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Comparing jsr166/src/main/java/util/concurrent/ConcurrentHashMap.java (file contents):
Revision 1.22 by dl, Sun Aug 31 13:33:13 2003 UTC vs.
Revision 1.52 by dl, Mon Jul 12 11:01:14 2004 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3	<	* Expert Group and released to the public domain. Use, modify, and
4	<	* redistribute this code in any way without acknowledgement.
3	>	* Expert Group and released to the public domain, as explained at
4	>	* http://creativecommons.org/licenses/publicdomain
5		*/
6
7		package java.util.concurrent;
#	Line 17 | Line 17 | import java.io.ObjectOutputStream;
17		* adjustable expected concurrency for updates. This class obeys the
18		* same functional specification as {@link java.util.Hashtable}, and
19		* includes versions of methods corresponding to each method of
20	<	* <tt>Hashtable</tt> . However, even though all operations are
20	>	* <tt>Hashtable</tt>. However, even though all operations are
21		* thread-safe, retrieval operations do <em>not</em> entail locking,
22		* and there is <em>not</em> any support for locking the entire table
23		* in a way that prevents all access.  This class is fully
24		* interoperable with <tt>Hashtable</tt> in programs that rely on its
25		* thread safety but not on its synchronization details.
26		*
27	<	* <p> Retrieval operations (including <tt>get</tt>) ordinarily
28	<	* overlap with update operations (including <tt>put</tt> and
29	<	* <tt>remove</tt>). Retrievals reflect the results of the most
30	<	* recently <em>completed</em> update operations holding upon their
31	<	* onset.  For aggregate operations such as <tt>putAll</tt> and
32	<	* <tt>clear</tt>, concurrent retrievals may reflect insertion or
27	>	* <p> Retrieval operations (including <tt>get</tt>) generally do not
28	>	* block, so may overlap with update operations (including
29	>	* <tt>put</tt> and <tt>remove</tt>). Retrievals reflect the results
30	>	* of the most recently <em>completed</em> update operations holding
31	>	* upon their onset.  For aggregate operations such as <tt>putAll</tt>
32	>	* and <tt>clear</tt>, concurrent retrievals may reflect insertion or
33		* removal of only some entries.  Similarly, Iterators and
34		* Enumerations return elements reflecting the state of the hash table
35		* at some point at or since the creation of the iterator/enumeration.
36	<	* They do <em>not</em> throw <tt>ConcurrentModificationException</tt>.
37	<	* However, Iterators are designed to be used by only one thread at a
38	<	* time.
36	>	* They do <em>not</em> throw
37	>	* {@link ConcurrentModificationException}.  However, iterators are
38	>	* designed to be used by only one thread at a time.
39		*
40		* <p> The allowed concurrency among update operations is guided by
41		* the optional <tt>concurrencyLevel</tt> constructor argument
#	Line 44 | Line 44 | import java.io.ObjectOutputStream;
44		* number of concurrent updates without contention. Because placement
45		* in hash tables is essentially random, the actual concurrency will
46		* vary.  Ideally, you should choose a value to accommodate as many
47	<	* threads as will ever concurrently access the table. Using a
47	>	* threads as will ever concurrently modify the table. Using a
48		* significantly higher value than you need can waste space and time,
49		* and a significantly lower value can lead to thread contention. But
50		* overestimates and underestimates within an order of magnitude do
51	<	* not usually have much noticeable impact.
51	>	* not usually have much noticeable impact. A value of one is
52	>	* appropriate when it is known that only one thread will modify and
53	>	* all others will only read. Also, resizing this or any other kind of
54	>	* hash table is a relatively slow operation, so, when possible, it is
55	>	* a good idea to provide estimates of expected table sizes in
56	>	* constructors.
57	>	*
58	>	* <p>This class and its views and iterators implement all of the
59	>	* <em>optional</em> methods of the {@link Map} and {@link Iterator}
60	>	* interfaces.
61		*
62		* <p> Like {@link java.util.Hashtable} but unlike {@link
63		* java.util.HashMap}, this class does NOT allow <tt>null</tt> to be
64		* used as a key or value.
65		*
66	+	* <p>This class is a member of the
67	+	* <a href="{@docRoot}/../guide/collections/index.html">
68	+	* Java Collections Framework</a>.
69	+	*
70		* @since 1.5
71		* @author Doug Lea
72	+	* @param <K> the type of keys maintained by this map
73	+	* @param <V> the type of mapped values
74		*/
75		public class ConcurrentHashMap<K, V> extends AbstractMap<K, V>
76	<	implements ConcurrentMap<K, V>, Cloneable, Serializable {
76	>	implements ConcurrentMap<K, V>, Serializable {
77		private static final long serialVersionUID = 7249069246763182397L;
78
79		/*
#	Line 72 | Line 87 | public class ConcurrentHashMap<K, V> ext
87		* The default initial number of table slots for this table.
