java/util/AbstractCollection.java

/*
 * 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 provides a skeletal implementation of the <tt>Collection</tt>
 * interface, to minimize the effort required to implement this interface. <p>
 *
 * To implement an unmodifiable collection, the programmer needs only to
 * extend this class and provide implementations for the <tt>iterator</tt> and
 * <tt>size</tt> methods.  (The iterator returned by the <tt>iterator</tt>
 * method must implement <tt>hasNext</tt> and <tt>next</tt>.)<p>
 *
 * To implement a modifiable collection, the programmer must additionally
 * override this class's <tt>add</tt> method (which otherwise throws an
 * <tt>UnsupportedOperationException</tt>), and the iterator returned by the
 * <tt>iterator</tt> method must additionally implement its <tt>remove</tt>
 * method.<p>
 *
 * The programmer should generally provide a void (no argument) and
 * <tt>Collection</tt> constructor, as per the recommendation in the
 * <tt>Collection</tt> interface specification.<p>
 *
 * The documentation for each non-abstract method in this class describes its
 * implementation in detail.  Each of these methods may be overridden if
 * the collection being implemented admits a more efficient implementation.<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
 * @version %I%, %G%
 * @see Collection
 * @since 1.2
 */

public abstract class AbstractCollection<E> implements Collection<E> {
    /**
     * Sole constructor.  (For invocation by subclass constructors, typically
     * implicit.)
     */
    protected AbstractCollection() {
    }

    // Query Operations

    /**
     * Returns an iterator over the elements contained in this collection.
     *
     * @return an iterator over the elements contained in this collection
     */
    public abstract Iterator<E> iterator();

    public abstract int size();

    /**
     * {@inheritDoc}
     *
     * <p>This implementation returns <tt>size() == 0</tt>.
     */
    public boolean isEmpty() {
        return size() == 0;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over the elements in the collection,
     * checking each element in turn for equality with the specified element.
     *
     * @throws ClassCastException   {@inheritDoc}
     * @throws NullPointerException {@inheritDoc}
     */
    public boolean contains(Object o) {
        Iterator<E> e = iterator();
        if (o==null) {
            while (e.hasNext())
                if (e.next()==null)
                    return true;
        } else {
            while (e.hasNext())
                if (o.equals(e.next()))
                    return true;
        }
        return false;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation returns an array containing all the elements
     * returned by this collection's iterator, in the same order, stored in
     * consecutive elements of the array, starting with index {@code 0}.
     * The length of the returned array is equal to the number of elements
     * returned by the iterator, even if the size of this collection changes
     * during iteration, as might happen if the collection permits
     * concurrent modification during iteration.  The {@code size} method is
     * called only as an optimization hint; the correct result is returned
     * even if the iterator returns a different number of elements.
     *
     * <p>This method is equivalent to:
     *
     *  <pre> {@code
     * List<E> list = new ArrayList<E>(size());
     * for (E e : this)
     *     list.add(e);
     * return list.toArray();
     * }</pre>
     */
    public Object[] toArray() {
        // Estimate size of array; be prepared to see more or fewer elements
        Object[] r = new Object[size()];
        Iterator<E> it = iterator();
        for (int i = 0; i < r.length; i++) {
            if (! it.hasNext()) // fewer elements than expected
                return Arrays.copyOf(r, i);
            r[i] = it.next();
        }
        return it.hasNext() ? finishToArray(r, it) : r;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation returns an array containing all the elements
     * returned by this collection's iterator in the same order, stored in
     * consecutive elements of the array, starting with index {@code 0}.
     * If the number of elements returned by the iterator is too large to
     * fit into the specified array, then the elements are returned in a
     * newly allocated array with length equal to the number of elements
     * returned by the iterator, even if the size of this collection
     * changes during iteration, as might happen if the collection permits
     * concurrent modification during iteration.  The {@code size} method is
     * called only as an optimization hint; the correct result is returned
     * even if the iterator returns a different number of elements.
     *
     * <p>This method is equivalent to:
     *
     *  <pre> {@code
     * List<E> list = new ArrayList<E>(size());
     * for (E e : this)
     *     list.add(e);
     * return list.toArray(a);
     * }</pre>
     *
     * @throws ArrayStoreException  {@inheritDoc}
     * @throws NullPointerException {@inheritDoc}
     */
    public <T> T[] toArray(T[] a) {
        // Estimate size of array; be prepared to see more or fewer elements
        int size = size();
        T[] r = a.length >= size ? a :
                  (T[])java.lang.reflect.Array
                  .newInstance(a.getClass().getComponentType(), size);
        Iterator<E> it = iterator();

