java/util/AbstractCollection.java

/*
 * Copyright (c) 1997, 2006, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.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
 * @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> it = iterator();
        if (o==null) {
            while (it.hasNext())
                if (it.next()==null)
                    return true;
        } else {
            while (it.hasNext())
                if (o.equals(it.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> it = iterator();
        if (o==null) {
            while (it.hasNext()) {
                if (it.next()==null) {
                    it.remove();
                    return true;
                }
            }
        } else {
            while (it.hasNext()) {
                if (o.equals(it.next())) {
                    it.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) {
        for (Object e : c)
            if (!contains(e))
                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;
        for (E e : c)
            if (add(e))
                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<?> it = iterator();
        while (it.hasNext()) {
            if (c.contains(it.next())) {
                it.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> it = iterator();
        while (it.hasNext()) {
            if (!c.contains(it.next())) {
                it.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> it = iterator();
        while (it.hasNext()) {
            it.next();
            it.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> it = iterator();
        if (! it.hasNext())
            return "[]";

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

}
Revision:	1.18
Committed:	Sat May 7 12:22:02 2011 UTC (13 years ago) by dl
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.17:	+0 -0 lines
State:	*FILE REMOVED*
Log Message:	Stop shadowing OpenJDK classes not originated by jsr166
#	Content
1	/*
2	* Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved.
3	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4	*
5	* 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22	* or visit www.oracle.com if you need additional information or have any
23	* questions.
24	*/
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	* The documentation for each non-abstract method in this class describes its
48	* 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	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
53	* Java Collections Framework</a>.
54	*
55	* @author Josh Bloch
56	* @author Neal Gafter
57	* @see Collection
58	* @since 1.2
59	*/
60
61	public abstract class AbstractCollection<E> implements Collection<E> {
62	/**
63	* Sole constructor. (For invocation by subclass constructors, typically
64	* implicit.)
65	*/
66	protected AbstractCollection() {
67	}
68
69	// Query Operations
70
71	/**
72	* Returns an iterator over the elements contained in this collection.
73	*
74	* @return an iterator over the elements contained in this collection
75	*/
76	public abstract Iterator<E> iterator();
77
78	public abstract int size();
79
80	/**
81	* {@inheritDoc}
82	*
83	* <p>This implementation returns <tt>size() == 0</tt>.
84	*/
85	public boolean isEmpty() {
86	return size() == 0;
87	}
88
89	/**
90	* {@inheritDoc}
91	*
92	* <p>This implementation iterates over the elements in the collection,
93	* checking each element in turn for equality with the specified element.
94	*
95	* @throws ClassCastException {@inheritDoc}
96	* @throws NullPointerException {@inheritDoc}
97	*/
98	public boolean contains(Object o) {
99	Iterator<E> it = iterator();
100	if (o==null) {
101	while (it.hasNext())
102	if (it.next()==null)
103	return true;
104	} else {
105	while (it.hasNext())
106	if (o.equals(it.next()))
107	return true;
108	}
109	return false;
110	}
111
112	/**
113	* {@inheritDoc}
114	*
115	* <p>This implementation returns an array containing all the elements
116	* returned by this collection's iterator, in the same order, stored in
117	* consecutive elements of the array, starting with index {@code 0}.
118	* The length of the returned array is equal to the number of elements
119	* returned by the iterator, even if the size of this collection changes
120	* during iteration, as might happen if the collection permits
121	* concurrent modification during iteration. The {@code size} method is
122	* called only as an optimization hint; the correct result is returned
123	* even if the iterator returns a different number of elements.
124	*
125	* <p>This method is equivalent to:
126	*
127	* <pre> {@code
128	* List<E> list = new ArrayList<E>(size());
129	* for (E e : this)
130	* list.add(e);
131	* return list.toArray();
132	* }</pre>
133	*/
134	public Object[] toArray() {
135	// Estimate size of array; be prepared to see more or fewer elements
136	Object[] r = new Object[size()];
137	Iterator<E> it = iterator();
138	for (int i = 0; i < r.length; i++) {
139	if (! it.hasNext()) // fewer elements than expected
140	return Arrays.copyOf(r, i);
141	r[i] = it.next();
142	}
143	return it.hasNext() ? finishToArray(r, it) : r;
144	}
145
146	/**
147	* {@inheritDoc}
148	*
149	* <p>This implementation returns an array containing all the elements
150	* returned by this collection's iterator in the same order, stored in
151	* consecutive elements of the array, starting with index {@code 0}.
152	* If the number of elements returned by the iterator is too large to
153	* fit into the specified array, then the elements are returned in a
154	* newly allocated array with length equal to the number of elements
155	* returned by the iterator, even if the size of this collection
156	* changes during iteration, as might happen if the collection permits
157	* concurrent modification during iteration. The {@code size} method is
158	* called only as an optimization hint; the correct result is returned
159	* even if the iterator returns a different number of elements.
