}
+ }
+
+ public boolean containsAll(Collection<?> coll) {
+ synchronized(mutex) {return c.containsAll(coll);}
+ }
+ public boolean addAll(Collection<? extends E> coll) {
+ synchronized(mutex) {return c.addAll(coll);}
+ }
+ public boolean removeAll(Collection<?> coll) {
+ synchronized(mutex) {return c.removeAll(coll);}
+ }
+ public boolean retainAll(Collection<?> coll) {
+ synchronized(mutex) {return c.retainAll(coll);}
+ }
+ public void clear() {
+ synchronized(mutex) {c.clear();}
+ }
+ public String toString() {
+ synchronized(mutex) {return c.toString();}
+ }
+ private void writeObject(ObjectOutputStream s) throws IOException {
+ synchronized(mutex) {s.defaultWriteObject();}
+ }
+ }
+
+ /**
+ * Returns a synchronized (thread-safe) set backed by the specified
+ * set. In order to guarantee serial access, it is critical that
+ * <strong>all</strong> access to the backing set is accomplished
+ * through the returned set.<p>
+ *
+ * It is imperative that the user manually synchronize on the returned
+ * set when iterating over it:
+ * <pre>
+ * Set s = Collections.synchronizedSet(new HashSet());
+ * ...
+ * synchronized(s) {
+ * Iterator i = s.iterator(); // Must be in the synchronized block
+ * while (i.hasNext())
+ * foo(i.next());
+ * }
+ * </pre>
+ * Failure to follow this advice may result in non-deterministic behavior.
+ *
+ * <p>The returned set will be serializable if the specified set is
+ * serializable.
+ *
+ * @param s the set to be "wrapped" in a synchronized set.
+ * @return a synchronized view of the specified set.
+ */
+ public static <T> Set<T> synchronizedSet(Set<T> s) {
+ return new SynchronizedSet<T>(s);
+ }
+
+ static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) {
+ return new SynchronizedSet<T>(s, mutex);
+ }
+
+ /**
+ * @serial include
+ */
+ static class SynchronizedSet<E>
+ extends SynchronizedCollection<E>
+ implements Set<E> {
+ private static final long serialVersionUID = 487447009682186044L;
+
+ SynchronizedSet(Set<E> s) {
+ super(s);
+ }
+ SynchronizedSet(Set<E> s, Object mutex) {
+ super(s, mutex);
+ }
+
+ public boolean equals(Object o) {
+ synchronized(mutex) {return c.equals(o);}
+ }
+ public int hashCode() {
+ synchronized(mutex) {return c.hashCode();}
+ }
+ }
+
+ /**
+ * Returns a synchronized (thread-safe) sorted set backed by the specified
+ * sorted set. In order to guarantee serial access, it is critical that
+ * <strong>all</strong> access to the backing sorted set is accomplished
+ * through the returned sorted set (or its views).<p>
+ *
+ * It is imperative that the user manually synchronize on the returned
+ * sorted set when iterating over it or any of its <tt>subSet</tt>,
+ * <tt>headSet</tt>, or <tt>tailSet</tt> views.
+ * <pre>
+ * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
+ * ...
+ * synchronized(s) {
+ * Iterator i = s.iterator(); // Must be in the synchronized block
+ * while (i.hasNext())
+ * foo(i.next());
+ * }
+ * </pre>
+ * or:
+ * <pre>
+ * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
+ * SortedSet s2 = s.headSet(foo);
+ * ...
+ * synchronized(s) { // Note: s, not s2!!!
+ * Iterator i = s2.iterator(); // Must be in the synchronized block
+ * while (i.hasNext())
+ * foo(i.next());
+ * }
+ * </pre>
+ * Failure to follow this advice may result in non-deterministic behavior.
+ *
+ * <p>The returned sorted set will be serializable if the specified
+ * sorted set is serializable.
+ *
+ * @param s the sorted set to be "wrapped" in a synchronized sorted set.
+ * @return a synchronized view of the specified sorted set.
+ */
+ public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) {
+ return new SynchronizedSortedSet<T>(s);
+ }
+
+ /**
+ * @serial include
+ */
+ static class SynchronizedSortedSet<E>
+ extends SynchronizedSet<E>
+ implements SortedSet<E>
+ {
+ private static final long serialVersionUID = 8695801310862127406L;
+
+ final private SortedSet<E> ss;
+
+ SynchronizedSortedSet(SortedSet<E> s) {
+ super(s);
+ ss = s;
+ }
+ SynchronizedSortedSet(SortedSet<E> s, Object mutex) {
+ super(s, mutex);
+ ss = s;
+ }
+
+ public Comparator<? super E> comparator() {
+ synchronized(mutex) {return ss.comparator();}
+ }
+
+ public SortedSet<E> subSet(E fromElement, E toElement) {
+ synchronized(mutex) {
+ return new SynchronizedSortedSet<E>(
+ ss.subSet(fromElement, toElement), mutex);
+ }
+ }
+ public SortedSet<E> headSet(E toElement) {
+ synchronized(mutex) {
+ return new SynchronizedSortedSet<E>(ss.headSet(toElement), mutex);
+ }
+ }
+ public SortedSet<E> tailSet(E fromElement) {
+ synchronized(mutex) {
+ return new SynchronizedSortedSet<E>(ss.tailSet(fromElement),mutex);
+ }
+ }
+
+ public E first() {
+ synchronized(mutex) {return ss.first();}
+ }
+ public E last() {
+ synchronized(mutex) {return ss.last();}
+ }
+ }
+
+ /**
+ * Returns a synchronized (thread-safe) list backed by the specified
+ * list. In order to guarantee serial access, it is critical that
+ * <strong>all</strong> access to the backing list is accomplished
+ * through the returned list.<p>
+ *
+ * It is imperative that the user manually synchronize on the returned
+ * list when iterating over it:
+ * <pre>
+ * List list = Collections.synchronizedList(new ArrayList());
+ * ...
+ * synchronized(list) {
+ * Iterator i = list.iterator(); // Must be in synchronized block
+ * while (i.hasNext())
+ * foo(i.next());
+ * }
+ * </pre>
+ * Failure to follow this advice may result in non-deterministic behavior.
+ *
+ * <p>The returned list will be serializable if the specified list is
+ * serializable.
+ *
+ * @param list the list to be "wrapped" in a synchronized list.
+ * @return a synchronized view of the specified list.
+ */
+ public static <T> List<T> synchronizedList(List<T> list) {
+ return (list instanceof RandomAccess ?
+ new SynchronizedRandomAccessList<T>(list) :
+ new SynchronizedList<T>(list));
+ }
+
+ static <T> List<T> synchronizedList(List<T> list, Object mutex) {
+ return (list instanceof RandomAccess ?
+ new SynchronizedRandomAccessList<T>(list, mutex) :
+ new SynchronizedList<T>(list, mutex));
+ }
+
+ /**
+ * @serial include
+ */
+ static class SynchronizedList<E>
+ extends SynchronizedCollection<E>
+ implements List<E> {
+ private static final long serialVersionUID = -7754090372962971524L;
+
+ final List<E> list;
+
+ SynchronizedList(List<E> list) {
+ super(list);
+ this.list = list;
+ }
+ SynchronizedList(List<E> list, Object mutex) {
+ super(list, mutex);
+ this.list = list;
+ }
+
+ public boolean equals(Object o) {
+ synchronized(mutex) {return list.equals(o);}
+ }
+ public int hashCode() {
+ synchronized(mutex) {return list.hashCode();}
+ }
+
+ public E get(int index) {
+ synchronized(mutex) {return list.get(index);}
+ }
+ public E set(int index, E element) {
+ synchronized(mutex) {return list.set(index, element);}
+ }
+ public void add(int index, E element) {
+ synchronized(mutex) {list.add(index, element);}
+ }
+ public E remove(int index) {
+ synchronized(mutex) {return list.remove(index);}
+ }
+
+ public int indexOf(Object o) {
+ synchronized(mutex) {return list.indexOf(o);}
+ }
+ public int lastIndexOf(Object o) {
+ synchronized(mutex) {return list.lastIndexOf(o);}
+ }
+
+ public boolean addAll(int index, Collection<? extends E> c) {
+ synchronized(mutex) {return list.addAll(index, c);}
+ }
+
+ public ListIterator<E> listIterator() {
+ return list.listIterator(); // Must be manually synched by user
+ }
+
+ public ListIterator<E> listIterator(int index) {
+ return list.listIterator(index); // Must be manually synched by user
+ }
+
+ public List<E> subList(int fromIndex, int toIndex) {
+ synchronized(mutex) {
+ return new SynchronizedList<E>(list.subList(fromIndex, toIndex),
+ mutex);
+ }
+ }
+
+ /**
+ * SynchronizedRandomAccessList instances are serialized as
+ * SynchronizedList instances to allow them to be deserialized
+ * in pre-1.4 JREs (which do not have SynchronizedRandomAccessList).
+ * This method inverts the transformation. As a beneficial
+ * side-effect, it also grafts the RandomAccess marker onto
+ * SynchronizedList instances that were serialized in pre-1.4 JREs.
+ *
+ * Note: Unfortunately, SynchronizedRandomAccessList instances
+ * serialized in 1.4.1 and deserialized in 1.4 will become
+ * SynchronizedList instances, as this method was missing in 1.4.