        for (int i = 0; i < r.length; i++) {
            if (! it.hasNext()) { // fewer elements than expected
                if (a != r)
                    return Arrays.copyOf(r, i);
                r[i] = null; // null-terminate
                return r;
            }
            r[i] = (T)it.next();
        }
        return it.hasNext() ? finishToArray(r, it) : r;
    }

    /**
     * Reallocates the array being used within toArray when the iterator
     * returned more elements than expected, and finishes filling it from
     * the iterator.
     *
     * @param r the array, replete with previously stored elements
     * @param it the in-progress iterator over this collection
     * @return array containing the elements in the given array, plus any
     *         further elements returned by the iterator, trimmed to size
     */
    private static <T> T[] finishToArray(T[] r, Iterator<?> it) {
        int i = r.length;
        while (it.hasNext()) {
            int cap = r.length;
            if (i == cap) {
                int newCap = ((cap / 2) + 1) * 3;
                if (newCap <= cap) { // integer overflow
                    if (cap == Integer.MAX_VALUE)
                        throw new OutOfMemoryError
                            ("Required array size too large");
                    newCap = Integer.MAX_VALUE;
                }
                r = Arrays.copyOf(r, newCap);
            }
            r[i++] = (T)it.next();
        }
        // trim if overallocated
        return (i == r.length) ? r : Arrays.copyOf(r, i);
    }

    // Modification Operations

    /**
     * {@inheritDoc}
     *
     * <p>This implementation always throws an
     * <tt>UnsupportedOperationException</tt>.
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @throws IllegalArgumentException      {@inheritDoc}
     * @throws IllegalStateException         {@inheritDoc}
     */
    public boolean add(E e) {
        throw new UnsupportedOperationException();
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over the collection looking for the
     * specified element.  If it finds the element, it removes the element
     * from the collection using the iterator's remove method.
     *
     * <p>Note that this implementation throws an
     * <tt>UnsupportedOperationException</tt> if the iterator returned by this
     * collection's iterator method does not implement the <tt>remove</tt>
     * method and this collection contains the specified object.
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     */
    public boolean remove(Object o) {
        Iterator<E> e = iterator();
        if (o==null) {
            while (e.hasNext()) {
                if (e.next()==null) {
                    e.remove();
                    return true;
                }
            }
        } else {
            while (e.hasNext()) {
                if (o.equals(e.next())) {
                    e.remove();
                    return true;
                }
            }
        }
        return false;
    }