160	*
161	* <p>This method is equivalent to:
162	*
163	* <pre> {@code
164	* List<E> list = new ArrayList<E>(size());
165	* for (E e : this)
166	* list.add(e);
167	* return list.toArray(a);
168	* }</pre>
169	*
170	* @throws ArrayStoreException {@inheritDoc}
171	* @throws NullPointerException {@inheritDoc}
172	*/
173	public <T> T[] toArray(T[] a) {
174	// Estimate size of array; be prepared to see more or fewer elements
175	int size = size();
176	T[] r = a.length >= size ? a :
177	(T[])java.lang.reflect.Array
178	.newInstance(a.getClass().getComponentType(), size);
179	Iterator<E> it = iterator();
180
181	for (int i = 0; i < r.length; i++) {
182	if (! it.hasNext()) { // fewer elements than expected
183	if (a != r)
184	return Arrays.copyOf(r, i);
185	r[i] = null; // null-terminate
186	return r;
187	}
188	r[i] = (T)it.next();
189	}
190	return it.hasNext() ? finishToArray(r, it) : r;
191	}
192
193	/**
194	* Reallocates the array being used within toArray when the iterator
195	* returned more elements than expected, and finishes filling it from
196	* the iterator.
197	*
198	* @param r the array, replete with previously stored elements
199	* @param it the in-progress iterator over this collection
200	* @return array containing the elements in the given array, plus any
201	* further elements returned by the iterator, trimmed to size
202	*/
203	private static <T> T[] finishToArray(T[] r, Iterator<?> it) {
204	int i = r.length;
205	while (it.hasNext()) {
206	int cap = r.length;
207	if (i == cap) {
208	int newCap = ((cap / 2) + 1) * 3;
209	if (newCap <= cap) { // integer overflow
210	if (cap == Integer.MAX_VALUE)
211	throw new OutOfMemoryError
212	("Required array size too large");
213	newCap = Integer.MAX_VALUE;
214	}
215	r = Arrays.copyOf(r, newCap);
216	}
217	r[i++] = (T)it.next();
218	}
219	// trim if overallocated
220	return (i == r.length) ? r : Arrays.copyOf(r, i);
221	}
222
223	// Modification Operations
224
225	/**
226	* {@inheritDoc}
227	*
228	* <p>This implementation always throws an
229	* <tt>UnsupportedOperationException</tt>.
230	*
231	* @throws UnsupportedOperationException {@inheritDoc}
232	* @throws ClassCastException {@inheritDoc}
233	* @throws NullPointerException {@inheritDoc}
234	* @throws IllegalArgumentException {@inheritDoc}
235	* @throws IllegalStateException {@inheritDoc}
236	*/
237	public boolean add(E e) {
238	throw new UnsupportedOperationException();
239	}
240
241	/**
242	* {@inheritDoc}
243	*
244	* <p>This implementation iterates over the collection looking for the
245	* specified element. If it finds the element, it removes the element
246	* from the collection using the iterator's remove method.
247	*
248	* <p>Note that this implementation throws an
249	* <tt>UnsupportedOperationException</tt> if the iterator returned by this
250	* collection's iterator method does not implement the <tt>remove</tt>
251	* method and this collection contains the specified object.
252	*
253	* @throws UnsupportedOperationException {@inheritDoc}
254	* @throws ClassCastException {@inheritDoc}
255	* @throws NullPointerException {@inheritDoc}
256	*/
257	public boolean remove(Object o) {
258	Iterator<E> it = iterator();
259	if (o==null) {
260	while (it.hasNext()) {
261	if (it.next()==null) {
262	it.remove();
263	return true;
264	}
265	}
266	} else {
267	while (it.hasNext()) {
268	if (o.equals(it.next())) {
269	it.remove();
270	return true;
271	}
272	}
273	}
274	return false;
275	}
276
277
278	// Bulk Operations
279
280	/**
281	* {@inheritDoc}
282	*
283	* <p>This implementation iterates over the specified collection,
284	* checking each element returned by the iterator in turn to see
285	* if it's contained in this collection. If all elements are so
286	* contained <tt>true</tt> is returned, otherwise <tt>false</tt>.
287	*
288	* @throws ClassCastException {@inheritDoc}
289	* @throws NullPointerException {@inheritDoc}
290	* @see #contains(Object)
291	*/
292	public boolean containsAll(Collection<?> c) {
293	for (Object e : c)
294	if (!contains(e))
295	return false;
296	return true;
297	}
298
299	/**
300	* {@inheritDoc}
301	*
302	* <p>This implementation iterates over the specified collection, and adds
303	* each object returned by the iterator to this collection, in turn.
