java/util/AbstractCollection.java

/*
 * @(#)AbstractCollection.java  1.33 05/09/09
 *
 * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

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 methods 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}/../guide/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @author  Josh Bloch
 * @author  Neal Gafter
 * @version 1.24, 01/18/03
 * @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 allocates the array to be returned, and iterates
     * over the elements in the collection, storing each object reference in
     * the next consecutive element of the array, starting with element 0.
     */
    public Object[] toArray() {
        // Estimate size of array; be prepared to see more or fewer elements
        Object[] r = new Object[size()];
        int i = 0;
        Iterator it = iterator();
        while (i < r.length && it.hasNext())
            r[i++] = it.next();
        // Trim if overallocated; expand if underallocated
        if (i < r.length || it.hasNext())
            return resizeAndFinishToArray(r, i, it);
        return r;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation checks if the array is large enough to contain the
     * collection; if not, it allocates a new array of the correct size and
     * type (using reflection).  Then, it iterates over the collection,
     * storing each object reference in the next consecutive element of the
     * array, starting with element 0.  If the array is larger than the
     * collection, a <tt>null</tt> is stored in the first location after the
     * end of the collection.
     *
     * @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);
        int i = 0;
        Iterator it = iterator();
        while (i < r.length && it.hasNext())
            r[i++] = (T)it.next();
        // Trim if overallocated; expand if underallocated
        if (it.hasNext() || (r != a && i < r.length))
            return resizeAndFinishToArray(r, i, it);
        if (i < r.length)
            r[i] = null; // null-terminate if provided array is too big
        return r;
    }

    /**
     * Reallocate the array being used within toArray that has a
     * different number of elements than expected, and finish filling
     * it if necessary
     * @param r the array
     * @param i the next array index to fill
     * @param it the in-progress iterator over the collection
     * @return larger array containing same elements
     */
    private static <T> T[] resizeAndFinishToArray(T[] r, int i, Iterator it) {
        while (it.hasNext()) {
            int cap = r.length;
            if (i < cap)
                r[i++] = (T)it.next();
            else if (cap < Integer.MAX_VALUE) { // expand
                int newCap = (cap * 3) / 2 + 1;
                if (newCap <= cap) // integer overflow
                    newCap = Integer.MAX_VALUE;
                r = Arrays.copyOf(r, newCap);
            } else // can't expand
                throw new OutOfMemoryError("Required array size too large");
        }
        // 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:	1.2
Committed:	Wed Nov 23 05:33:25 2005 UTC (18 years, 6 months ago) by jsr166
Branch:	MAIN
Changes since 1.1:	+5 -5 lines
Log Message:	whitespace
#	User	Rev	Content
1	dl	1.1	/*
2			* @(#)AbstractCollection.java 1.33 05/09/09
3			*
4			* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
5			* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6			*/
7
8			package java.util;
9
10			/**
11			* This class provides a skeletal implementation of the <tt>Collection</tt>
12			* interface, to minimize the effort required to implement this interface. <p>
13			*
14			* To implement an unmodifiable collection, the programmer needs only to
15			* extend this class and provide implementations for the <tt>iterator</tt> and
16			* <tt>size</tt> methods. (The iterator returned by the <tt>iterator</tt>
17			* method must implement <tt>hasNext</tt> and <tt>next</tt>.)<p>
18			*
19			* To implement a modifiable collection, the programmer must additionally
20			* override this class's <tt>add</tt> method (which otherwise throws an
21			* <tt>UnsupportedOperationException</tt>), and the iterator returned by the
22			* <tt>iterator</tt> method must additionally implement its <tt>remove</tt>
23			* method.<p>
24			*
25			* The programmer should generally provide a void (no argument) and
26			* <tt>Collection</tt> constructor, as per the recommendation in the
27			* <tt>Collection</tt> interface specification.<p>
28			*
29			* The documentation for each non-abstract methods in this class describes its
30			* implementation in detail. Each of these methods may be overridden if
31			* the collection being implemented admits a more efficient implementation.<p>
32			*
33			* This class is a member of the
34			* <a href="{@docRoot}/../guide/collections/index.html">
35			* Java Collections Framework</a>.