    // Bulk Operations

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over the specified collection,
     * checking each element returned by the iterator in turn to see
     * if it's contained in this collection.  If all elements are so
     * contained <tt>true</tt> is returned, otherwise <tt>false</tt>.
     *
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @see #contains(Object)
     */
    public boolean containsAll(Collection<?> c) {
        Iterator<?> e = c.iterator();
        while (e.hasNext())
            if (!contains(e.next()))
                return false;
        return true;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over the specified collection, and adds
     * each object returned by the iterator to this collection, in turn.
     *
     * <p>Note that this implementation will throw an
     * <tt>UnsupportedOperationException</tt> unless <tt>add</tt> is
     * overridden (assuming the specified collection is non-empty).
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @throws IllegalArgumentException      {@inheritDoc}
     * @throws IllegalStateException         {@inheritDoc}
     *
     * @see #add(Object)
     */
    public boolean addAll(Collection<? extends E> c) {
        boolean modified = false;
        Iterator<? extends E> e = c.iterator();
        while (e.hasNext()) {
            if (add(e.next()))
                modified = true;
        }
        return modified;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over this collection, checking each
     * element returned by the iterator in turn to see if it's contained
     * in the specified collection.  If it's so contained, it's removed from
     * this collection with the iterator's <tt>remove</tt> method.
     *
     * <p>Note that this implementation will throw an
     * <tt>UnsupportedOperationException</tt> if the iterator returned by the
     * <tt>iterator</tt> method does not implement the <tt>remove</tt> method
     * and this collection contains one or more elements in common with the
     * specified collection.
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     *
     * @see #remove(Object)
     * @see #contains(Object)
     */
    public boolean removeAll(Collection<?> c) {
        boolean modified = false;
        Iterator<?> e = iterator();
        while (e.hasNext()) {
            if (c.contains(e.next())) {
                e.remove();
                modified = true;
            }
        }
        return modified;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over this collection, checking each
     * element returned by the iterator in turn to see if it's contained
     * in the specified collection.  If it's not so contained, it's removed
     * from this collection with the iterator's <tt>remove</tt> method.
     *
     * <p>Note that this implementation will throw an
     * <tt>UnsupportedOperationException</tt> if the iterator returned by the
     * <tt>iterator</tt> method does not implement the <tt>remove</tt> method
     * and this collection contains one or more elements not present in the
     * specified collection.
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     *
     * @see #remove(Object)
     * @see #contains(Object)
     */
    public boolean retainAll(Collection<?> c) {
        boolean modified = false;
        Iterator<E> e = iterator();
        while (e.hasNext()) {
            if (!c.contains(e.next())) {
                e.remove();
                modified = true;
            }
        }
        return modified;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over this collection, removing each
     * element using the <tt>Iterator.remove</tt> operation.  Most
     * implementations will probably choose to override this method for
     * efficiency.
     *
     * <p>Note that this implementation will throw an
     * <tt>UnsupportedOperationException</tt> if the iterator returned by this
     * collection's <tt>iterator</tt> method does not implement the
     * <tt>remove</tt> method and this collection is non-empty.
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     */
    public void clear() {
        Iterator<E> e = iterator();
        while (e.hasNext()) {
            e.next();
            e.remove();
        }
    }


    //  String conversion

    /**
     * Returns a string representation of this collection.  The string
     * representation consists of a list of the collection's elements in the
     * order they are returned by its iterator, enclosed in square brackets
     * (<tt>"[]"</tt>).  Adjacent elements are separated by the characters
     * <tt>", "</tt> (comma and space).  Elements are converted to strings as
     * by {@link String#valueOf(Object)}.
     *
     * @return a string representation of this collection
     */
    public String toString() {
        Iterator<E> i = iterator();
        if (! i.hasNext())
            return "[]";

        StringBuilder sb = new StringBuilder();
        sb.append('[');
        for (;;) {
            E e = i.next();
            sb.append(e == this ? "(this Collection)" : e);
            if (! i.hasNext())
                return sb.append(']').toString();
            sb.append(", ");
        }
    }