+ */
+ private Object readResolve() {
+ return (list instanceof RandomAccess
+ ? new SynchronizedRandomAccessList<E>(list)
+ : this);
+ }
+ }
+
+ /**
+ * @serial include
+ */
+ static class SynchronizedRandomAccessList<E>
+ extends SynchronizedList<E>
+ implements RandomAccess {
+
+ SynchronizedRandomAccessList(List<E> list) {
+ super(list);
+ }
+
+ SynchronizedRandomAccessList(List<E> list, Object mutex) {
+ super(list, mutex);
+ }
+
+ public List<E> subList(int fromIndex, int toIndex) {
+ synchronized(mutex) {
+ return new SynchronizedRandomAccessList<E>(
+ list.subList(fromIndex, toIndex), mutex);
+ }
+ }
+
+ private static final long serialVersionUID = 1530674583602358482L;
+
+ /**
+ * Allows instances to be deserialized in pre-1.4 JREs (which do
+ * not have SynchronizedRandomAccessList). SynchronizedList has
+ * a readResolve method that inverts this transformation upon
+ * deserialization.
+ */
+ private Object writeReplace() {
+ return new SynchronizedList<E>(list);
+ }
+ }
+
+ /**
+ * Returns a synchronized (thread-safe) map backed by the specified
+ * map. In order to guarantee serial access, it is critical that
+ * <strong>all</strong> access to the backing map is accomplished
+ * through the returned map.<p>
+ *
+ * It is imperative that the user manually synchronize on the returned
+ * map when iterating over any of its collection views:
+ * <pre>
+ * Map m = Collections.synchronizedMap(new HashMap());
+ * ...
+ * Set s = m.keySet(); // Needn't be in synchronized block
+ * ...
+ * synchronized(m) { // Synchronizing on m, not s!
+ * Iterator i = s.iterator(); // Must be in synchronized block
+ * while (i.hasNext())
+ * foo(i.next());
+ * }
+ * </pre>
+ * Failure to follow this advice may result in non-deterministic behavior.
+ *
+ * <p>The returned map will be serializable if the specified map is
+ * serializable.
+ *
+ * @param m the map to be "wrapped" in a synchronized map.
+ * @return a synchronized view of the specified map.
+ */
+ public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) {
+ return new SynchronizedMap<K,V>(m);
+ }
+
+ /**
+ * @serial include
+ */
+ private static class SynchronizedMap<K,V>
+ implements Map<K,V>, Serializable {
+ private static final long serialVersionUID = 1978198479659022715L;
+
+ private final Map<K,V> m; // Backing Map
+ final Object mutex; // Object on which to synchronize
+
+ SynchronizedMap(Map<K,V> m) {
+ if (m==null)
+ throw new NullPointerException();
+ this.m = m;
+ mutex = this;
+ }
+
+ SynchronizedMap(Map<K,V> m, Object mutex) {
+ this.m = m;
+ this.mutex = mutex;
+ }
+
+ public int size() {
+ synchronized(mutex) {return m.size();}
+ }
+ public boolean isEmpty() {
+ synchronized(mutex) {return m.isEmpty();}
+ }
+ public boolean containsKey(Object key) {
+ synchronized(mutex) {return m.containsKey(key);}
+ }
+ public boolean containsValue(Object value) {
+ synchronized(mutex) {return m.containsValue(value);}
+ }
+ public V get(Object key) {
+ synchronized(mutex) {return m.get(key);}
+ }
+
+ public V put(K key, V value) {
+ synchronized(mutex) {return m.put(key, value);}
+ }
+ public V remove(Object key) {
+ synchronized(mutex) {return m.remove(key);}
+ }
+ public void putAll(Map<? extends K, ? extends V> map) {
+ synchronized(mutex) {m.putAll(map);}
+ }
+ public void clear() {
+ synchronized(mutex) {m.clear();}
+ }
+
+ private transient Set<K> keySet = null;
+ private transient Set<Map.Entry<K,V>> entrySet = null;
+ private transient Collection<V> values = null;
+
+ public Set<K> keySet() {
+ synchronized(mutex) {
+ if (keySet==null)
+ keySet = new SynchronizedSet<K>(m.keySet(), mutex);
+ return keySet;
+ }
+ }
+
+ public Set<Map.Entry<K,V>> entrySet() {
+ synchronized(mutex) {
+ if (entrySet==null)
+ entrySet = new SynchronizedSet<Map.Entry<K,V>>(m.entrySet(), mutex);
+ return entrySet;
+ }
+ }
+
+ public Collection<V> values() {
+ synchronized(mutex) {
+ if (values==null)
+ values = new SynchronizedCollection<V>(m.values(), mutex);
+ return values;
+ }
+ }
+
+ public boolean equals(Object o) {
+ synchronized(mutex) {return m.equals(o);}
+ }
+ public int hashCode() {
+ synchronized(mutex) {return m.hashCode();}
+ }
+ public String toString() {
+ synchronized(mutex) {return m.toString();}
+ }
+ private void writeObject(ObjectOutputStream s) throws IOException {
+ synchronized(mutex) {s.defaultWriteObject();}
+ }
+ }
+
+ /**
+ * Returns a synchronized (thread-safe) sorted map backed by the specified
+ * sorted map. In order to guarantee serial access, it is critical that
+ * <strong>all</strong> access to the backing sorted map is accomplished
+ * through the returned sorted map (or its views).<p>
+ *
+ * It is imperative that the user manually synchronize on the returned
+ * sorted map when iterating over any of its collection views, or the
+ * collections views of any of its <tt>subMap</tt>, <tt>headMap</tt> or
+ * <tt>tailMap</tt> views.
+ * <pre>
+ * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
+ * ...
+ * Set s = m.keySet(); // Needn't be in synchronized block
+ * ...
+ * synchronized(m) { // Synchronizing on m, not s!
+ * Iterator i = s.iterator(); // Must be in synchronized block
+ * while (i.hasNext())
+ * foo(i.next());
+ * }
+ * </pre>
+ * or:
+ * <pre>
+ * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
+ * SortedMap m2 = m.subMap(foo, bar);
+ * ...
+ * Set s2 = m2.keySet(); // Needn't be in synchronized block
+ * ...
+ * synchronized(m) { // Synchronizing on m, not m2 or s2!
+ * Iterator i = s.iterator(); // Must be in synchronized block
+ * while (i.hasNext())
+ * foo(i.next());
+ * }
+ * </pre>
+ * Failure to follow this advice may result in non-deterministic behavior.
+ *
+ * <p>The returned sorted map will be serializable if the specified
+ * sorted map is serializable.
+ *
+ * @param m the sorted map to be "wrapped" in a synchronized sorted map.
+ * @return a synchronized view of the specified sorted map.
+ */
+ public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) {
+ return new SynchronizedSortedMap<K,V>(m);
+ }
+
+
+ /**
+ * @serial include
+ */
+ static class SynchronizedSortedMap<K,V>
+ extends SynchronizedMap<K,V>
+ implements SortedMap<K,V>
+ {
+ private static final long serialVersionUID = -8798146769416483793L;
+
+ private final SortedMap<K,V> sm;
+
+ SynchronizedSortedMap(SortedMap<K,V> m) {
+ super(m);
+ sm = m;
+ }
+ SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) {
+ super(m, mutex);
+ sm = m;
+ }
+
+ public Comparator<? super K> comparator() {
+ synchronized(mutex) {return sm.comparator();}
+ }
+
+ public SortedMap<K,V> subMap(K fromKey, K toKey) {
+ synchronized(mutex) {
+ return new SynchronizedSortedMap<K,V>(
+ sm.subMap(fromKey, toKey), mutex);
+ }
+ }
+ public SortedMap<K,V> headMap(K toKey) {
+ synchronized(mutex) {
+ return new SynchronizedSortedMap<K,V>(sm.headMap(toKey), mutex);
+ }
+ }
+ public SortedMap<K,V> tailMap(K fromKey) {
+ synchronized(mutex) {
+ return new SynchronizedSortedMap<K,V>(sm.tailMap(fromKey),mutex);
+ }
+ }
+
+ public K firstKey() {
+ synchronized(mutex) {return sm.firstKey();}
+ }
+ public K lastKey() {
+ synchronized(mutex) {return sm.lastKey();}
+ }
+ }
+
+ // Dynamically typesafe collection wrappers
+
+ /**
+ * Returns a dynamically typesafe view of the specified collection.
+ * Any attempt to insert an element of the wrong type will result in an
+ * immediate {@link ClassCastException}. Assuming a collection
+ * contains no incorrectly typed elements prior to the time a
+ * dynamically typesafe view is generated, and that all subsequent
+ * access to the collection takes place through the view, it is
+ * <i>guaranteed</i> that the collection cannot contain an incorrectly
+ * typed element.
+ *
+ * <p>The generics mechanism in the language provides compile-time
+ * (static) type checking, but it is possible to defeat this mechanism
+ * with unchecked casts. Usually this is not a problem, as the compiler
+ * issues warnings on all such unchecked operations. There are, however,
+ * times when static type checking alone is not sufficient. For example,
+ * suppose a collection is passed to a third-party library and it is
+ * imperative that the library code not corrupt the collection by
+ * inserting an element of the wrong type.
+ *
+ * <p>Another use of dynamically typesafe views is debugging. Suppose a
+ * program fails with a {@code ClassCastException}, indicating that an
+ * incorrectly typed element was put into a parameterized collection.
+ * Unfortunately, the exception can occur at any time after the erroneous
+ * element is inserted, so it typically provides little or no information
+ * as to the real source of the problem. If the problem is reproducible,
+ * one can quickly determine its source by temporarily modifying the
+ * program to wrap the collection with a dynamically typesafe view.
