--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/util/Collection.java Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,440 @@
+/*
+ * 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;
+
+/**
+ * The root interface in the <i>collection hierarchy</i>. A collection
+ * represents a group of objects, known as its <i>elements</i>. Some
+ * collections allow duplicate elements and others do not. Some are ordered
+ * and others unordered. The JDK does not provide any <i>direct</i>
+ * implementations of this interface: it provides implementations of more
+ * specific subinterfaces like <tt>Set</tt> and <tt>List</tt>. This interface
+ * is typically used to pass collections around and manipulate them where
+ * maximum generality is desired.
+ *
+ * <p><i>Bags</i> or <i>multisets</i> (unordered collections that may contain
+ * duplicate elements) should implement this interface directly.
+ *
+ * <p>All general-purpose <tt>Collection</tt> implementation classes (which
+ * typically implement <tt>Collection</tt> indirectly through one of its
+ * subinterfaces) should provide two "standard" constructors: a void (no
+ * arguments) constructor, which creates an empty collection, and a
+ * constructor with a single argument of type <tt>Collection</tt>, which
+ * creates a new collection with the same elements as its argument. In
+ * effect, the latter constructor allows the user to copy any collection,
+ * producing an equivalent collection of the desired implementation type.
+ * There is no way to enforce this convention (as interfaces cannot contain
+ * constructors) but all of the general-purpose <tt>Collection</tt>
+ * implementations in the Java platform libraries comply.
+ *
+ * <p>The "destructive" methods contained in this interface, that is, the
+ * methods that modify the collection on which they operate, are specified to
+ * throw <tt>UnsupportedOperationException</tt> if this collection does not
+ * support the operation. If this is the case, these methods may, but are not
+ * required to, throw an <tt>UnsupportedOperationException</tt> if the
+ * invocation would have no effect on the collection. For example, invoking
+ * the {@link #addAll(Collection)} method on an unmodifiable collection may,
+ * but is not required to, throw the exception if the collection to be added
+ * is empty.
+ *
+ * <p>Some collection implementations have restrictions on the elements that
+ * they may contain. For example, some implementations prohibit null elements,
+ * and some have restrictions on the types of their elements. Attempting to
+ * add an ineligible element throws an unchecked exception, typically
+ * <tt>NullPointerException</tt> or <tt>ClassCastException</tt>. Attempting
+ * to query the presence of an ineligible element may throw an exception,
+ * or it may simply return false; some implementations will exhibit the former
+ * behavior and some will exhibit the latter. More generally, attempting an
+ * operation on an ineligible element whose completion would not result in
+ * the insertion of an ineligible element into the collection may throw an
+ * exception or it may succeed, at the option of the implementation.
+ * Such exceptions are marked as "optional" in the specification for this
+ * interface.
+ *
+ * <p>It is up to each collection to determine its own synchronization
+ * policy. In the absence of a stronger guarantee by the
+ * implementation, undefined behavior may result from the invocation
+ * of any method on a collection that is being mutated by another
+ * thread; this includes direct invocations, passing the collection to
+ * a method that might perform invocations, and using an existing
+ * iterator to examine the collection.
+ *
+ * <p>Many methods in Collections Framework interfaces are defined in
+ * terms of the {@link Object#equals(Object) equals} method. For example,
+ * the specification for the {@link #contains(Object) contains(Object o)}
+ * method says: "returns <tt>true</tt> if and only if this collection
+ * contains at least one element <tt>e</tt> such that
+ * <tt>(o==null ? e==null : o.equals(e))</tt>." This specification should
+ * <i>not</i> be construed to imply that invoking <tt>Collection.contains</tt>
+ * with a non-null argument <tt>o</tt> will cause <tt>o.equals(e)</tt> to be
+ * invoked for any element <tt>e</tt>. Implementations are free to implement
+ * optimizations whereby the <tt>equals</tt> invocation is avoided, for
+ * example, by first comparing the hash codes of the two elements. (The
+ * {@link Object#hashCode()} specification guarantees that two objects with
+ * unequal hash codes cannot be equal.) More generally, implementations of
+ * the various Collections Framework interfaces are free to take advantage of
+ * the specified behavior of underlying {@link Object} methods wherever the
+ * implementor deems it appropriate.
+ *
+ * <p>This interface is a member of the
+ * <a href="{@docRoot}/../technotes/guides/collections/index.html">
+ * Java Collections Framework</a>.