}
Revision:	1.12
Committed:	Sun May 18 23:47:55 2008 UTC (16 years ago) by jsr166
Branch:	MAIN
Changes since 1.11:	+102 -102 lines
Log Message:	Sync with OpenJDK; untabify
#	User	Rev	Content
1	dl	1.1	/*
2	jsr166	1.11	* Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
3			* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4	dl	1.1	*
5	jsr166	1.11	* This code is free software; you can redistribute it and/or modify it
6			* under the terms of the GNU General Public License version 2 only, as
7			* published by the Free Software Foundation. Sun designates this
8			* particular file as subject to the "Classpath" exception as provided
9			* by Sun in the LICENSE file that accompanied this code.
10			*
11			* This code is distributed in the hope that it will be useful, but WITHOUT
12			* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13			* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14			* version 2 for more details (a copy is included in the LICENSE file that
15			* accompanied this code).
16			*
17			* You should have received a copy of the GNU General Public License version
18			* 2 along with this work; if not, write to the Free Software Foundation,
19			* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20			*
21			* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22			* CA 95054 USA or visit www.sun.com if you need additional information or
23			* have any questions.
24	dl	1.1	*/
25
26			package java.util;
27
28			/**
29			* This class provides a skeletal implementation of the <tt>Collection</tt>
30			* interface, to minimize the effort required to implement this interface. <p>
31			*
32			* To implement an unmodifiable collection, the programmer needs only to
33			* extend this class and provide implementations for the <tt>iterator</tt> and
34			* <tt>size</tt> methods. (The iterator returned by the <tt>iterator</tt>
35			* method must implement <tt>hasNext</tt> and <tt>next</tt>.)<p>
36			*
37			* To implement a modifiable collection, the programmer must additionally
38			* override this class's <tt>add</tt> method (which otherwise throws an
39			* <tt>UnsupportedOperationException</tt>), and the iterator returned by the
40			* <tt>iterator</tt> method must additionally implement its <tt>remove</tt>
41			* method.<p>
42			*
43			* The programmer should generally provide a void (no argument) and
44			* <tt>Collection</tt> constructor, as per the recommendation in the
45			* <tt>Collection</tt> interface specification.<p>
46			*
47	jsr166	1.9	* The documentation for each non-abstract method in this class describes its
48	dl	1.1	* implementation in detail. Each of these methods may be overridden if
49			* the collection being implemented admits a more efficient implementation.<p>
50			*
51			* This class is a member of the
52	jsr166	1.8	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
53	dl	1.1	* Java Collections Framework</a>.
54			*
55			* @author Josh Bloch
56			* @author Neal Gafter
57	jsr166	1.6	* @version %I%, %G%
58	dl	1.1	* @see Collection
59			* @since 1.2
60			*/
61
62			public abstract class AbstractCollection<E> implements Collection<E> {
63			/**
64			* Sole constructor. (For invocation by subclass constructors, typically
65			* implicit.)
66			*/
67			protected AbstractCollection() {
68			}
69
70			// Query Operations
71
72			/**
73			* Returns an iterator over the elements contained in this collection.
74			*
75			* @return an iterator over the elements contained in this collection
76			*/
77			public abstract Iterator<E> iterator();
78
79			public abstract int size();
80
81			/**
82			* {@inheritDoc}
83			*
84			* <p>This implementation returns <tt>size() == 0</tt>.
85			*/
86			public boolean isEmpty() {
87	jsr166	1.12	return size() == 0;
88	dl	1.1	}
89
90			/**
91			* {@inheritDoc}
92			*
93			* <p>This implementation iterates over the elements in the collection,
94			* checking each element in turn for equality with the specified element.
95			*
96			* @throws ClassCastException {@inheritDoc}
97			* @throws NullPointerException {@inheritDoc}
98			*/