+ * For example, this declaration:
+ * <pre> {@code
+ * Collection<String> c = new HashSet<String>();
+ * }</pre>
+ * may be replaced temporarily by this one:
+ * <pre> {@code
+ * Collection<String> c = Collections.checkedCollection(
+ * new HashSet<String>(), String.class);
+ * }</pre>
+ * Running the program again will cause it to fail at the point where
+ * an incorrectly typed element is inserted into the collection, clearly
+ * identifying the source of the problem. Once the problem is fixed, the
+ * modified declaration may be reverted back to the original.
+ *
+ * <p>The returned collection does <i>not</i> pass the hashCode and equals
+ * operations through to the backing collection, but relies on
+ * {@code Object}'s {@code equals} and {@code hashCode} methods. This
+ * is necessary to preserve the contracts of these operations in the case
+ * that the backing collection is a set or a list.
+ *
+ * <p>The returned collection will be serializable if the specified
+ * collection is serializable.
+ *
+ * <p>Since {@code null} is considered to be a value of any reference
+ * type, the returned collection permits insertion of null elements
+ * whenever the backing collection does.
+ *
+ * @param c the collection for which a dynamically typesafe view is to be
+ * returned
+ * @param type the type of element that {@code c} is permitted to hold
+ * @return a dynamically typesafe view of the specified collection
+ * @since 1.5
+ */
+ public static <E> Collection<E> checkedCollection(Collection<E> c,
+ Class<E> type) {
+ return new CheckedCollection<E>(c, type);
+ }
+
+ @SuppressWarnings("unchecked")
+ static <T> T[] zeroLengthArray(Class<T> type) {
+ return (T[]) Array.newInstance(type, 0);
+ }
+
+ /**
+ * @serial include
+ */
+ static class CheckedCollection<E> implements Collection<E>, Serializable {
+ private static final long serialVersionUID = 1578914078182001775L;
+
+ final Collection<E> c;
+ final Class<E> type;
+
+ void typeCheck(Object o) {
+ if (o != null && !type.isInstance(o))
+ throw new ClassCastException(badElementMsg(o));
+ }
+
+ private String badElementMsg(Object o) {
+ return "Attempt to insert " + o.getClass() +
+ " element into collection with element type " + type;
+ }
+
+ CheckedCollection(Collection<E> c, Class<E> type) {
+ if (c==null || type == null)
+ throw new NullPointerException();
+ this.c = c;
+ this.type = type;
+ }
+
+ public int size() { return c.size(); }
+ public boolean isEmpty() { return c.isEmpty(); }
+ public boolean contains(Object o) { return c.contains(o); }
+ public Object[] toArray() { return c.toArray(); }
+ public <T> T[] toArray(T[] a) { return c.toArray(a); }
+ public String toString() { return c.toString(); }
+ public boolean remove(Object o) { return c.remove(o); }
+ public void clear() { c.clear(); }
+
+ public boolean containsAll(Collection<?> coll) {
+ return c.containsAll(coll);
+ }
+ public boolean removeAll(Collection<?> coll) {
+ return c.removeAll(coll);
+ }
+ public boolean retainAll(Collection<?> coll) {
+ return c.retainAll(coll);
+ }
+
+ public Iterator<E> iterator() {
+ final Iterator<E> it = c.iterator();
+ return new Iterator<E>() {
+ public boolean hasNext() { return it.hasNext(); }
+ public E next() { return it.next(); }
+ public void remove() { it.remove(); }};
+ }
+
+ public boolean add(E e) {
+ typeCheck(e);
+ return c.add(e);
+ }
+
+ private E[] zeroLengthElementArray = null; // Lazily initialized
+
+ private E[] zeroLengthElementArray() {
+ return zeroLengthElementArray != null ? zeroLengthElementArray :
+ (zeroLengthElementArray = zeroLengthArray(type));
+ }
+
+ @SuppressWarnings("unchecked")
+ Collection<E> checkedCopyOf(Collection<? extends E> coll) {
+ Object[] a = null;
+ try {
+ E[] z = zeroLengthElementArray();
+ a = coll.toArray(z);
+ // Defend against coll violating the toArray contract
+ if (a.getClass() != z.getClass())
+ a = Arrays.copyOf(a, a.length, z.getClass());
+ } catch (ArrayStoreException ignore) {
+ // To get better and consistent diagnostics,
+ // we call typeCheck explicitly on each element.
+ // We call clone() to defend against coll retaining a
+ // reference to the returned array and storing a bad
+ // element into it after it has been type checked.
+ a = coll.toArray().clone();
+ for (Object o : a)
+ typeCheck(o);
+ }
+ // A slight abuse of the type system, but safe here.
+ return (Collection<E>) Arrays.asList(a);
+ }
+
+ public boolean addAll(Collection<? extends E> coll) {
+ // Doing things this way insulates us from concurrent changes
+ // in the contents of coll and provides all-or-nothing
+ // semantics (which we wouldn't get if we type-checked each
+ // element as we added it)
+ return c.addAll(checkedCopyOf(coll));
+ }
+ }
+
+ /**
+ * Returns a dynamically typesafe view of the specified set.
+ * Any attempt to insert an element of the wrong type will result in
+ * an immediate {@link ClassCastException}. Assuming a set contains
+ * no incorrectly typed elements prior to the time a dynamically typesafe
+ * view is generated, and that all subsequent access to the set
+ * takes place through the view, it is <i>guaranteed</i> that the
+ * set cannot contain an incorrectly typed element.
+ *
+ * <p>A discussion of the use of dynamically typesafe views may be
+ * found in the documentation for the {@link #checkedCollection
+ * checkedCollection} method.
+ *
+ * <p>The returned set will be serializable if the specified set is
+ * serializable.
+ *
+ * <p>Since {@code null} is considered to be a value of any reference
+ * type, the returned set permits insertion of null elements whenever
+ * the backing set does.
+ *
+ * @param s the set for which a dynamically typesafe view is to be
+ * returned
+ * @param type the type of element that {@code s} is permitted to hold
+ * @return a dynamically typesafe view of the specified set
+ * @since 1.5
+ */
+ public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) {
+ return new CheckedSet<E>(s, type);
+ }
+
+ /**
+ * @serial include
+ */
+ static class CheckedSet<E> extends CheckedCollection<E>
+ implements Set<E>, Serializable
+ {
+ private static final long serialVersionUID = 4694047833775013803L;
+
+ CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); }
+
+ public boolean equals(Object o) { return o == this || c.equals(o); }
+ public int hashCode() { return c.hashCode(); }
+ }
+
+ /**
+ * Returns a dynamically typesafe view of the specified sorted set.
+ * Any attempt to insert an element of the wrong type will result in an
+ * immediate {@link ClassCastException}. Assuming a sorted set
+ * contains no incorrectly typed elements prior to the time a
+ * dynamically typesafe view is generated, and that all subsequent
+ * access to the sorted set takes place through the view, it is
+ * <i>guaranteed</i> that the sorted set cannot contain an incorrectly
+ * typed element.
+ *
+ * <p>A discussion of the use of dynamically typesafe views may be
+ * found in the documentation for the {@link #checkedCollection
+ * checkedCollection} method.
+ *
+ * <p>The returned sorted set will be serializable if the specified sorted
+ * set is serializable.
+ *
+ * <p>Since {@code null} is considered to be a value of any reference
+ * type, the returned sorted set permits insertion of null elements
+ * whenever the backing sorted set does.
+ *
+ * @param s the sorted set for which a dynamically typesafe view is to be
+ * returned
+ * @param type the type of element that {@code s} is permitted to hold
+ * @return a dynamically typesafe view of the specified sorted set
+ * @since 1.5
+ */
+ public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s,
+ Class<E> type) {
+ return new CheckedSortedSet<E>(s, type);
+ }
+
+ /**
+ * @serial include
+ */
+ static class CheckedSortedSet<E> extends CheckedSet<E>
+ implements SortedSet<E>, Serializable
+ {
+ private static final long serialVersionUID = 1599911165492914959L;
+ private final SortedSet<E> ss;
+
+ CheckedSortedSet(SortedSet<E> s, Class<E> type) {
+ super(s, type);
+ ss = s;
+ }
+
+ public Comparator<? super E> comparator() { return ss.comparator(); }
+ public E first() { return ss.first(); }
+ public E last() { return ss.last(); }
+
+ public SortedSet<E> subSet(E fromElement, E toElement) {
+ return checkedSortedSet(ss.subSet(fromElement,toElement), type);
+ }
+ public SortedSet<E> headSet(E toElement) {
+ return checkedSortedSet(ss.headSet(toElement), type);
+ }
+ public SortedSet<E> tailSet(E fromElement) {
+ return checkedSortedSet(ss.tailSet(fromElement), type);
+ }
+ }
+
+ /**
+ * Returns a dynamically typesafe view of the specified list.
+ * Any attempt to insert an element of the wrong type will result in
+ * an immediate {@link ClassCastException}. Assuming a list contains
+ * no incorrectly typed elements prior to the time a dynamically typesafe
+ * view is generated, and that all subsequent access to the list
+ * takes place through the view, it is <i>guaranteed</i> that the
+ * list cannot contain an incorrectly typed element.
+ *
+ * <p>A discussion of the use of dynamically typesafe views may be
+ * found in the documentation for the {@link #checkedCollection
+ * checkedCollection} method.
+ *
+ * <p>The returned list will be serializable if the specified list
+ * is serializable.
+ *
+ * <p>Since {@code null} is considered to be a value of any reference
+ * type, the returned list permits insertion of null elements whenever
+ * the backing list does.