304	*
305	* <p>Note that this implementation will throw an
306	* <tt>UnsupportedOperationException</tt> unless <tt>add</tt> is
307	* overridden (assuming the specified collection is non-empty).
308	*
309	* @throws UnsupportedOperationException {@inheritDoc}
310	* @throws ClassCastException {@inheritDoc}
311	* @throws NullPointerException {@inheritDoc}
312	* @throws IllegalArgumentException {@inheritDoc}
313	* @throws IllegalStateException {@inheritDoc}
314	*
315	* @see #add(Object)
316	*/
317	public boolean addAll(Collection<? extends E> c) {
318	boolean modified = false;
319	for (E e : c)
320	if (add(e))
321	modified = true;
322	return modified;
323	}
324
325	/**
326	* {@inheritDoc}
327	*
328	* <p>This implementation iterates over this collection, checking each
329	* element returned by the iterator in turn to see if it's contained
330	* in the specified collection. If it's so contained, it's removed from
331	* this collection with the iterator's <tt>remove</tt> method.
332	*
333	* <p>Note that this implementation will throw an
334	* <tt>UnsupportedOperationException</tt> if the iterator returned by the
335	* <tt>iterator</tt> method does not implement the <tt>remove</tt> method
336	* and this collection contains one or more elements in common with the
337	* specified collection.
338	*
339	* @throws UnsupportedOperationException {@inheritDoc}
340	* @throws ClassCastException {@inheritDoc}
341	* @throws NullPointerException {@inheritDoc}
342	*
343	* @see #remove(Object)
344	* @see #contains(Object)
345	*/
346	public boolean removeAll(Collection<?> c) {
347	boolean modified = false;
348	Iterator<?> it = iterator();
349	while (it.hasNext()) {
350	if (c.contains(it.next())) {
351	it.remove();
352	modified = true;
353	}
354	}
355	return modified;
356	}
357
358	/**
359	* {@inheritDoc}
360	*
361	* <p>This implementation iterates over this collection, checking each
362	* element returned by the iterator in turn to see if it's contained
363	* in the specified collection. If it's not so contained, it's removed
364	* from this collection with the iterator's <tt>remove</tt> method.
365	*
366	* <p>Note that this implementation will throw an
367	* <tt>UnsupportedOperationException</tt> if the iterator returned by the
368	* <tt>iterator</tt> method does not implement the <tt>remove</tt> method
369	* and this collection contains one or more elements not present in the
370	* specified collection.
371	*
372	* @throws UnsupportedOperationException {@inheritDoc}
373	* @throws ClassCastException {@inheritDoc}
374	* @throws NullPointerException {@inheritDoc}
375	*
376	* @see #remove(Object)
377	* @see #contains(Object)
378	*/
379	public boolean retainAll(Collection<?> c) {
380	boolean modified = false;
381	Iterator<E> it = iterator();
382	while (it.hasNext()) {
383	if (!c.contains(it.next())) {
384	it.remove();
385	modified = true;
386	}
387	}
388	return modified;
389	}
390
391	/**
392	* {@inheritDoc}
393	*
394	* <p>This implementation iterates over this collection, removing each
395	* element using the <tt>Iterator.remove</tt> operation. Most
396	* implementations will probably choose to override this method for
397	* efficiency.
398	*
399	* <p>Note that this implementation will throw an
400	* <tt>UnsupportedOperationException</tt> if the iterator returned by this
401	* collection's <tt>iterator</tt> method does not implement the
402	* <tt>remove</tt> method and this collection is non-empty.
403	*
404	* @throws UnsupportedOperationException {@inheritDoc}
405	*/
406	public void clear() {
407	Iterator<E> it = iterator();
408	while (it.hasNext()) {
409	it.next();
410	it.remove();
411	}
412	}
413
414
415	// String conversion
416
417	/**
418	* Returns a string representation of this collection. The string
419	* representation consists of a list of the collection's elements in the
420	* order they are returned by its iterator, enclosed in square brackets
421	* (<tt>"[]"</tt>). Adjacent elements are separated by the characters
422	* <tt>", "</tt> (comma and space). Elements are converted to strings as
423	* by {@link String#valueOf(Object)}.
424	*
425	* @return a string representation of this collection
426	*/
427	public String toString() {
428	Iterator<E> it = iterator();
429	if (! it.hasNext())
430	return "[]";
431
432	StringBuilder sb = new StringBuilder();
433	sb.append('[');
434	for (;;) {
435	E e = it.next();
436	sb.append(e == this ? "(this Collection)" : e);
437	if (! it.hasNext())
438	return sb.append(']').toString();
439	sb.append(',').append(' ');
440	}
441	}
442
443	}