+ *
+ * @author Josh Bloch
+ * @author Neal Gafter
+ * @see Set
+ * @see List
+ * @see Map
+ * @see SortedSet
+ * @see SortedMap
+ * @see HashSet
+ * @see TreeSet
+ * @see ArrayList
+ * @see LinkedList
+ * @see Vector
+ * @see Collections
+ * @see Arrays
+ * @see AbstractCollection
+ * @since 1.2
+ */
+
+public interface Collection<E> extends Iterable<E> {
+ // Query Operations
+
+ /**
+ * Returns the number of elements in this collection. If this collection
+ * contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
+ * <tt>Integer.MAX_VALUE</tt>.
+ *
+ * @return the number of elements in this collection
+ */
+ int size();
+
+ /**
+ * Returns <tt>true</tt> if this collection contains no elements.
+ *
+ * @return <tt>true</tt> if this collection contains no elements
+ */
+ boolean isEmpty();
+
+ /**
+ * Returns <tt>true</tt> if this collection contains the specified element.
+ * More formally, returns <tt>true</tt> if and only if this collection
+ * contains at least one element <tt>e</tt> such that
+ * <tt>(o==null ? e==null : o.equals(e))</tt>.
+ *
+ * @param o element whose presence in this collection is to be tested
+ * @return <tt>true</tt> if this collection contains the specified
+ * element
+ * @throws ClassCastException if the type of the specified element
+ * is incompatible with this collection (optional)
+ * @throws NullPointerException if the specified element is null and this
+ * collection does not permit null elements (optional)
+ */
+ boolean contains(Object o);
+
+ /**
+ * Returns an iterator over the elements in this collection. There are no
+ * guarantees concerning the order in which the elements are returned
+ * (unless this collection is an instance of some class that provides a
+ * guarantee).
+ *
+ * @return an <tt>Iterator</tt> over the elements in this collection
+ */
+ Iterator<E> iterator();
+
+ /**
+ * Returns an array containing all of the elements in this collection.
+ * If this collection makes any guarantees as to what order its elements
+ * are returned by its iterator, this method must return the elements in
+ * the same order.
+ *
+ * <p>The returned array will be "safe" in that no references to it are
+ * maintained by this collection. (In other words, this method must
+ * allocate a new array even if this collection is backed by an array).
+ * The caller is thus free to modify the returned array.
+ *
+ * <p>This method acts as bridge between array-based and collection-based
+ * APIs.
+ *
+ * @return an array containing all of the elements in this collection
+ */
+ Object[] toArray();
+
+ /**
+ * Returns an array containing all of the elements in this collection;
+ * the runtime type of the returned array is that of the specified array.
+ * If the collection fits in the specified array, it is returned therein.
+ * Otherwise, a new array is allocated with the runtime type of the
+ * specified array and the size of this collection.
+ *
+ * <p>If this collection fits in the specified array with room to spare
+ * (i.e., the array has more elements than this collection), the element
+ * in the array immediately following the end of the collection is set to
+ * <tt>null</tt>. (This is useful in determining the length of this
+ * collection <i>only</i> if the caller knows that this collection does
+ * not contain any <tt>null</tt> elements.)
+ *
+ * <p>If this collection makes any guarantees as to what order its elements
+ * are returned by its iterator, this method must return the elements in
+ * the same order.
+ *
+ * <p>Like the {@link #toArray()} method, this method acts as bridge between
+ * array-based and collection-based APIs. Further, this method allows
+ * precise control over the runtime type of the output array, and may,
+ * under certain circumstances, be used to save allocation costs.
+ *
+ * <p>Suppose <tt>x</tt> is a collection known to contain only strings.
+ * The following code can be used to dump the collection into a newly
+ * allocated array of <tt>String</tt>:
+ *
+ * <pre>
+ * String[] y = x.toArray(new String[0]);</pre>
+ *
+ * Note that <tt>toArray(new Object[0])</tt> is identical in function to
+ * <tt>toArray()</tt>.
+ *
+ * @param a the array into which the elements of this collection are to be
+ * stored, if it is big enough; otherwise, a new array of the same
+ * runtime type is allocated for this purpose.