+ *
+ * @param list the list for which a dynamically typesafe view is to be
+ * returned
+ * @param type the type of element that {@code list} is permitted to hold
+ * @return a dynamically typesafe view of the specified list
+ * @since 1.5
+ */
+ public static <E> List<E> checkedList(List<E> list, Class<E> type) {
+ return (list instanceof RandomAccess ?
+ new CheckedRandomAccessList<E>(list, type) :
+ new CheckedList<E>(list, type));
+ }
+
+ /**
+ * @serial include
+ */
+ static class CheckedList<E>
+ extends CheckedCollection<E>
+ implements List<E>
+ {
+ private static final long serialVersionUID = 65247728283967356L;
+ final List<E> list;
+
+ CheckedList(List<E> list, Class<E> type) {
+ super(list, type);
+ this.list = list;
+ }
+
+ public boolean equals(Object o) { return o == this || list.equals(o); }
+ public int hashCode() { return list.hashCode(); }
+ public E get(int index) { return list.get(index); }
+ public E remove(int index) { return list.remove(index); }
+ public int indexOf(Object o) { return list.indexOf(o); }
+ public int lastIndexOf(Object o) { return list.lastIndexOf(o); }
+
+ public E set(int index, E element) {
+ typeCheck(element);
+ return list.set(index, element);
+ }
+
+ public void add(int index, E element) {
+ typeCheck(element);
+ list.add(index, element);
+ }
+
+ public boolean addAll(int index, Collection<? extends E> c) {
+ return list.addAll(index, checkedCopyOf(c));
+ }
+ public ListIterator<E> listIterator() { return listIterator(0); }
+
+ public ListIterator<E> listIterator(final int index) {
+ final ListIterator<E> i = list.listIterator(index);
+
+ return new ListIterator<E>() {
+ public boolean hasNext() { return i.hasNext(); }
+ public E next() { return i.next(); }
+ public boolean hasPrevious() { return i.hasPrevious(); }
+ public E previous() { return i.previous(); }
+ public int nextIndex() { return i.nextIndex(); }
+ public int previousIndex() { return i.previousIndex(); }
+ public void remove() { i.remove(); }
+
+ public void set(E e) {
+ typeCheck(e);
+ i.set(e);
+ }
+
+ public void add(E e) {
+ typeCheck(e);
+ i.add(e);
+ }
+ };
+ }
+
+ public List<E> subList(int fromIndex, int toIndex) {
+ return new CheckedList<E>(list.subList(fromIndex, toIndex), type);
+ }
+ }
+
+ /**
+ * @serial include
+ */
+ static class CheckedRandomAccessList<E> extends CheckedList<E>
+ implements RandomAccess
+ {
+ private static final long serialVersionUID = 1638200125423088369L;
+
+ CheckedRandomAccessList(List<E> list, Class<E> type) {
+ super(list, type);
+ }
+
+ public List<E> subList(int fromIndex, int toIndex) {
+ return new CheckedRandomAccessList<E>(
+ list.subList(fromIndex, toIndex), type);
+ }
+ }
+
+ /**
+ * Returns a dynamically typesafe view of the specified map.
+ * Any attempt to insert a mapping whose key or value have the wrong
+ * type will result in an immediate {@link ClassCastException}.
+ * Similarly, any attempt to modify the value currently associated with
+ * a key will result in an immediate {@link ClassCastException},
+ * whether the modification is attempted directly through the map
+ * itself, or through a {@link Map.Entry} instance obtained from the
+ * map's {@link Map#entrySet() entry set} view.
+ *
+ * <p>Assuming a map contains no incorrectly typed keys or values
+ * prior to the time a dynamically typesafe view is generated, and
+ * that all subsequent access to the map takes place through the view
+ * (or one of its collection views), it is <i>guaranteed</i> that the
+ * map cannot contain an incorrectly typed key or value.
+ *
+ * <p>A discussion of the use of dynamically typesafe views may be
+ * found in the documentation for the {@link #checkedCollection
+ * checkedCollection} method.
+ *
+ * <p>The returned map will be serializable if the specified map is
+ * serializable.
+ *
+ * <p>Since {@code null} is considered to be a value of any reference
+ * type, the returned map permits insertion of null keys or values
+ * whenever the backing map does.
+ *
+ * @param m the map for which a dynamically typesafe view is to be
+ * returned
+ * @param keyType the type of key that {@code m} is permitted to hold
+ * @param valueType the type of value that {@code m} is permitted to hold
+ * @return a dynamically typesafe view of the specified map
+ * @since 1.5
+ */
+ public static <K, V> Map<K, V> checkedMap(Map<K, V> m,
+ Class<K> keyType,
+ Class<V> valueType) {
+ return new CheckedMap<K,V>(m, keyType, valueType);
+ }
+
+
+ /**
+ * @serial include
+ */
+ private static class CheckedMap<K,V>
+ implements Map<K,V>, Serializable
+ {
+ private static final long serialVersionUID = 5742860141034234728L;
+
+ private final Map<K, V> m;
+ final Class<K> keyType;
+ final Class<V> valueType;
+
+ private void typeCheck(Object key, Object value) {
+ if (key != null && !keyType.isInstance(key))
+ throw new ClassCastException(badKeyMsg(key));
+
+ if (value != null && !valueType.isInstance(value))
+ throw new ClassCastException(badValueMsg(value));
+ }
+
+ private String badKeyMsg(Object key) {
+ return "Attempt to insert " + key.getClass() +
+ " key into map with key type " + keyType;
+ }
+
+ private String badValueMsg(Object value) {
+ return "Attempt to insert " + value.getClass() +
+ " value into map with value type " + valueType;
+ }
+
+ CheckedMap(Map<K, V> m, Class<K> keyType, Class<V> valueType) {
+ if (m == null || keyType == null || valueType == null)
+ throw new NullPointerException();
+ this.m = m;
+ this.keyType = keyType;
+ this.valueType = valueType;
+ }
+
+ public int size() { return m.size(); }
+ public boolean isEmpty() { return m.isEmpty(); }
+ public boolean containsKey(Object key) { return m.containsKey(key); }
+ public boolean containsValue(Object v) { return m.containsValue(v); }
+ public V get(Object key) { return m.get(key); }
+ public V remove(Object key) { return m.remove(key); }
+ public void clear() { m.clear(); }
+ public Set<K> keySet() { return m.keySet(); }
+ public Collection<V> values() { return m.values(); }
+ public boolean equals(Object o) { return o == this || m.equals(o); }
+ public int hashCode() { return m.hashCode(); }
+ public String toString() { return m.toString(); }
+
+ public V put(K key, V value) {
+ typeCheck(key, value);
+ return m.put(key, value);
+ }
+
+ @SuppressWarnings("unchecked")
+ public void putAll(Map<? extends K, ? extends V> t) {
+ // Satisfy the following goals:
+ // - good diagnostics in case of type mismatch
+ // - all-or-nothing semantics
+ // - protection from malicious t
+ // - correct behavior if t is a concurrent map
+ Object[] entries = t.entrySet().toArray();
+ List<Map.Entry<K,V>> checked =
+ new ArrayList<Map.Entry<K,V>>(entries.length);
+ for (Object o : entries) {
+ Map.Entry<?,?> e = (Map.Entry<?,?>) o;
+ Object k = e.getKey();
+ Object v = e.getValue();
+ typeCheck(k, v);
+ checked.add(
+ new AbstractMap.SimpleImmutableEntry<K,V>((K) k, (V) v));
+ }
+ for (Map.Entry<K,V> e : checked)
+ m.put(e.getKey(), e.getValue());
+ }
+
+ private transient Set<Map.Entry<K,V>> entrySet = null;
+
+ public Set<Map.Entry<K,V>> entrySet() {
+ if (entrySet==null)
+ entrySet = new CheckedEntrySet<K,V>(m.entrySet(), valueType);
+ return entrySet;
+ }
+
+ /**
+ * We need this class in addition to CheckedSet as Map.Entry permits
+ * modification of the backing Map via the setValue operation. This
+ * class is subtle: there are many possible attacks that must be
+ * thwarted.
+ *
+ * @serial exclude
+ */
+ static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> {
+ private final Set<Map.Entry<K,V>> s;
+ private final Class<V> valueType;
+
+ CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) {
+ this.s = s;
+ this.valueType = valueType;
+ }
+
+ public int size() { return s.size(); }
+ public boolean isEmpty() { return s.isEmpty(); }
+ public String toString() { return s.toString(); }
+ public int hashCode() { return s.hashCode(); }
+ public void clear() { s.clear(); }
+
+ public boolean add(Map.Entry<K, V> e) {
+ throw new UnsupportedOperationException();
+ }
+ public boolean addAll(Collection<? extends Map.Entry<K, V>> coll) {
+ throw new UnsupportedOperationException();
+ }
+
+ public Iterator<Map.Entry<K,V>> iterator() {
+ final Iterator<Map.Entry<K, V>> i = s.iterator();
+ final Class<V> valueType = this.valueType;
+
+ return new Iterator<Map.Entry<K,V>>() {
+ public boolean hasNext() { return i.hasNext(); }
+ public void remove() { i.remove(); }
+
+ public Map.Entry<K,V> next() {
+ return checkedEntry(i.next(), valueType);
+ }
+ };
+ }
+
+ @SuppressWarnings("unchecked")
+ public Object[] toArray() {
+ Object[] source = s.toArray();
+
+ /*
+ * Ensure that we don't get an ArrayStoreException even if
+ * s.toArray returns an array of something other than Object
+ */
+ Object[] dest = (CheckedEntry.class.isInstance(
+ source.getClass().getComponentType()) ? source :
+ new Object[source.length]);
+
+ for (int i = 0; i < source.length; i++)
+ dest[i] = checkedEntry((Map.Entry<K,V>)source[i],
+ valueType);
+ return dest;
+ }
+
+ @SuppressWarnings("unchecked")
+ public <T> T[] toArray(T[] a) {
+ // We don't pass a to s.toArray, to avoid window of
+ // vulnerability wherein an unscrupulous multithreaded client
+ // could get his hands on raw (unwrapped) Entries from s.