36			*
37			* @author Josh Bloch
38			* @author Neal Gafter
39			* @version 1.24, 01/18/03
40			* @see Collection
41			* @since 1.2
42			*/
43
44			public abstract class AbstractCollection<E> implements Collection<E> {
45			/**
46			* Sole constructor. (For invocation by subclass constructors, typically
47			* implicit.)
48			*/
49			protected AbstractCollection() {
50			}
51
52			// Query Operations
53
54			/**
55			* Returns an iterator over the elements contained in this collection.
56			*
57			* @return an iterator over the elements contained in this collection
58			*/
59			public abstract Iterator<E> iterator();
60
61			public abstract int size();
62
63			/**
64			* {@inheritDoc}
65			*
66			* <p>This implementation returns <tt>size() == 0</tt>.
67			*/
68			public boolean isEmpty() {
69			return size() == 0;
70			}
71
72			/**
73			* {@inheritDoc}
74			*
75			* <p>This implementation iterates over the elements in the collection,
76			* checking each element in turn for equality with the specified element.
77			*
78			* @throws ClassCastException {@inheritDoc}
79			* @throws NullPointerException {@inheritDoc}
80			*/
81			public boolean contains(Object o) {
82			Iterator<E> e = iterator();
83			if (o==null) {
84			while (e.hasNext())
85			if (e.next()==null)
86			return true;
87			} else {
88			while (e.hasNext())
89			if (o.equals(e.next()))
90			return true;
91			}
92			return false;
93			}
94
95			/**
96			* {@inheritDoc}
97			*
98			* <p>This implementation allocates the array to be returned, and iterates
99			* over the elements in the collection, storing each object reference in
100			* the next consecutive element of the array, starting with element 0.
101			*/
102			public Object[] toArray() {
103			// Estimate size of array; be prepared to see more or fewer elements
104			Object[] r = new Object[size()];
105			int i = 0;
106			Iterator it = iterator();
107	jsr166	1.2	while (i < r.length && it.hasNext())
108	dl	1.1	r[i++] = it.next();
109			// Trim if overallocated; expand if underallocated
110			if (i < r.length \|\| it.hasNext())
111			return resizeAndFinishToArray(r, i, it);
112			return r;
113			}
114
115			/**
116			* {@inheritDoc}
117			*
118			* <p>This implementation checks if the array is large enough to contain the
119			* collection; if not, it allocates a new array of the correct size and
120			* type (using reflection). Then, it iterates over the collection,
121			* storing each object reference in the next consecutive element of the
122			* array, starting with element 0. If the array is larger than the
123			* collection, a <tt>null</tt> is stored in the first location after the
124			* end of the collection.
125			*
126			* @throws ArrayStoreException {@inheritDoc}
127			* @throws NullPointerException {@inheritDoc}
128			*/
129			public <T> T[] toArray(T[] a) {
130			// Estimate size of array; be prepared to see more or fewer elements
131			int size = size();
132			T[] r = a.length >= size? a :
133			(T[])java.lang.reflect.Array
134			.newInstance(a.getClass().getComponentType(), size);
135			int i = 0;
136			Iterator it = iterator();
137	jsr166	1.2	while (i < r.length && it.hasNext())
138	dl	1.1	r[i++] = (T)it.next();
139			// Trim if overallocated; expand if underallocated
140			if (it.hasNext() \|\| (r != a && i < r.length))
141			return resizeAndFinishToArray(r, i, it);
142	jsr166	1.2	if (i < r.length)
143	dl	1.1	r[i] = null; // null-terminate if provided array is too big
144			return r;
145			}
146
147			/**
148			* Reallocate the array being used within toArray that has a
149			* different number of elements than expected, and finish filling
150			* it if necessary
151			* @param r the array
152			* @param i the next array index to fill
153			* @param it the in-progress iterator over the collection
154			* @return larger array containing same elements
155			*/
156			private static <T> T[] resizeAndFinishToArray(T[] r, int i, Iterator it) {
157	jsr166	1.2	while (it.hasNext()) {
158	dl	1.1	int cap = r.length;
159			if (i < cap)
160			r[i++] = (T)it.next();
161			else if (cap < Integer.MAX_VALUE) { // expand
162			int newCap = (cap * 3) / 2 + 1;
163			if (newCap <= cap) // integer overflow
164			newCap = Integer.MAX_VALUE;
165			r = Arrays.copyOf(r, newCap);
166			} else // can't expand
167			throw new OutOfMemoryError("Required array size too large");
168			}
169			// trim if overallocated
170	jsr166	1.2	return i == r.length? r : Arrays.copyOf(r, i);
171	dl	1.1	}
172
173			// Modification Operations
174
175			/**
176			* {@inheritDoc}
177			*
178			* <p>This implementation always throws an
179			* <tt>UnsupportedOperationException</tt>.
