--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/util/HashSet.java Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,312 @@
+/*
+ * Copyright 1997-2006 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;
+
+/**
+ * This class implements the <tt>Set</tt> interface, backed by a hash table
+ * (actually a <tt>HashMap</tt> instance). It makes no guarantees as to the
+ * iteration order of the set; in particular, it does not guarantee that the
+ * order will remain constant over time. This class permits the <tt>null</tt>
+ * element.
+ *
+ * <p>This class offers constant time performance for the basic operations
+ * (<tt>add</tt>, <tt>remove</tt>, <tt>contains</tt> and <tt>size</tt>),
+ * assuming the hash function disperses the elements properly among the
+ * buckets. Iterating over this set requires time proportional to the sum of
+ * the <tt>HashSet</tt> instance's size (the number of elements) plus the
+ * "capacity" of the backing <tt>HashMap</tt> instance (the number of
+ * buckets). Thus, it's very important not to set the initial capacity too
+ * high (or the load factor too low) if iteration performance is important.
+ *
+ * <p><strong>Note that this implementation is not synchronized.</strong>
+ * If multiple threads access a hash set concurrently, and at least one of
+ * the threads modifies the set, it <i>must</i> be synchronized externally.
+ * This is typically accomplished by synchronizing on some object that
+ * naturally encapsulates the set.
+ *
+ * If no such object exists, the set should be "wrapped" using the
+ * {@link Collections#synchronizedSet Collections.synchronizedSet}
+ * method. This is best done at creation time, to prevent accidental
+ * unsynchronized access to the set:<pre>
+ * Set s = Collections.synchronizedSet(new HashSet(...));</pre>
+ *
+ * <p>The iterators returned by this class's <tt>iterator</tt> method are
+ * <i>fail-fast</i>: if the set is modified at any time after the iterator is
+ * created, in any way except through the iterator's own <tt>remove</tt>
+ * method, the Iterator throws a {@link ConcurrentModificationException}.
+ * Thus, in the face of concurrent modification, the iterator fails quickly
+ * and cleanly, rather than risking arbitrary, non-deterministic behavior at
+ * an undetermined time in the future.
+ *
+ * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
+ * as it is, generally speaking, impossible to make any hard guarantees in the
+ * presence of unsynchronized concurrent modification. Fail-fast iterators
+ * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
+ * Therefore, it would be wrong to write a program that depended on this
+ * exception for its correctness: <i>the fail-fast behavior of iterators
+ * should be used only to detect bugs.</i>
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/../technotes/guides/collections/index.html">
+ * Java Collections Framework</a>.
+ *
+ * @param <E> the type of elements maintained by this set
+ *
+ * @author Josh Bloch
+ * @author Neal Gafter
+ * @see Collection
+ * @see Set
+ * @see TreeSet
+ * @see HashMap
+ * @since 1.2
+ */
+
+public class HashSet<E>
+ extends AbstractSet<E>
+ implements Set<E>, Cloneable, java.io.Serializable
+{
+ static final long serialVersionUID = -5024744406713321676L;
+
+ private transient HashMap<E,Object> map;
+
+ // Dummy value to associate with an Object in the backing Map
+ private static final Object PRESENT = new Object();
+
+ /**
+ * Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
+ * default initial capacity (16) and load factor (0.75).
+ */
+ public HashSet() {
+ map = new HashMap<E,Object>();
+ }
+
+ /**
+ * Constructs a new set containing the elements in the specified
+ * collection. The <tt>HashMap</tt> is created with default load factor
+ * (0.75) and an initial capacity sufficient to contain the elements in
+ * the specified collection.
+ *
+ * @param c the collection whose elements are to be placed into this set
+ * @throws NullPointerException if the specified collection is null
+ */
+ public HashSet(Collection<? extends E> c) {
+ map = new HashMap<E,Object>(Math.max((int) (c.size()/.75f) + 1, 16));
+ addAll(c);
+ }
+
+ /**
+ * Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
+ * the specified initial capacity and the specified load factor.
+ *
+ * @param initialCapacity the initial capacity of the hash map
+ * @param loadFactor the load factor of the hash map
+ * @throws IllegalArgumentException if the initial capacity is less
+ * than zero, or if the load factor is nonpositive
+ */
+ public HashSet(int initialCapacity, float loadFactor) {
+ map = new HashMap<E,Object>(initialCapacity, loadFactor);
+ }
+
+ /**
+ * Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
+ * the specified initial capacity and default load factor (0.75).
+ *
+ * @param initialCapacity the initial capacity of the hash table
+ * @throws IllegalArgumentException if the initial capacity is less
+ * than zero
+ */
+ public HashSet(int initialCapacity) {
+ map = new HashMap<E,Object>(initialCapacity);
+ }
+
+ /**
+ * Constructs a new, empty linked hash set. (This package private
+ * constructor is only used by LinkedHashSet.) The backing
+ * HashMap instance is a LinkedHashMap with the specified initial
+ * capacity and the specified load factor.
+ *
+ * @param initialCapacity the initial capacity of the hash map
+ * @param loadFactor the load factor of the hash map
+ * @param dummy ignored (distinguishes this
+ * constructor from other int, float constructor.)