+ T[] arr = s.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
+
+ for (int i=0; i<arr.length; i++)
+ arr[i] = (T) checkedEntry((Map.Entry<K,V>)arr[i],
+ valueType);
+ if (arr.length > a.length)
+ return arr;
+
+ System.arraycopy(arr, 0, a, 0, arr.length);
+ if (a.length > arr.length)
+ a[arr.length] = null;
+ return a;
+ }
+
+ /**
+ * This method is overridden to protect the backing set against
+ * an object with a nefarious equals function that senses
+ * that the equality-candidate is Map.Entry and calls its
+ * setValue method.
+ */
+ public boolean contains(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ Map.Entry<?,?> e = (Map.Entry<?,?>) o;
+ return s.contains(
+ (e instanceof CheckedEntry) ? e : checkedEntry(e, valueType));
+ }
+
+ /**
+ * The bulk collection methods are overridden to protect
+ * against an unscrupulous collection whose contains(Object o)
+ * method senses when o is a Map.Entry, and calls o.setValue.
+ */
+ public boolean containsAll(Collection<?> c) {
+ for (Object o : c)
+ if (!contains(o)) // Invokes safe contains() above
+ return false;
+ return true;
+ }
+
+ public boolean remove(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ return s.remove(new AbstractMap.SimpleImmutableEntry
+ <Object, Object>((Map.Entry<?,?>)o));
+ }
+
+ public boolean removeAll(Collection<?> c) {
+ return batchRemove(c, false);
+ }
+ public boolean retainAll(Collection<?> c) {
+ return batchRemove(c, true);
+ }
+ private boolean batchRemove(Collection<?> c, boolean complement) {
+ boolean modified = false;
+ Iterator<Map.Entry<K,V>> it = iterator();
+ while (it.hasNext()) {
+ if (c.contains(it.next()) != complement) {
+ it.remove();
+ modified = true;
+ }
+ }
+ return modified;
+ }
+
+ public boolean equals(Object o) {
+ if (o == this)
+ return true;
+ if (!(o instanceof Set))
+ return false;
+ Set<?> that = (Set<?>) o;
+ return that.size() == s.size()
+ && containsAll(that); // Invokes safe containsAll() above
+ }
+
+ static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e,
+ Class<T> valueType) {
+ return new CheckedEntry<K,V,T>(e, valueType);
+ }
+
+ /**
+ * This "wrapper class" serves two purposes: it prevents
+ * the client from modifying the backing Map, by short-circuiting
+ * the setValue method, and it protects the backing Map against
+ * an ill-behaved Map.Entry that attempts to modify another
+ * Map.Entry when asked to perform an equality check.
+ */
+ private static class CheckedEntry<K,V,T> implements Map.Entry<K,V> {
+ private final Map.Entry<K, V> e;
+ private final Class<T> valueType;
+
+ CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) {
+ this.e = e;
+ this.valueType = valueType;
+ }
+
+ public K getKey() { return e.getKey(); }
+ public V getValue() { return e.getValue(); }
+ public int hashCode() { return e.hashCode(); }
+ public String toString() { return e.toString(); }
+
+ public V setValue(V value) {
+ if (value != null && !valueType.isInstance(value))
+ throw new ClassCastException(badValueMsg(value));
+ return e.setValue(value);
+ }
+
+ private String badValueMsg(Object value) {
+ return "Attempt to insert " + value.getClass() +
+ " value into map with value type " + valueType;
+ }
+
+ public boolean equals(Object o) {
+ if (o == this)
+ return true;
+ if (!(o instanceof Map.Entry))
+ return false;
+ return e.equals(new AbstractMap.SimpleImmutableEntry
+ <Object, Object>((Map.Entry<?,?>)o));
+ }
+ }
+ }
+ }
+
+ /**
+ * Returns a dynamically typesafe view of the specified sorted map.
+ * Any attempt to insert a mapping whose key or value have the wrong
+ * type will result in an immediate {@link ClassCastException}.
+ * Similarly, any attempt to modify the value currently associated with
+ * a key will result in an immediate {@link ClassCastException},
+ * whether the modification is attempted directly through the map
+ * itself, or through a {@link Map.Entry} instance obtained from the
+ * map's {@link Map#entrySet() entry set} view.
+ *
+ * <p>Assuming a map contains no incorrectly typed keys or values
+ * prior to the time a dynamically typesafe view is generated, and
+ * that all subsequent access to the map takes place through the view
+ * (or one of its collection views), it is <i>guaranteed</i> that the
+ * map cannot contain an incorrectly typed key or value.
+ *
+ * <p>A discussion of the use of dynamically typesafe views may be
+ * found in the documentation for the {@link #checkedCollection
+ * checkedCollection} method.
+ *
+ * <p>The returned map will be serializable if the specified map is
+ * serializable.
+ *
+ * <p>Since {@code null} is considered to be a value of any reference
+ * type, the returned map permits insertion of null keys or values
+ * whenever the backing map does.
+ *
+ * @param m the map for which a dynamically typesafe view is to be
+ * returned
+ * @param keyType the type of key that {@code m} is permitted to hold
+ * @param valueType the type of value that {@code m} is permitted to hold
+ * @return a dynamically typesafe view of the specified map
+ * @since 1.5
+ */
+ public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m,
+ Class<K> keyType,
+ Class<V> valueType) {
+ return new CheckedSortedMap<K,V>(m, keyType, valueType);
+ }
+
+ /**
+ * @serial include
+ */
+ static class CheckedSortedMap<K,V> extends CheckedMap<K,V>
+ implements SortedMap<K,V>, Serializable
+ {
+ private static final long serialVersionUID = 1599671320688067438L;
+
+ private final SortedMap<K, V> sm;
+
+ CheckedSortedMap(SortedMap<K, V> m,
+ Class<K> keyType, Class<V> valueType) {
+ super(m, keyType, valueType);
+ sm = m;
+ }
+
+ public Comparator<? super K> comparator() { return sm.comparator(); }
+ public K firstKey() { return sm.firstKey(); }
+ public K lastKey() { return sm.lastKey(); }
+
+ public SortedMap<K,V> subMap(K fromKey, K toKey) {
+ return checkedSortedMap(sm.subMap(fromKey, toKey),
+ keyType, valueType);
+ }
+ public SortedMap<K,V> headMap(K toKey) {
+ return checkedSortedMap(sm.headMap(toKey), keyType, valueType);
+ }
+ public SortedMap<K,V> tailMap(K fromKey) {
+ return checkedSortedMap(sm.tailMap(fromKey), keyType, valueType);
+ }
+ }
+
+ // Empty collections
+
+ /**
+ * Returns an iterator that has no elements. More precisely,
+ *
+ * <ul compact>
+ *
+ * <li>{@link Iterator#hasNext hasNext} always returns {@code
+ * false}.
+ *
+ * <li>{@link Iterator#next next} always throws {@link
+ * NoSuchElementException}.
+ *
+ * <li>{@link Iterator#remove remove} always throws {@link
+ * IllegalStateException}.
+ *
+ * </ul>
+ *
+ * <p>Implementations of this method are permitted, but not
+ * required, to return the same object from multiple invocations.
+ *
+ * @return an empty iterator
+ * @since 1.7
+ */
+ @SuppressWarnings("unchecked")
+ public static <T> Iterator<T> emptyIterator() {
+ return (Iterator<T>) EmptyIterator.EMPTY_ITERATOR;
+ }
+
+ private static class EmptyIterator<E> implements Iterator<E> {
+ static final EmptyIterator<Object> EMPTY_ITERATOR
+ = new EmptyIterator<Object>();
+
+ public boolean hasNext() { return false; }
+ public E next() { throw new NoSuchElementException(); }
+ public void remove() { throw new IllegalStateException(); }
+ }
+
+ /**
+ * Returns a list iterator that has no elements. More precisely,
+ *
+ * <ul compact>
+ *
+ * <li>{@link Iterator#hasNext hasNext} and {@link
+ * ListIterator#hasPrevious hasPrevious} always return {@code
+ * false}.
+ *
+ * <li>{@link Iterator#next next} and {@link ListIterator#previous
+ * previous} always throw {@link NoSuchElementException}.
+ *
+ * <li>{@link Iterator#remove remove} and {@link ListIterator#set
+ * set} always throw {@link IllegalStateException}.
+ *
+ * <li>{@link ListIterator#add add} always throws {@link
+ * UnsupportedOperationException}.
+ *
+ * <li>{@link ListIterator#nextIndex nextIndex} always returns
+ * {@code 0} .
+ *
+ * <li>{@link ListIterator#previousIndex previousIndex} always
+ * returns {@code -1}.
+ *
+ * </ul>
+ *
+ * <p>Implementations of this method are permitted, but not
+ * required, to return the same object from multiple invocations.