+ * @return an array containing all of the elements in this collection
+ * @throws ArrayStoreException if the runtime type of the specified array
+ * is not a supertype of the runtime type of every element in
+ * this collection
+ * @throws NullPointerException if the specified array is null
+ */
+ <T> T[] toArray(T[] a);
+
+ // Modification Operations
+
+ /**
+ * Ensures that this collection contains the specified element (optional
+ * operation). Returns <tt>true</tt> if this collection changed as a
+ * result of the call. (Returns <tt>false</tt> if this collection does
+ * not permit duplicates and already contains the specified element.)<p>
+ *
+ * Collections that support this operation may place limitations on what
+ * elements may be added to this collection. In particular, some
+ * collections will refuse to add <tt>null</tt> elements, and others will
+ * impose restrictions on the type of elements that may be added.
+ * Collection classes should clearly specify in their documentation any
+ * restrictions on what elements may be added.<p>
+ *
+ * If a collection refuses to add a particular element for any reason
+ * other than that it already contains the element, it <i>must</i> throw
+ * an exception (rather than returning <tt>false</tt>). This preserves
+ * the invariant that a collection always contains the specified element
+ * after this call returns.
+ *
+ * @param e element whose presence in this collection is to be ensured
+ * @return <tt>true</tt> if this collection changed as a result of the
+ * call
+ * @throws UnsupportedOperationException if the <tt>add</tt> operation
+ * is not supported by this collection
+ * @throws ClassCastException if the class of the specified element
+ * prevents it from being added to this collection
+ * @throws NullPointerException if the specified element is null and this
+ * collection does not permit null elements
+ * @throws IllegalArgumentException if some property of the element
+ * prevents it from being added to this collection
+ * @throws IllegalStateException if the element cannot be added at this
+ * time due to insertion restrictions
+ */
+ boolean add(E e);
+
+ /**
+ * Removes a single instance of the specified element from this
+ * collection, if it is present (optional operation). More formally,
+ * removes an element <tt>e</tt> such that
+ * <tt>(o==null ? e==null : o.equals(e))</tt>, if
+ * this collection contains one or more such elements. Returns
+ * <tt>true</tt> if this collection contained the specified element (or
+ * equivalently, if this collection changed as a result of the call).
+ *
+ * @param o element to be removed from this collection, if present
+ * @return <tt>true</tt> if an element was removed as a result of this call
+ * @throws ClassCastException if the type of the specified element
+ * is incompatible with this collection (optional)
+ * @throws NullPointerException if the specified element is null and this
+ * collection does not permit null elements (optional)
+ * @throws UnsupportedOperationException if the <tt>remove</tt> operation
+ * is not supported by this collection
+ */
+ boolean remove(Object o);
+
+
+ // Bulk Operations
+
+ /**
+ * Returns <tt>true</tt> if this collection contains all of the elements
+ * in the specified collection.
+ *
+ * @param c collection to be checked for containment in this collection
+ * @return <tt>true</tt> if this collection contains all of the elements
+ * in the specified collection
+ * @throws ClassCastException if the types of one or more elements
+ * in the specified collection are incompatible with this
+ * collection (optional)
+ * @throws NullPointerException if the specified collection contains one
+ * or more null elements and this collection does not permit null
+ * elements (optional), or if the specified collection is null
+ * @see #contains(Object)
+ */
+ boolean containsAll(Collection<?> c);
+
+ /**
+ * Adds all of the elements in the specified collection to this collection
+ * (optional operation). The behavior of this operation is undefined if
+ * the specified collection is modified while the operation is in progress.
+ * (This implies that the behavior of this call is undefined if the
+ * specified collection is this collection, and this collection is
+ * nonempty.)
+ *
+ * @param c collection containing elements to be added to this collection
+ * @return <tt>true</tt> if this collection changed as a result of the call
+ * @throws UnsupportedOperationException if the <tt>addAll</tt> operation
+ * is not supported by this collection
+ * @throws ClassCastException if the class of an element of the specified
+ * collection prevents it from being added to this collection
+ * @throws NullPointerException if the specified collection contains a
+ * null element and this collection does not permit null elements,
+ * or if the specified collection is null
+ * @throws IllegalArgumentException if some property of an element of the
+ * specified collection prevents it from being added to this
+ * collection
+ * @throws IllegalStateException if not all the elements can be added at
+ * this time due to insertion restrictions
+ * @see #add(Object)
+ */
+ boolean addAll(Collection<? extends E> c);
+
+ /**
+ * Removes all of this collection's elements that are also contained in the
+ * specified collection (optional operation). After this call returns,
+ * this collection will contain no elements in common with the specified
+ * collection.