+ * @throws IllegalArgumentException if the initial capacity is less
+ * than zero, or if the load factor is nonpositive
+ */
+ HashSet(int initialCapacity, float loadFactor, boolean dummy) {
+ map = new LinkedHashMap<E,Object>(initialCapacity, loadFactor);
+ }
+
+ /**
+ * Returns an iterator over the elements in this set. The elements
+ * are returned in no particular order.
+ *
+ * @return an Iterator over the elements in this set
+ * @see ConcurrentModificationException
+ */
+ public Iterator<E> iterator() {
+ return map.keySet().iterator();
+ }
+
+ /**
+ * Returns the number of elements in this set (its cardinality).
+ *
+ * @return the number of elements in this set (its cardinality)
+ */
+ public int size() {
+ return map.size();
+ }
+
+ /**
+ * Returns <tt>true</tt> if this set contains no elements.
+ *
+ * @return <tt>true</tt> if this set contains no elements
+ */
+ public boolean isEmpty() {
+ return map.isEmpty();
+ }
+
+ /**
+ * Returns <tt>true</tt> if this set contains the specified element.
+ * More formally, returns <tt>true</tt> if and only if this set
+ * contains an element <tt>e</tt> such that
+ * <tt>(o==null ? e==null : o.equals(e))</tt>.
+ *
+ * @param o element whose presence in this set is to be tested
+ * @return <tt>true</tt> if this set contains the specified element
+ */
+ public boolean contains(Object o) {
+ return map.containsKey(o);
+ }
+
+ /**
+ * Adds the specified element to this set if it is not already present.
+ * More formally, adds the specified element <tt>e</tt> to this set if
+ * this set contains no element <tt>e2</tt> such that
+ * <tt>(e==null ? e2==null : e.equals(e2))</tt>.
+ * If this set already contains the element, the call leaves the set
+ * unchanged and returns <tt>false</tt>.
+ *
+ * @param e element to be added to this set
+ * @return <tt>true</tt> if this set did not already contain the specified
+ * element
+ */
+ public boolean add(E e) {
+ return map.put(e, PRESENT)==null;
+ }
+
+ /**
+ * Removes the specified element from this set if it is present.
+ * More formally, removes an element <tt>e</tt> such that
+ * <tt>(o==null ? e==null : o.equals(e))</tt>,
+ * if this set contains such an element. Returns <tt>true</tt> if
+ * this set contained the element (or equivalently, if this set
+ * changed as a result of the call). (This set will not contain the
+ * element once the call returns.)
+ *
+ * @param o object to be removed from this set, if present
+ * @return <tt>true</tt> if the set contained the specified element
+ */
+ public boolean remove(Object o) {
+ return map.remove(o)==PRESENT;
+ }
+
+ /**
+ * Removes all of the elements from this set.
+ * The set will be empty after this call returns.
+ */
+ public void clear() {
+ map.clear();
+ }
+
+ /**
+ * Returns a shallow copy of this <tt>HashSet</tt> instance: the elements
+ * themselves are not cloned.
+ *
+ * @return a shallow copy of this set
+ */
+ public Object clone() {
+ try {
+ HashSet<E> newSet = (HashSet<E>) super.clone();
+ newSet.map = (HashMap<E, Object>) map.clone();
+ return newSet;
+ } catch (CloneNotSupportedException e) {
+ throw new InternalError();
+ }
+ }
+
+ /**
+ * Save the state of this <tt>HashSet</tt> instance to a stream (that is,
+ * serialize it).
+ *
+ * @serialData The capacity of the backing <tt>HashMap</tt> instance
+ * (int), and its load factor (float) are emitted, followed by
+ * the size of the set (the number of elements it contains)
+ * (int), followed by all of its elements (each an Object) in
+ * no particular order.
+ */
+ private void writeObject(java.io.ObjectOutputStream s)
+ throws java.io.IOException {
+ // Write out any hidden serialization magic
+ s.defaultWriteObject();
+
+ // Write out HashMap capacity and load factor
+ s.writeInt(map.capacity());
+ s.writeFloat(map.loadFactor());
+
+ // Write out size
+ s.writeInt(map.size());
+
+ // Write out all elements in the proper order.
+ for (Iterator i=map.keySet().iterator(); i.hasNext(); )
+ s.writeObject(i.next());
+ }
+
+ /**
+ * Reconstitute the <tt>HashSet</tt> instance from a stream (that is,
+ * deserialize it).
+ */
+ private void readObject(java.io.ObjectInputStream s)
+ throws java.io.IOException, ClassNotFoundException {
+ // Read in any hidden serialization magic
+ s.defaultReadObject();
+
+ // Read in HashMap capacity and load factor and create backing HashMap
+ int capacity = s.readInt();
+ float loadFactor = s.readFloat();
+ map = (((HashSet)this) instanceof LinkedHashSet ?
+ new LinkedHashMap<E,Object>(capacity, loadFactor) :
+ new HashMap<E,Object>(capacity, loadFactor));
+
+ // Read in size
+ int size = s.readInt();
+
+ // Read in all elements in the proper order.
+ for (int i=0; i<size; i++) {
+ E e = (E) s.readObject();
+ map.put(e, PRESENT);
+ }
+ }
+}