99			public boolean contains(Object o) {
100	jsr166	1.12	Iterator<E> e = iterator();
101			if (o==null) {
102			while (e.hasNext())
103			if (e.next()==null)
104			return true;
105			} else {
106			while (e.hasNext())
107			if (o.equals(e.next()))
108			return true;
109			}
110			return false;
111	dl	1.1	}
112
113			/**
114			* {@inheritDoc}
115			*
116	jsr166	1.9	* <p>This implementation returns an array containing all the elements
117			* returned by this collection's iterator, in the same order, stored in
118			* consecutive elements of the array, starting with index {@code 0}.
119			* The length of the returned array is equal to the number of elements
120			* returned by the iterator, even if the size of this collection changes
121			* during iteration, as might happen if the collection permits
122			* concurrent modification during iteration. The {@code size} method is
123			* called only as an optimization hint; the correct result is returned
124			* even if the iterator returns a different number of elements.
125			*
126			* <p>This method is equivalent to:
127			*
128			* <pre> {@code
129			* List<E> list = new ArrayList<E>(size());
130			* for (E e : this)
131			* list.add(e);
132			* return list.toArray();
133			* }</pre>
134	dl	1.1	*/
135			public Object[] toArray() {
136			// Estimate size of array; be prepared to see more or fewer elements
137	jsr166	1.12	Object[] r = new Object[size()];
138	jsr166	1.3	Iterator<E> it = iterator();
139	jsr166	1.12	for (int i = 0; i < r.length; i++) {
140			if (! it.hasNext()) // fewer elements than expected
141			return Arrays.copyOf(r, i);
142			r[i] = it.next();
143			}
144			return it.hasNext() ? finishToArray(r, it) : r;
145	dl	1.1	}
146
147			/**
148			* {@inheritDoc}
149			*
150	jsr166	1.9	* <p>This implementation returns an array containing all the elements
151			* returned by this collection's iterator in the same order, stored in
152			* consecutive elements of the array, starting with index {@code 0}.
153			* If the number of elements returned by the iterator is too large to
154			* fit into the specified array, then the elements are returned in a
155			* newly allocated array with length equal to the number of elements
156			* returned by the iterator, even if the size of this collection
157			* changes during iteration, as might happen if the collection permits
158			* concurrent modification during iteration. The {@code size} method is
159			* called only as an optimization hint; the correct result is returned
160			* even if the iterator returns a different number of elements.
161			*
162			* <p>This method is equivalent to:
163			*
164			* <pre> {@code
165			* List<E> list = new ArrayList<E>(size());
166			* for (E e : this)
167			* list.add(e);
168			* return list.toArray(a);
169			* }</pre>
170	dl	1.1	*
171			* @throws ArrayStoreException {@inheritDoc}
172			* @throws NullPointerException {@inheritDoc}
173			*/
174			public <T> T[] toArray(T[] a) {
175			// Estimate size of array; be prepared to see more or fewer elements
176			int size = size();
177	jsr166	1.3	T[] r = a.length >= size ? a :
178	dl	1.1	(T[])java.lang.reflect.Array
179			.newInstance(a.getClass().getComponentType(), size);
180	jsr166	1.3	Iterator<E> it = iterator();
181	jsr166	1.9
182	jsr166	1.12	for (int i = 0; i < r.length; i++) {
183			if (! it.hasNext()) { // fewer elements than expected
184			if (a != r)
185			return Arrays.copyOf(r, i);
186			r[i] = null; // null-terminate
187			return r;
188			}
189			r[i] = (T)it.next();
190			}
191			return it.hasNext() ? finishToArray(r, it) : r;
192	dl	1.1	}
193
194			/**
195	jsr166	1.9	* Reallocates the array being used within toArray when the iterator
196			* returned more elements than expected, and finishes filling it from
197			* the iterator.
198			*
199			* @param r the array, replete with previously stored elements
200			* @param it the in-progress iterator over this collection
201	jsr166	1.3	* @return array containing the elements in the given array, plus any
202			* further elements returned by the iterator, trimmed to size
203	dl	1.1	*/