180			*
181			* @throws UnsupportedOperationException {@inheritDoc}
182			* @throws ClassCastException {@inheritDoc}
183			* @throws NullPointerException {@inheritDoc}
184			* @throws IllegalArgumentException {@inheritDoc}
185			* @throws IllegalStateException {@inheritDoc}
186			*/
187			public boolean add(E e) {
188			throw new UnsupportedOperationException();
189			}
190
191			/**
192			* {@inheritDoc}
193			*
194			* <p>This implementation iterates over the collection looking for the
195			* specified element. If it finds the element, it removes the element
196			* from the collection using the iterator's remove method.
197			*
198			* <p>Note that this implementation throws an
199			* <tt>UnsupportedOperationException</tt> if the iterator returned by this
200			* collection's iterator method does not implement the <tt>remove</tt>
201			* method and this collection contains the specified object.
202			*
203			* @throws UnsupportedOperationException {@inheritDoc}
204			* @throws ClassCastException {@inheritDoc}
205			* @throws NullPointerException {@inheritDoc}
206			*/
207			public boolean remove(Object o) {
208			Iterator<E> e = iterator();
209			if (o==null) {
210			while (e.hasNext()) {
211			if (e.next()==null) {
212			e.remove();
213			return true;
214			}
215			}
216			} else {
217			while (e.hasNext()) {
218			if (o.equals(e.next())) {
219			e.remove();
220			return true;
221			}
222			}
223			}
224			return false;
225			}
226
227
228			// Bulk Operations
229
230			/**
231			* {@inheritDoc}
232			*
233			* <p>This implementation iterates over the specified collection,
234			* checking each element returned by the iterator in turn to see
235			* if it's contained in this collection. If all elements are so
236			* contained <tt>true</tt> is returned, otherwise <tt>false</tt>.
237			*
238			* @throws ClassCastException {@inheritDoc}
239			* @throws NullPointerException {@inheritDoc}
240			* @see #contains(Object)
241			*/
242			public boolean containsAll(Collection<?> c) {
243			Iterator<?> e = c.iterator();
244			while (e.hasNext())
245			if (!contains(e.next()))
246			return false;
247			return true;
248			}
249
250			/**
251			* {@inheritDoc}
252			*
253			* <p>This implementation iterates over the specified collection, and adds
254			* each object returned by the iterator to this collection, in turn.
255			*
256			* <p>Note that this implementation will throw an
257			* <tt>UnsupportedOperationException</tt> unless <tt>add</tt> is
258			* overridden (assuming the specified collection is non-empty).
259			*
260			* @throws UnsupportedOperationException {@inheritDoc}
261			* @throws ClassCastException {@inheritDoc}
262			* @throws NullPointerException {@inheritDoc}
263			* @throws IllegalArgumentException {@inheritDoc}
264			* @throws IllegalStateException {@inheritDoc}
265			*
266			* @see #add(Object)
267			*/
268			public boolean addAll(Collection<? extends E> c) {
269			boolean modified = false;
270			Iterator<? extends E> e = c.iterator();
271			while (e.hasNext()) {
272			if (add(e.next()))
273			modified = true;
274			}
275			return modified;
276			}
277
278			/**
279			* {@inheritDoc}
280			*
281			* <p>This implementation iterates over this collection, checking each
282			* element returned by the iterator in turn to see if it's contained
283			* in the specified collection. If it's so contained, it's removed from
284			* this collection with the iterator's <tt>remove</tt> method.