+ *
+ * @return an empty list iterator
+ * @since 1.7
+ */
+ @SuppressWarnings("unchecked")
+ public static <T> ListIterator<T> emptyListIterator() {
+ return (ListIterator<T>) EmptyListIterator.EMPTY_ITERATOR;
+ }
+
+ private static class EmptyListIterator<E>
+ extends EmptyIterator<E>
+ implements ListIterator<E>
+ {
+ static final EmptyListIterator<Object> EMPTY_ITERATOR
+ = new EmptyListIterator<Object>();
+
+ public boolean hasPrevious() { return false; }
+ public E previous() { throw new NoSuchElementException(); }
+ public int nextIndex() { return 0; }
+ public int previousIndex() { return -1; }
+ public void set(E e) { throw new IllegalStateException(); }
+ public void add(E e) { throw new UnsupportedOperationException(); }
+ }
+
+ /**
+ * Returns an enumeration that has no elements. More precisely,
+ *
+ * <ul compact>
+ *
+ * <li>{@link Enumeration#hasMoreElements hasMoreElements} always
+ * returns {@code false}.
+ *
+ * <li> {@link Enumeration#nextElement nextElement} always throws
+ * {@link NoSuchElementException}.
+ *
+ * </ul>
+ *
+ * <p>Implementations of this method are permitted, but not
+ * required, to return the same object from multiple invocations.
+ *
+ * @return an empty enumeration
+ * @since 1.7
+ */
+ @SuppressWarnings("unchecked")
+ public static <T> Enumeration<T> emptyEnumeration() {
+ return (Enumeration<T>) EmptyEnumeration.EMPTY_ENUMERATION;
+ }
+
+ private static class EmptyEnumeration<E> implements Enumeration<E> {
+ static final EmptyEnumeration<Object> EMPTY_ENUMERATION
+ = new EmptyEnumeration<Object>();
+
+ public boolean hasMoreElements() { return false; }
+ public E nextElement() { throw new NoSuchElementException(); }
+ }
+
+ /**
+ * The empty set (immutable). This set is serializable.
+ *
+ * @see #emptySet()
+ */
+ @SuppressWarnings("unchecked")
+ public static final Set EMPTY_SET = new EmptySet<Object>();
+
+ /**
+ * Returns the empty set (immutable). This set is serializable.
+ * Unlike the like-named field, this method is parameterized.
+ *
+ * <p>This example illustrates the type-safe way to obtain an empty set:
+ * <pre>
+ * Set<String> s = Collections.emptySet();
+ * </pre>
+ * Implementation note: Implementations of this method need not
+ * create a separate <tt>Set</tt> object for each call. Using this
+ * method is likely to have comparable cost to using the like-named
+ * field. (Unlike this method, the field does not provide type safety.)
+ *
+ * @see #EMPTY_SET
+ * @since 1.5
+ */
+ @SuppressWarnings("unchecked")
+ public static final <T> Set<T> emptySet() {
+ return (Set<T>) EMPTY_SET;
+ }
+
+ /**
+ * @serial include
+ */
+ private static class EmptySet<E>
+ extends AbstractSet<E>
+ implements Serializable
+ {
+ private static final long serialVersionUID = 1582296315990362920L;
+
+ public Iterator<E> iterator() { return emptyIterator(); }
+
+ public int size() {return 0;}
+ public boolean isEmpty() {return true;}
+
+ public boolean contains(Object obj) {return false;}
+ public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
+
+ public Object[] toArray() { return new Object[0]; }
+
+ public <T> T[] toArray(T[] a) {
+ if (a.length > 0)
+ a[0] = null;
+ return a;
+ }
+
+ // Preserves singleton property
+ private Object readResolve() {
+ return EMPTY_SET;
+ }
+ }
+
+ /**
+ * The empty list (immutable). This list is serializable.
+ *
+ * @see #emptyList()
+ */
+ @SuppressWarnings("unchecked")
+ public static final List EMPTY_LIST = new EmptyList<Object>();
+
+ /**
+ * Returns the empty list (immutable). This list is serializable.
+ *
+ * <p>This example illustrates the type-safe way to obtain an empty list:
+ * <pre>
+ * List<String> s = Collections.emptyList();
+ * </pre>
+ * Implementation note: Implementations of this method need not
+ * create a separate <tt>List</tt> object for each call. Using this
+ * method is likely to have comparable cost to using the like-named
+ * field. (Unlike this method, the field does not provide type safety.)
+ *
+ * @see #EMPTY_LIST
+ * @since 1.5
+ */
+ @SuppressWarnings("unchecked")
+ public static final <T> List<T> emptyList() {
+ return (List<T>) EMPTY_LIST;
+ }
+
+ /**
+ * @serial include
+ */
+ private static class EmptyList<E>
+ extends AbstractList<E>
+ implements RandomAccess, Serializable {
+ private static final long serialVersionUID = 8842843931221139166L;
+
+ public Iterator<E> iterator() {
+ return emptyIterator();
+ }
+ public ListIterator<E> listIterator() {
+ return emptyListIterator();
+ }
+
+ public int size() {return 0;}
+ public boolean isEmpty() {return true;}
+
+ public boolean contains(Object obj) {return false;}
+ public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
+
+ public Object[] toArray() { return new Object[0]; }
+
+ public <T> T[] toArray(T[] a) {
+ if (a.length > 0)
+ a[0] = null;
+ return a;
+ }
+
+ public E get(int index) {
+ throw new IndexOutOfBoundsException("Index: "+index);
+ }
+
+ public boolean equals(Object o) {
+ return (o instanceof List) && ((List<?>)o).isEmpty();
+ }
+
+ public int hashCode() { return 1; }
+
+ // Preserves singleton property
+ private Object readResolve() {
+ return EMPTY_LIST;
+ }
+ }
+
+ /**
+ * The empty map (immutable). This map is serializable.
+ *
+ * @see #emptyMap()
+ * @since 1.3
+ */
+ @SuppressWarnings("unchecked")
+ public static final Map EMPTY_MAP = new EmptyMap<Object,Object>();
+
+ /**
+ * Returns the empty map (immutable). This map is serializable.
+ *
+ * <p>This example illustrates the type-safe way to obtain an empty set:
+ * <pre>
+ * Map<String, Date> s = Collections.emptyMap();
+ * </pre>
+ * Implementation note: Implementations of this method need not
+ * create a separate <tt>Map</tt> object for each call. Using this
+ * method is likely to have comparable cost to using the like-named
+ * field. (Unlike this method, the field does not provide type safety.)
+ *
+ * @see #EMPTY_MAP
+ * @since 1.5
+ */
+ @SuppressWarnings("unchecked")
+ public static final <K,V> Map<K,V> emptyMap() {
+ return (Map<K,V>) EMPTY_MAP;
+ }
+
+ /**
+ * @serial include
+ */
+ private static class EmptyMap<K,V>
+ extends AbstractMap<K,V>
+ implements Serializable
+ {
+ private static final long serialVersionUID = 6428348081105594320L;
+
+ public int size() {return 0;}
+ public boolean isEmpty() {return true;}
+ public boolean containsKey(Object key) {return false;}
+ public boolean containsValue(Object value) {return false;}
+ public V get(Object key) {return null;}
+ public Set<K> keySet() {return emptySet();}
+ public Collection<V> values() {return emptySet();}
+ public Set<Map.Entry<K,V>> entrySet() {return emptySet();}
+
+ public boolean equals(Object o) {
+ return (o instanceof Map) && ((Map<?,?>)o).isEmpty();
+ }
+
+ public int hashCode() {return 0;}
+
+ // Preserves singleton property
+ private Object readResolve() {
+ return EMPTY_MAP;
+ }
+ }
+
+ // Singleton collections
+
+ /**
+ * Returns an immutable set containing only the specified object.
+ * The returned set is serializable.
+ *
+ * @param o the sole object to be stored in the returned set.
+ * @return an immutable set containing only the specified object.
+ */
+ public static <T> Set<T> singleton(T o) {
+ return new SingletonSet<T>(o);
+ }
+
+ static <E> Iterator<E> singletonIterator(final E e) {
+ return new Iterator<E>() {
+ private boolean hasNext = true;
+ public boolean hasNext() {
+ return hasNext;
+ }
+ public E next() {
+ if (hasNext) {
+ hasNext = false;
+ return e;
+ }
+ throw new NoSuchElementException();
+ }
+ public void remove() {
+ throw new UnsupportedOperationException();
+ }
+ };
+ }
+
+ /**
+ * @serial include
+ */
+ private static class SingletonSet<E>
+ extends AbstractSet<E>
+ implements Serializable
+ {
+ private static final long serialVersionUID = 3193687207550431679L;
+
+ final private E element;
+
+ SingletonSet(E e) {element = e;}
+
+ public Iterator<E> iterator() {
+ return singletonIterator(element);
+ }
+
+ public int size() {return 1;}
+
+ public boolean contains(Object o) {return eq(o, element);}
+ }
+
+ /**
+ * Returns an immutable list containing only the specified object.
+ * The returned list is serializable.
+ *
+ * @param o the sole object to be stored in the returned list.
+ * @return an immutable list containing only the specified object.
+ * @since 1.3
+ */
+ public static <T> List<T> singletonList(T o) {
+ return new SingletonList<T>(o);
+ }
+
+ /**
+ * @serial include
+ */
+ private static class SingletonList<E>
+ extends AbstractList<E>
+ implements RandomAccess, Serializable {
+
+ private static final long serialVersionUID = 3093736618740652951L;
+
+ private final E element;
+
+ SingletonList(E obj) {element = obj;}
+
+ public Iterator<E> iterator() {
+ return singletonIterator(element);
+ }
+
+ public int size() {return 1;}
+
+ public boolean contains(Object obj) {return eq(obj, element);}
+
+ public E get(int index) {
+ if (index != 0)
+ throw new IndexOutOfBoundsException("Index: "+index+", Size: 1");
+ return element;
+ }
+ }
+
+ /**
+ * Returns an immutable map, mapping only the specified key to the
+ * specified value. The returned map is serializable.