88		* Used when not otherwise specified in constructor.
89		*/
90	<	private static int DEFAULT_INITIAL_CAPACITY = 16;
90	>	static int DEFAULT_INITIAL_CAPACITY = 16;
91
92		/**
93		* The maximum capacity, used if a higher value is implicitly
#	Line 91 | Line 106 | public class ConcurrentHashMap<K, V> ext
106		/**
107		* The default number of concurrency control segments.
108		**/
109	<	private static final int DEFAULT_SEGMENTS = 16;
109	>	static final int DEFAULT_SEGMENTS = 16;
110	>
111	>	/**
112	>	* The maximum number of segments to allow; used to bound
113	>	* constructor arguments.
114	>	*/
115	>	static final int MAX_SEGMENTS = 1 << 16; // slightly conservative
116
117		/**
118	<	* The maximum number of segments to allow; used to bound ctor arguments.
118	>	* Number of unsynchronized retries in size and containsValue
119	>	* methods before resorting to locking. This is used to avoid
120	>	* unbounded retries if tables undergo continuous modification
121	>	* which would make it impossible to obtain an accurate result.
122		*/
123	<	private static final int MAX_SEGMENTS = 1 << 16; // slightly conservative
123	>	static final int RETRIES_BEFORE_LOCK = 2;
124
125		/* ---------------- Fields -------------- */
126
#	Line 104 | Line 128 | public class ConcurrentHashMap<K, V> ext
128		* Mask value for indexing into segments. The upper bits of a
129		* key's hash code are used to choose the segment.
130		**/
131	<	private final int segmentMask;
131	>	final int segmentMask;
132
133		/**
134		* Shift value for indexing within segments.
135		**/
136	<	private final int segmentShift;
136	>	final int segmentShift;
137
138		/**
139		* The segments, each of which is a specialized hash table
140		*/
141	<	private final Segment[] segments;
141	>	final Segment[] segments;
142
143	<	private transient Set<K> keySet;
144	<	private transient Set<Map.Entry<K,V>> entrySet;
145	<	private transient Collection<V> values;
143	>	transient Set<K> keySet;
144	>	transient Set<Map.Entry<K,V>> entrySet;
145	>	transient Collection<V> values;
146
147		/* ---------------- Small Utilities -------------- */
148
149		/**
150	<	* Return a hash code for non-null Object x.
151	<	* Uses the same hash code spreader as most other j.u hash tables.
150	>	* Returns a hash code for non-null Object x.
151	>	* Uses the same hash code spreader as most other java.util hash tables.
152		* @param x the object serving as a key
153		* @return the hash code
154		*/
155	<	private static int hash(Object x) {
155	>	static int hash(Object x) {
156		int h = x.hashCode();
157		h += ~(h << 9);
158		h ^=  (h >>> 14);
#	Line 138 | Line 162 | public class ConcurrentHashMap<K, V> ext
162		}
163
164		/**
165	<	* Return the segment that should be used for key with given hash
165	>	* Returns the segment that should be used for key with given hash
166	>	* @param hash the hash code for the key
167	>	* @return the segment
168		*/
169	<	private Segment<K,V> segmentFor(int hash) {
169	>	final Segment<K,V> segmentFor(int hash) {
170		return (Segment<K,V>) segments[(hash >>> segmentShift) & segmentMask];
171		}
172
173		/* ---------------- Inner Classes -------------- */
174
175		/**
176	+	* ConcurrentHashMap list entry. Note that this is never exported
177	+	* out as a user-visible Map.Entry.
178	+	*
179	+	* Because the value field is volatile, not final, it is legal wrt
180	+	* the Java Memory Model for an unsynchronized reader to see null
181	+	* instead of initial value when read via a data race.  Although a
182	+	* reordering leading to this is not likely to ever actually
183	+	* occur, the Segment.readValueUnderLock method is used as a
184	+	* backup in case a null (pre-initialized) value is ever seen in
185	+	* an unsynchronized access method.
186	+	*/
187	+	static final class HashEntry<K,V> {
188	+	final K key;
189	+	final int hash;
190	+	volatile V value;
191	+	final HashEntry<K,V> next;
192	+
193	+	HashEntry(K key, int hash, HashEntry<K,V> next, V value) {
194	+	this.key = key;
195	+	this.hash = hash;
196	+	this.next = next;
197	+	this.value = value;
198	+	}
199	+	}
200	+
201	+	/**
202		* Segments are specialized versions of hash tables.  This
203		* subclasses from ReentrantLock opportunistically, just to
204		* simplify some locking and avoid separate construction.