204	jsr166	1.9	private static <T> T[] finishToArray(T[] r, Iterator<?> it) {
205	jsr166	1.12	int i = r.length;
206	jsr166	1.2	while (it.hasNext()) {
207	dl	1.1	int cap = r.length;
208	jsr166	1.9	if (i == cap) {
209	dl	1.4	int newCap = ((cap / 2) + 1) * 3;
210			if (newCap <= cap) { // integer overflow
211	jsr166	1.12	if (cap == Integer.MAX_VALUE)
212			throw new OutOfMemoryError
213			("Required array size too large");
214			newCap = Integer.MAX_VALUE;
215			}
216			r = Arrays.copyOf(r, newCap);
217			}
218			r[i++] = (T)it.next();
219	jsr166	1.7	}
220	dl	1.1	// trim if overallocated
221	jsr166	1.9	return (i == r.length) ? r : Arrays.copyOf(r, i);
222	dl	1.1	}
223
224			// Modification Operations
225
226			/**
227			* {@inheritDoc}
228			*
229			* <p>This implementation always throws an
230			* <tt>UnsupportedOperationException</tt>.
231			*
232			* @throws UnsupportedOperationException {@inheritDoc}
233			* @throws ClassCastException {@inheritDoc}
234			* @throws NullPointerException {@inheritDoc}
235			* @throws IllegalArgumentException {@inheritDoc}
236			* @throws IllegalStateException {@inheritDoc}
237			*/
238			public boolean add(E e) {
239	jsr166	1.12	throw new UnsupportedOperationException();
240	dl	1.1	}
241
242			/**
243			* {@inheritDoc}
244			*
245			* <p>This implementation iterates over the collection looking for the
246			* specified element. If it finds the element, it removes the element
247			* from the collection using the iterator's remove method.
248			*
249			* <p>Note that this implementation throws an
250			* <tt>UnsupportedOperationException</tt> if the iterator returned by this
251			* collection's iterator method does not implement the <tt>remove</tt>
252			* method and this collection contains the specified object.
253			*
254			* @throws UnsupportedOperationException {@inheritDoc}
255			* @throws ClassCastException {@inheritDoc}
256			* @throws NullPointerException {@inheritDoc}
257			*/
258			public boolean remove(Object o) {
259	jsr166	1.12	Iterator<E> e = iterator();
260			if (o==null) {
261			while (e.hasNext()) {
262			if (e.next()==null) {
263			e.remove();
264			return true;
265			}
266			}
267			} else {
268			while (e.hasNext()) {
269			if (o.equals(e.next())) {
270			e.remove();
271			return true;
272			}
273			}
274			}
275			return false;
276	dl	1.1	}
277
278
279			// Bulk Operations
280
281			/**
282			* {@inheritDoc}
283			*
284			* <p>This implementation iterates over the specified collection,
285			* checking each element returned by the iterator in turn to see
286			* if it's contained in this collection. If all elements are so
287			* contained <tt>true</tt> is returned, otherwise <tt>false</tt>.
288			*
289			* @throws ClassCastException {@inheritDoc}
290			* @throws NullPointerException {@inheritDoc}
291			* @see #contains(Object)
292			*/
293			public boolean containsAll(Collection<?> c) {
294	jsr166	1.12	Iterator<?> e = c.iterator();
295			while (e.hasNext())
296			if (!contains(e.next()))
297			return false;
298			return true;
299	dl	1.1	}
300
301			/**
302			* {@inheritDoc}
303			*
304			* <p>This implementation iterates over the specified collection, and adds
305			* each object returned by the iterator to this collection, in turn.
306			*
307			* <p>Note that this implementation will throw an
308			* <tt>UnsupportedOperationException</tt> unless <tt>add</tt> is
309			* overridden (assuming the specified collection is non-empty).
310			*
311			* @throws UnsupportedOperationException {@inheritDoc}
312			* @throws ClassCastException {@inheritDoc}
313			* @throws NullPointerException {@inheritDoc}
314			* @throws IllegalArgumentException {@inheritDoc}
315			* @throws IllegalStateException {@inheritDoc}
316			*
317			* @see #add(Object)
318			*/
319			public boolean addAll(Collection<? extends E> c) {
320	jsr166	1.12	boolean modified = false;
321			Iterator<? extends E> e = c.iterator();
322			while (e.hasNext()) {
323			if (add(e.next()))
324			modified = true;
325			}
326			return modified;
327	dl	1.1	}
328
329			/**
330			* {@inheritDoc}
331			*