+ *
+ * @param key the sole key to be stored in the returned map.
+ * @param value the value to which the returned map maps <tt>key</tt>.
+ * @return an immutable map containing only the specified key-value
+ * mapping.
+ * @since 1.3
+ */
+ public static <K,V> Map<K,V> singletonMap(K key, V value) {
+ return new SingletonMap<K,V>(key, value);
+ }
+
+ /**
+ * @serial include
+ */
+ private static class SingletonMap<K,V>
+ extends AbstractMap<K,V>
+ implements Serializable {
+ private static final long serialVersionUID = -6979724477215052911L;
+
+ private final K k;
+ private final V v;
+
+ SingletonMap(K key, V value) {
+ k = key;
+ v = value;
+ }
+
+ public int size() {return 1;}
+
+ public boolean isEmpty() {return false;}
+
+ public boolean containsKey(Object key) {return eq(key, k);}
+
+ public boolean containsValue(Object value) {return eq(value, v);}
+
+ public V get(Object key) {return (eq(key, k) ? v : null);}
+
+ private transient Set<K> keySet = null;
+ private transient Set<Map.Entry<K,V>> entrySet = null;
+ private transient Collection<V> values = null;
+
+ public Set<K> keySet() {
+ if (keySet==null)
+ keySet = singleton(k);
+ return keySet;
+ }
+
+ public Set<Map.Entry<K,V>> entrySet() {
+ if (entrySet==null)
+ entrySet = Collections.<Map.Entry<K,V>>singleton(
+ new SimpleImmutableEntry<K,V>(k, v));
+ return entrySet;
+ }
+
+ public Collection<V> values() {
+ if (values==null)
+ values = singleton(v);
+ return values;
+ }
+
+ }
+
+ // Miscellaneous
+
+ /**
+ * Returns an immutable list consisting of <tt>n</tt> copies of the
+ * specified object. The newly allocated data object is tiny (it contains
+ * a single reference to the data object). This method is useful in
+ * combination with the <tt>List.addAll</tt> method to grow lists.
+ * The returned list is serializable.
+ *
+ * @param n the number of elements in the returned list.
+ * @param o the element to appear repeatedly in the returned list.
+ * @return an immutable list consisting of <tt>n</tt> copies of the
+ * specified object.
+ * @throws IllegalArgumentException if n < 0.
+ * @see List#addAll(Collection)
+ * @see List#addAll(int, Collection)
+ */
+ public static <T> List<T> nCopies(int n, T o) {
+ if (n < 0)
+ throw new IllegalArgumentException("List length = " + n);
+ return new CopiesList<T>(n, o);
+ }
+
+ /**
+ * @serial include
+ */
+ private static class CopiesList<E>
+ extends AbstractList<E>
+ implements RandomAccess, Serializable
+ {
+ private static final long serialVersionUID = 2739099268398711800L;
+
+ final int n;
+ final E element;
+
+ CopiesList(int n, E e) {
+ assert n >= 0;
+ this.n = n;
+ element = e;
+ }
+
+ public int size() {
+ return n;
+ }
+
+ public boolean contains(Object obj) {
+ return n != 0 && eq(obj, element);
+ }
+
+ public int indexOf(Object o) {
+ return contains(o) ? 0 : -1;
+ }
+
+ public int lastIndexOf(Object o) {
+ return contains(o) ? n - 1 : -1;
+ }
+
+ public E get(int index) {
+ if (index < 0 || index >= n)
+ throw new IndexOutOfBoundsException("Index: "+index+
+ ", Size: "+n);
+ return element;
+ }
+
+ public Object[] toArray() {
+ final Object[] a = new Object[n];
+ if (element != null)
+ Arrays.fill(a, 0, n, element);
+ return a;
+ }
+
+ public <T> T[] toArray(T[] a) {
+ final int n = this.n;
+ if (a.length < n) {
+ a = (T[])java.lang.reflect.Array
+ .newInstance(a.getClass().getComponentType(), n);
+ if (element != null)
+ Arrays.fill(a, 0, n, element);
+ } else {
+ Arrays.fill(a, 0, n, element);
+ if (a.length > n)
+ a[n] = null;
+ }
+ return a;
+ }
+
+ public List<E> subList(int fromIndex, int toIndex) {
+ if (fromIndex < 0)
+ throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
+ if (toIndex > n)
+ throw new IndexOutOfBoundsException("toIndex = " + toIndex);
+ if (fromIndex > toIndex)
+ throw new IllegalArgumentException("fromIndex(" + fromIndex +
+ ") > toIndex(" + toIndex + ")");
+ return new CopiesList<E>(toIndex - fromIndex, element);
+ }
+ }
+
+ /**
+ * Returns a comparator that imposes the reverse of the <i>natural
+ * ordering</i> on a collection of objects that implement the
+ * <tt>Comparable</tt> interface. (The natural ordering is the ordering
+ * imposed by the objects' own <tt>compareTo</tt> method.) This enables a
+ * simple idiom for sorting (or maintaining) collections (or arrays) of
+ * objects that implement the <tt>Comparable</tt> interface in
+ * reverse-natural-order. For example, suppose a is an array of
+ * strings. Then: <pre>
+ * Arrays.sort(a, Collections.reverseOrder());
+ * </pre> sorts the array in reverse-lexicographic (alphabetical) order.<p>
+ *
+ * The returned comparator is serializable.
+ *
+ * @return a comparator that imposes the reverse of the <i>natural
+ * ordering</i> on a collection of objects that implement
+ * the <tt>Comparable</tt> interface.
+ * @see Comparable
+ */
+ public static <T> Comparator<T> reverseOrder() {
+ return (Comparator<T>) ReverseComparator.REVERSE_ORDER;
+ }
+
+ /**
+ * @serial include
+ */
+ private static class ReverseComparator
+ implements Comparator<Comparable<Object>>, Serializable {
+
+ private static final long serialVersionUID = 7207038068494060240L;
+
+ static final ReverseComparator REVERSE_ORDER
+ = new ReverseComparator();
+
+ public int compare(Comparable<Object> c1, Comparable<Object> c2) {
+ return c2.compareTo(c1);
+ }
+
+ private Object readResolve() { return reverseOrder(); }
+ }
+
+ /**
+ * Returns a comparator that imposes the reverse ordering of the specified
+ * comparator. If the specified comparator is null, this method is
+ * equivalent to {@link #reverseOrder()} (in other words, it returns a
+ * comparator that imposes the reverse of the <i>natural ordering</i> on a
+ * collection of objects that implement the Comparable interface).
+ *
+ * <p>The returned comparator is serializable (assuming the specified
+ * comparator is also serializable or null).
+ *
+ * @return a comparator that imposes the reverse ordering of the
+ * specified comparator
+ * @since 1.5
+ */
+ public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) {
+ if (cmp == null)
+ return reverseOrder();
+
+ if (cmp instanceof ReverseComparator2)
+ return ((ReverseComparator2<T>)cmp).cmp;
+
+ return new ReverseComparator2<T>(cmp);
+ }
+
+ /**
+ * @serial include
+ */
+ private static class ReverseComparator2<T> implements Comparator<T>,
+ Serializable
+ {
+ private static final long serialVersionUID = 4374092139857L;
+
+ /**
+ * The comparator specified in the static factory. This will never
+ * be null, as the static factory returns a ReverseComparator
+ * instance if its argument is null.
+ *
+ * @serial
+ */
+ final Comparator<T> cmp;
+
+ ReverseComparator2(Comparator<T> cmp) {
+ assert cmp != null;
+ this.cmp = cmp;
+ }
+
+ public int compare(T t1, T t2) {
+ return cmp.compare(t2, t1);
+ }
+
+ public boolean equals(Object o) {
+ return (o == this) ||
+ (o instanceof ReverseComparator2 &&
+ cmp.equals(((ReverseComparator2)o).cmp));
+ }
+
+ public int hashCode() {
+ return cmp.hashCode() ^ Integer.MIN_VALUE;
+ }
+ }
+
+ /**
+ * Returns an enumeration over the specified collection. This provides
+ * interoperability with legacy APIs that require an enumeration
+ * as input.
+ *
+ * @param c the collection for which an enumeration is to be returned.
+ * @return an enumeration over the specified collection.
+ * @see Enumeration
+ */
+ public static <T> Enumeration<T> enumeration(final Collection<T> c) {
+ return new Enumeration<T>() {
+ private final Iterator<T> i = c.iterator();
+
+ public boolean hasMoreElements() {
+ return i.hasNext();
+ }
+
+ public T nextElement() {
+ return i.next();
+ }
+ };
+ }
+
+ /**
+ * Returns an array list containing the elements returned by the
+ * specified enumeration in the order they are returned by the
+ * enumeration. This method provides interoperability between
+ * legacy APIs that return enumerations and new APIs that require
+ * collections.
+ *
+ * @param e enumeration providing elements for the returned
+ * array list
+ * @return an array list containing the elements returned
+ * by the specified enumeration.
+ * @since 1.4
+ * @see Enumeration
+ * @see ArrayList
+ */
+ public static <T> ArrayList<T> list(Enumeration<T> e) {
+ ArrayList<T> l = new ArrayList<T>();
+ while (e.hasMoreElements())
+ l.add(e.nextElement());
+ return l;
+ }
+
+ /**
+ * Returns true if the specified arguments are equal, or both null.