205		**/
206	<	private static final class Segment<K,V> extends ReentrantLock implements Serializable {
206	>	static final class Segment<K,V> extends ReentrantLock implements Serializable {
207		/*
208		* Segments maintain a table of entry lists that are ALWAYS
209		* kept in a consistent state, so can be read without locking.
#	Line 164 | Line 216 | public class ConcurrentHashMap<K, V> ext
216		* is less than two for the default load factor threshold.)
217		*
218		* Read operations can thus proceed without locking, but rely
219	<	* on a memory barrier to ensure that completed write
220	<	* operations performed by other threads are
221	<	* noticed. Conveniently, the "count" field, tracking the
222	<	* number of elements, can also serve as the volatile variable
223	<	* providing proper read/write barriers. This is convenient
224	<	* because this field needs to be read in many read operations
173	<	* anyway.
174	<	*
175	<	* Implementors note. The basic rules for all this are:
219	>	* on selected uses of volatiles to ensure that completed
220	>	* write operations performed by other threads are
221	>	* noticed. For most purposes, the "count" field, tracking the
222	>	* number of elements, serves as that volatile variable
223	>	* ensuring visibility.  This is convenient because this field
224	>	* needs to be read in many read operations anyway:
225		*
226	<	*   - All unsynchronized read operations must first read the
226	>	*   - All (unsynchronized) read operations must first read the
227		*     "count" field, and should not look at table entries if
228		*     it is 0.
229		*
230	<	*   - All synchronized write operations should write to
231	<	*     the "count" field after updating. The operations must not
232	<	*     take any action that could even momentarily cause
233	<	*     a concurrent read operation to see inconsistent
234	<	*     data. This is made easier by the nature of the read
235	<	*     operations in Map. For example, no operation
230	>	*   - All (synchronized) write operations should write to
231	>	*     the "count" field after structurally changing any bin.
232	>	*     The operations must not take any action that could even
233	>	*     momentarily cause a concurrent read operation to see
234	>	*     inconsistent data. This is made easier by the nature of
235	>	*     the read operations in Map. For example, no operation
236		*     can reveal that the table has grown but the threshold
237		*     has not yet been updated, so there are no atomicity
238		*     requirements for this with respect to reads.
239		*
240	<	* As a guide, all critical volatile reads and writes are marked
241	<	* in code comments.
240	>	* As a guide, all critical volatile reads and writes to the
241	>	* count field are marked in code comments.
242		*/
243
244	+	private static final long serialVersionUID = 2249069246763182397L;
245	+
246		/**
247		* The number of elements in this segment's region.
248		**/
249		transient volatile int count;
250
251		/**
252	<	* Number of updates; used for checking lack of modifications
253	<	* in bulk-read methods.
252	>	* Number of updates that alter the size of the table. This is
253	>	* used during bulk-read methods to make sure they see a
254	>	* consistent snapshot: If modCounts change during a traversal
255	>	* of segments computing size or checking containsValue, then
256	>	* we might have an inconsistent view of state so (usually)
257	>	* must retry.
258		*/
259		transient int modCount;
260
#	Line 208 | Line 263 | public class ConcurrentHashMap<K, V> ext
263		* (The value of this field is always (int)(capacity *
264		* loadFactor).)
265		*/
266	<	private transient int threshold;
266	>	transient int threshold;
267
268		/**
269	<	* The per-segment table
269	>	* The per-segment table. Declared as a raw type, casted
270	>	* to HashEntry<K,V> on each use.
271		*/
272	<	transient HashEntry[] table;
272	>	transient volatile HashEntry[] table;
273
274		/**
275		* The load factor for the hash table.  Even though this value
#	Line 221 | Line 277 | public class ConcurrentHashMap<K, V> ext
277		* links to outer object.
278		* @serial
279		*/
280	<	private final float loadFactor;
280	>	final float loadFactor;
281
282		Segment(int initialCapacity, float lf) {
283		loadFactor = lf;
#	Line 232 | Line 288 | public class ConcurrentHashMap<K, V> ext
288		* Set table to new HashEntry array.
289		* Call only while holding lock or in constructor.