332			* <p>This implementation iterates over this collection, checking each
333			* element returned by the iterator in turn to see if it's contained
334			* in the specified collection. If it's so contained, it's removed from
335			* this collection with the iterator's <tt>remove</tt> method.
336			*
337			* <p>Note that this implementation will throw an
338			* <tt>UnsupportedOperationException</tt> if the iterator returned by the
339			* <tt>iterator</tt> method does not implement the <tt>remove</tt> method
340			* and this collection contains one or more elements in common with the
341			* specified collection.
342			*
343			* @throws UnsupportedOperationException {@inheritDoc}
344			* @throws ClassCastException {@inheritDoc}
345			* @throws NullPointerException {@inheritDoc}
346			*
347			* @see #remove(Object)
348			* @see #contains(Object)
349			*/
350			public boolean removeAll(Collection<?> c) {
351	jsr166	1.12	boolean modified = false;
352			Iterator<?> e = iterator();
353			while (e.hasNext()) {
354			if (c.contains(e.next())) {
355			e.remove();
356			modified = true;
357			}
358			}
359			return modified;
360	dl	1.1	}
361
362			/**
363			* {@inheritDoc}
364			*
365			* <p>This implementation iterates over this collection, checking each
366			* element returned by the iterator in turn to see if it's contained
367			* in the specified collection. If it's not so contained, it's removed
368			* from this collection with the iterator's <tt>remove</tt> method.
369			*
370			* <p>Note that this implementation will throw an
371			* <tt>UnsupportedOperationException</tt> if the iterator returned by the
372			* <tt>iterator</tt> method does not implement the <tt>remove</tt> method
373			* and this collection contains one or more elements not present in the
374			* specified collection.
375			*
376			* @throws UnsupportedOperationException {@inheritDoc}
377			* @throws ClassCastException {@inheritDoc}
378			* @throws NullPointerException {@inheritDoc}
379			*
380			* @see #remove(Object)
381			* @see #contains(Object)
382			*/
383			public boolean retainAll(Collection<?> c) {
384	jsr166	1.12	boolean modified = false;
385			Iterator<E> e = iterator();
386			while (e.hasNext()) {
387			if (!c.contains(e.next())) {
388			e.remove();
389			modified = true;
390			}
391			}
392			return modified;
393	dl	1.1	}
394
395			/**
396			* {@inheritDoc}
397			*
398			* <p>This implementation iterates over this collection, removing each
399			* element using the <tt>Iterator.remove</tt> operation. Most
400			* implementations will probably choose to override this method for
401			* efficiency.
402			*
403			* <p>Note that this implementation will throw an
404			* <tt>UnsupportedOperationException</tt> if the iterator returned by this
405			* collection's <tt>iterator</tt> method does not implement the
406			* <tt>remove</tt> method and this collection is non-empty.
407			*
408			* @throws UnsupportedOperationException {@inheritDoc}
409			*/
410			public void clear() {
411	jsr166	1.12	Iterator<E> e = iterator();
412			while (e.hasNext()) {
413			e.next();
414			e.remove();
415			}
416	dl	1.1	}
417
418
419			// String conversion
420
421			/**
422			* Returns a string representation of this collection. The string
423			* representation consists of a list of the collection's elements in the
424			* order they are returned by its iterator, enclosed in square brackets
425			* (<tt>"[]"</tt>). Adjacent elements are separated by the characters
426			* <tt>", "</tt> (comma and space). Elements are converted to strings as
427			* by {@link String#valueOf(Object)}.
428			*
429			* @return a string representation of this collection
430			*/
431			public String toString() {
432			Iterator<E> i = iterator();
433	jsr166	1.12	if (! i.hasNext())
434			return "[]";
435	dl	1.1
436	jsr166	1.12	StringBuilder sb = new StringBuilder();
437			sb.append('[');
438			for (;;) {
439			E e = i.next();
440			sb.append(e == this ? "(this Collection)" : e);
441			if (! i.hasNext())
442			return sb.append(']').toString();
443			sb.append(", ");
444			}
445	dl	1.1	}
446
447			}