+ *
+ * @param c collection containing elements to be removed from this collection
+ * @return <tt>true</tt> if this collection changed as a result of the
+ * call
+ * @throws UnsupportedOperationException if the <tt>removeAll</tt> method
+ * is not supported by this collection
+ * @throws ClassCastException if the types of one or more elements
+ * in this collection are incompatible with the specified
+ * collection (optional)
+ * @throws NullPointerException if this collection contains one or more
+ * null elements and the specified collection does not support
+ * null elements (optional), or if the specified collection is null
+ * @see #remove(Object)
+ * @see #contains(Object)
+ */
+ boolean removeAll(Collection<?> c);
+
+ /**
+ * Retains only the elements in this collection that are contained in the
+ * specified collection (optional operation). In other words, removes from
+ * this collection all of its elements that are not contained in the
+ * specified collection.
+ *
+ * @param c collection containing elements to be retained in this collection
+ * @return <tt>true</tt> if this collection changed as a result of the call
+ * @throws UnsupportedOperationException if the <tt>retainAll</tt> operation
+ * is not supported by this collection
+ * @throws ClassCastException if the types of one or more elements
+ * in this collection are incompatible with the specified
+ * collection (optional)
+ * @throws NullPointerException if this collection contains one or more
+ * null elements and the specified collection does not permit null
+ * elements (optional), or if the specified collection is null
+ * @see #remove(Object)
+ * @see #contains(Object)
+ */
+ boolean retainAll(Collection<?> c);
+
+ /**
+ * Removes all of the elements from this collection (optional operation).
+ * The collection will be empty after this method returns.
+ *
+ * @throws UnsupportedOperationException if the <tt>clear</tt> operation
+ * is not supported by this collection
+ */
+ void clear();
+
+
+ // Comparison and hashing
+
+ /**
+ * Compares the specified object with this collection for equality. <p>
+ *
+ * While the <tt>Collection</tt> interface adds no stipulations to the
+ * general contract for the <tt>Object.equals</tt>, programmers who
+ * implement the <tt>Collection</tt> interface "directly" (in other words,
+ * create a class that is a <tt>Collection</tt> but is not a <tt>Set</tt>
+ * or a <tt>List</tt>) must exercise care if they choose to override the
+ * <tt>Object.equals</tt>. It is not necessary to do so, and the simplest
+ * course of action is to rely on <tt>Object</tt>'s implementation, but
+ * the implementor may wish to implement a "value comparison" in place of
+ * the default "reference comparison." (The <tt>List</tt> and
+ * <tt>Set</tt> interfaces mandate such value comparisons.)<p>
+ *
+ * The general contract for the <tt>Object.equals</tt> method states that
+ * equals must be symmetric (in other words, <tt>a.equals(b)</tt> if and
+ * only if <tt>b.equals(a)</tt>). The contracts for <tt>List.equals</tt>
+ * and <tt>Set.equals</tt> state that lists are only equal to other lists,
+ * and sets to other sets. Thus, a custom <tt>equals</tt> method for a
+ * collection class that implements neither the <tt>List</tt> nor
+ * <tt>Set</tt> interface must return <tt>false</tt> when this collection
+ * is compared to any list or set. (By the same logic, it is not possible
+ * to write a class that correctly implements both the <tt>Set</tt> and
+ * <tt>List</tt> interfaces.)
+ *
+ * @param o object to be compared for equality with this collection
+ * @return <tt>true</tt> if the specified object is equal to this
+ * collection
+ *
+ * @see Object#equals(Object)
+ * @see Set#equals(Object)
+ * @see List#equals(Object)
+ */
+ boolean equals(Object o);
+
+ /**
+ * Returns the hash code value for this collection. While the
+ * <tt>Collection</tt> interface adds no stipulations to the general
+ * contract for the <tt>Object.hashCode</tt> method, programmers should
+ * take note that any class that overrides the <tt>Object.equals</tt>
+ * method must also override the <tt>Object.hashCode</tt> method in order
+ * to satisfy the general contract for the <tt>Object.hashCode</tt>method.
+ * In particular, <tt>c1.equals(c2)</tt> implies that
+ * <tt>c1.hashCode()==c2.hashCode()</tt>.
+ *
+ * @return the hash code value for this collection
+ *
+ * @see Object#hashCode()
+ * @see Object#equals(Object)
+ */
+ int hashCode();
+}