+ */
+ static boolean eq(Object o1, Object o2) {
+ return o1==null ? o2==null : o1.equals(o2);
+ }
+
+ /**
+ * Returns the number of elements in the specified collection equal to the
+ * specified object. More formally, returns the number of elements
+ * <tt>e</tt> in the collection such that
+ * <tt>(o == null ? e == null : o.equals(e))</tt>.
+ *
+ * @param c the collection in which to determine the frequency
+ * of <tt>o</tt>
+ * @param o the object whose frequency is to be determined
+ * @throws NullPointerException if <tt>c</tt> is null
+ * @since 1.5
+ */
+ public static int frequency(Collection<?> c, Object o) {
+ int result = 0;
+ if (o == null) {
+ for (Object e : c)
+ if (e == null)
+ result++;
+ } else {
+ for (Object e : c)
+ if (o.equals(e))
+ result++;
+ }
+ return result;
+ }
+
+ /**
+ * Returns <tt>true</tt> if the two specified collections have no
+ * elements in common.
+ *
+ * <p>Care must be exercised if this method is used on collections that
+ * do not comply with the general contract for <tt>Collection</tt>.
+ * Implementations may elect to iterate over either collection and test
+ * for containment in the other collection (or to perform any equivalent
+ * computation). If either collection uses a nonstandard equality test
+ * (as does a {@link SortedSet} whose ordering is not <i>compatible with
+ * equals</i>, or the key set of an {@link IdentityHashMap}), both
+ * collections must use the same nonstandard equality test, or the
+ * result of this method is undefined.
+ *
+ * <p>Note that it is permissible to pass the same collection in both
+ * parameters, in which case the method will return true if and only if
+ * the collection is empty.
+ *
+ * @param c1 a collection
+ * @param c2 a collection
+ * @throws NullPointerException if either collection is null
+ * @since 1.5
+ */
+ public static boolean disjoint(Collection<?> c1, Collection<?> c2) {
+ /*
+ * We're going to iterate through c1 and test for inclusion in c2.
+ * If c1 is a Set and c2 isn't, swap the collections. Otherwise,
+ * place the shorter collection in c1. Hopefully this heuristic
+ * will minimize the cost of the operation.
+ */
+ if ((c1 instanceof Set) && !(c2 instanceof Set) ||
+ (c1.size() > c2.size())) {
+ Collection<?> tmp = c1;
+ c1 = c2;
+ c2 = tmp;
+ }
+
+ for (Object e : c1)
+ if (c2.contains(e))
+ return false;
+ return true;
+ }
+
+ /**
+ * Adds all of the specified elements to the specified collection.
+ * Elements to be added may be specified individually or as an array.
+ * The behavior of this convenience method is identical to that of
+ * <tt>c.addAll(Arrays.asList(elements))</tt>, but this method is likely
+ * to run significantly faster under most implementations.
+ *
+ * <p>When elements are specified individually, this method provides a
+ * convenient way to add a few elements to an existing collection:
+ * <pre>
+ * Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon");
+ * </pre>
+ *
+ * @param c the collection into which <tt>elements</tt> are to be inserted
+ * @param elements the elements to insert into <tt>c</tt>
+ * @return <tt>true</tt> if the collection changed as a result of the call
+ * @throws UnsupportedOperationException if <tt>c</tt> does not support
+ * the <tt>add</tt> operation
+ * @throws NullPointerException if <tt>elements</tt> contains one or more
+ * null values and <tt>c</tt> does not permit null elements, or
+ * if <tt>c</tt> or <tt>elements</tt> are <tt>null</tt>
+ * @throws IllegalArgumentException if some property of a value in
+ * <tt>elements</tt> prevents it from being added to <tt>c</tt>
+ * @see Collection#addAll(Collection)
+ * @since 1.5
+ */
+ public static <T> boolean addAll(Collection<? super T> c, T... elements) {
+ boolean result = false;
+ for (T element : elements)
+ result |= c.add(element);
+ return result;
+ }
+
+ /**
+ * Returns a set backed by the specified map. The resulting set displays
+ * the same ordering, concurrency, and performance characteristics as the
+ * backing map. In essence, this factory method provides a {@link Set}
+ * implementation corresponding to any {@link Map} implementation. There
+ * is no need to use this method on a {@link Map} implementation that
+ * already has a corresponding {@link Set} implementation (such as {@link
+ * HashMap} or {@link TreeMap}).
+ *
+ * <p>Each method invocation on the set returned by this method results in
+ * exactly one method invocation on the backing map or its <tt>keySet</tt>
+ * view, with one exception. The <tt>addAll</tt> method is implemented
+ * as a sequence of <tt>put</tt> invocations on the backing map.
+ *
+ * <p>The specified map must be empty at the time this method is invoked,
+ * and should not be accessed directly after this method returns. These
+ * conditions are ensured if the map is created empty, passed directly
+ * to this method, and no reference to the map is retained, as illustrated
+ * in the following code fragment:
+ * <pre>
+ * Set<Object> weakHashSet = Collections.newSetFromMap(
+ * new WeakHashMap<Object, Boolean>());
+ * </pre>
+ *
+ * @param map the backing map
+ * @return the set backed by the map
+ * @throws IllegalArgumentException if <tt>map</tt> is not empty
+ * @since 1.6
+ */
+ public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) {
+ return new SetFromMap<E>(map);
+ }
+
+ /**
+ * @serial include
+ */
+ private static class SetFromMap<E> extends AbstractSet<E>
+ implements Set<E>, Serializable
+ {
+ private final Map<E, Boolean> m; // The backing map
+ private transient Set<E> s; // Its keySet
+
+ SetFromMap(Map<E, Boolean> map) {
+ if (!map.isEmpty())
+ throw new IllegalArgumentException("Map is non-empty");
+ m = map;
+ s = map.keySet();
+ }
+
+ public void clear() { m.clear(); }
+ public int size() { return m.size(); }
+ public boolean isEmpty() { return m.isEmpty(); }
+ public boolean contains(Object o) { return m.containsKey(o); }
+ public boolean remove(Object o) { return m.remove(o) != null; }
+ public boolean add(E e) { return m.put(e, Boolean.TRUE) == null; }
+ public Iterator<E> iterator() { return s.iterator(); }
+ public Object[] toArray() { return s.toArray(); }
+ public <T> T[] toArray(T[] a) { return s.toArray(a); }
+ public String toString() { return s.toString(); }
+ public int hashCode() { return s.hashCode(); }
+ public boolean equals(Object o) { return o == this || s.equals(o); }
+ public boolean containsAll(Collection<?> c) {return s.containsAll(c);}
+ public boolean removeAll(Collection<?> c) {return s.removeAll(c);}
+ public boolean retainAll(Collection<?> c) {return s.retainAll(c);}
+ // addAll is the only inherited implementation
+
+ private static final long serialVersionUID = 2454657854757543876L;
+
+ private void readObject(java.io.ObjectInputStream stream)
+ throws IOException, ClassNotFoundException
+ {
+ stream.defaultReadObject();
+ s = m.keySet();
+ }
+ }
+
+ /**
+ * Returns a view of a {@link Deque} as a Last-in-first-out (Lifo)
+ * {@link Queue}. Method <tt>add</tt> is mapped to <tt>push</tt>,
+ * <tt>remove</tt> is mapped to <tt>pop</tt> and so on. This
+ * view can be useful when you would like to use a method
+ * requiring a <tt>Queue</tt> but you need Lifo ordering.
+ *
+ * <p>Each method invocation on the queue returned by this method
+ * results in exactly one method invocation on the backing deque, with
+ * one exception. The {@link Queue#addAll addAll} method is
+ * implemented as a sequence of {@link Deque#addFirst addFirst}
+ * invocations on the backing deque.
+ *
+ * @param deque the deque
+ * @return the queue
+ * @since 1.6
+ */
+ public static <T> Queue<T> asLifoQueue(Deque<T> deque) {
+ return new AsLIFOQueue<T>(deque);
+ }
+
+ /**
+ * @serial include
+ */
+ static class AsLIFOQueue<E> extends AbstractQueue<E>
+ implements Queue<E>, Serializable {
+ private static final long serialVersionUID = 1802017725587941708L;
+ private final Deque<E> q;
+ AsLIFOQueue(Deque<E> q) { this.q = q; }
+ public boolean add(E e) { q.addFirst(e); return true; }
+ public boolean offer(E e) { return q.offerFirst(e); }
+ public E poll() { return q.pollFirst(); }
+ public E remove() { return q.removeFirst(); }
+ public E peek() { return q.peekFirst(); }
+ public E element() { return q.getFirst(); }
+ public void clear() { q.clear(); }
+ public int size() { return q.size(); }
+ public boolean isEmpty() { return q.isEmpty(); }
+ public boolean contains(Object o) { return q.contains(o); }
+ public boolean remove(Object o) { return q.remove(o); }
+ public Iterator<E> iterator() { return q.iterator(); }
+ public Object[] toArray() { return q.toArray(); }
+ public <T> T[] toArray(T[] a) { return q.toArray(a); }
+ public String toString() { return q.toString(); }
+ public boolean containsAll(Collection<?> c) {return q.containsAll(c);}
+ public boolean removeAll(Collection<?> c) {return q.removeAll(c);}
+ public boolean retainAll(Collection<?> c) {return q.retainAll(c);}
+ // We use inherited addAll; forwarding addAll would be wrong
+ }
+}