285			*
286			* <p>Note that this implementation will throw an
287			* <tt>UnsupportedOperationException</tt> if the iterator returned by the
288			* <tt>iterator</tt> method does not implement the <tt>remove</tt> method
289			* and this collection contains one or more elements in common with the
290			* specified collection.
291			*
292			* @throws UnsupportedOperationException {@inheritDoc}
293			* @throws ClassCastException {@inheritDoc}
294			* @throws NullPointerException {@inheritDoc}
295			*
296			* @see #remove(Object)
297			* @see #contains(Object)
298			*/
299			public boolean removeAll(Collection<?> c) {
300			boolean modified = false;
301			Iterator<?> e = iterator();
302			while (e.hasNext()) {
303			if (c.contains(e.next())) {
304			e.remove();
305			modified = true;
306			}
307			}
308			return modified;
309			}
310
311			/**
312			* {@inheritDoc}
313			*
314			* <p>This implementation iterates over this collection, checking each
315			* element returned by the iterator in turn to see if it's contained
316			* in the specified collection. If it's not so contained, it's removed
317			* from this collection with the iterator's <tt>remove</tt> method.
318			*
319			* <p>Note that this implementation will throw an
320			* <tt>UnsupportedOperationException</tt> if the iterator returned by the
321			* <tt>iterator</tt> method does not implement the <tt>remove</tt> method
322			* and this collection contains one or more elements not present in the
323			* specified collection.
324			*
325			* @throws UnsupportedOperationException {@inheritDoc}
326			* @throws ClassCastException {@inheritDoc}
327			* @throws NullPointerException {@inheritDoc}
328			*
329			* @see #remove(Object)
330			* @see #contains(Object)
331			*/
332			public boolean retainAll(Collection<?> c) {
333			boolean modified = false;
334			Iterator<E> e = iterator();
335			while (e.hasNext()) {
336			if (!c.contains(e.next())) {
337			e.remove();
338			modified = true;
339			}
340			}
341			return modified;
342			}
343
344			/**
345			* {@inheritDoc}
346			*
347			* <p>This implementation iterates over this collection, removing each
348			* element using the <tt>Iterator.remove</tt> operation. Most
349			* implementations will probably choose to override this method for
350			* efficiency.
351			*
352			* <p>Note that this implementation will throw an
353			* <tt>UnsupportedOperationException</tt> if the iterator returned by this
354			* collection's <tt>iterator</tt> method does not implement the
355			* <tt>remove</tt> method and this collection is non-empty.
356			*
357			* @throws UnsupportedOperationException {@inheritDoc}
358			*/
359			public void clear() {
360			Iterator<E> e = iterator();
361			while (e.hasNext()) {
362			e.next();
363			e.remove();
364			}
365			}
366
367
368			// String conversion
369
370			/**
371			* Returns a string representation of this collection. The string
372			* representation consists of a list of the collection's elements in the
373			* order they are returned by its iterator, enclosed in square brackets
374			* (<tt>"[]"</tt>). Adjacent elements are separated by the characters
375			* <tt>", "</tt> (comma and space). Elements are converted to strings as
376			* by {@link String#valueOf(Object)}.
377			*
378			* @return a string representation of this collection
379			*/
380			public String toString() {
381			Iterator<E> i = iterator();
382			if (! i.hasNext())
383			return "[]";
384
385			StringBuilder sb = new StringBuilder();
386			sb.append('[');
387			for (;;) {
388			E e = i.next();
389			sb.append(e == this ? "(this Collection)" : e);
390			if (! i.hasNext())
391			return sb.append(']').toString();
392			sb.append(", ");
393			}
394			}
395
396			}