290		**/
291	<	private void setTable(HashEntry[] newTable) {
236	<	table = newTable;
291	>	void setTable(HashEntry[] newTable) {
292		threshold = (int)(newTable.length * loadFactor);
293	<	count = count; // write-volatile
293	>	table = newTable;
294	>	}
295	>
296	>	/**
297	>	* Return properly casted first entry of bin for given hash
298	>	*/
299	>	HashEntry<K,V> getFirst(int hash) {
300	>	HashEntry[] tab = table;
301	>	return (HashEntry<K,V>) tab[hash & (tab.length - 1)];
302	>	}
303	>
304	>	/**
305	>	* Read value field of an entry under lock. Called if value
306	>	* field ever appears to be null. This is possible only if a
307	>	* compiler happens to reorder a HashEntry initialization with
308	>	* its table assignment, which is legal under memory model
309	>	* but is not known to ever occur.
310	>	*/
311	>	V readValueUnderLock(HashEntry<K,V> e) {
312	>	lock();
313	>	try {
314	>	return e.value;
315	>	} finally {
316	>	unlock();
317	>	}
318		}
319
320		/* Specialized implementations of map methods */
321
322	<	V get(K key, int hash) {
322	>	V get(Object key, int hash) {
323		if (count != 0) { // read-volatile
324	<	HashEntry[] tab = table;
246	<	int index = hash & (tab.length - 1);
247	<	HashEntry<K,V> e = (HashEntry<K,V>) tab[index];
324	>	HashEntry<K,V> e = getFirst(hash);
325		while (e != null) {
326	<	if (e.hash == hash && key.equals(e.key))
327	<	return e.value;
326	>	if (e.hash == hash && key.equals(e.key)) {
327	>	V v = e.value;
328	>	if (v != null)
329	>	return v;
330	>	return readValueUnderLock(e); // recheck
331	>	}
332		e = e.next;
333		}
334		}
#	Line 256 | Line 337 | public class ConcurrentHashMap<K, V> ext
337
338		boolean containsKey(Object key, int hash) {
339		if (count != 0) { // read-volatile
340	<	HashEntry[] tab = table;
260	<	int index = hash & (tab.length - 1);
261	<	HashEntry<K,V> e = (HashEntry<K,V>) tab[index];
340	>	HashEntry<K,V> e = getFirst(hash);
341		while (e != null) {
342		if (e.hash == hash && key.equals(e.key))
343		return true;
#	Line 272 | Line 351 | public class ConcurrentHashMap<K, V> ext
351		if (count != 0) { // read-volatile
352		HashEntry[] tab = table;
353		int len = tab.length;
354	<	for (int i = 0 ; i < len; i++)
355	<	for (HashEntry<K,V> e = (HashEntry<K,V>)tab[i] ; e != null ; e = e.next)
356	<	if (value.equals(e.value))
354	>	for (int i = 0 ; i < len; i++) {
355	>	for (HashEntry<K,V> e = (HashEntry<K,V>)tab[i];
356	>	e != null ;
357	>	e = e.next) {
358	>	V v = e.value;
359	>	if (v == null) // recheck
360	>	v = readValueUnderLock(e);
361	>	if (value.equals(v))
362		return true;
363	+	}
364	+	}
365		}
366		return false;
367		}
368
369	+	boolean replace(K key, int hash, V oldValue, V newValue) {
370	+	lock();
371	+	try {
372	+	HashEntry<K,V> e = getFirst(hash);
373	+	while (e != null && (e.hash != hash || !key.equals(e.key)))
374	+	e = e.next;
375	+
376	+	boolean replaced = false;
377	+	if (e != null && oldValue.equals(e.value)) {
378	+	replaced = true;
379	+	e.value = newValue;
380	+	}
381	+	return replaced;
382	+	} finally {
383	+	unlock();
384	+	}
385	+	}
386	+
387	+	V replace(K key, int hash, V newValue) {
388	+	lock();
389	+	try {
390	+	HashEntry<K,V> e = getFirst(hash);
391	+	while (e != null && (e.hash != hash || !key.equals(e.key)))
392	+	e = e.next;
393	+
394	+	V oldValue = null;
395	+	if (e != null) {
396	+	oldValue = e.value;
397	+	e.value = newValue;
398	+	}
399	+	return oldValue;
400	+	} finally {
401	+	unlock();
402	+	}
403	+	}
404	+
405	+
406		V put(K key, int hash, V value, boolean onlyIfAbsent) {
407		lock();
408		try {
409		int c = count;
410	+	if (c++ > threshold) // ensure capacity
411	+	rehash();
412		HashEntry[] tab = table;
413		int index = hash & (tab.length - 1);
414		HashEntry<K,V> first = (HashEntry<K,V>) tab[index];
415	+	HashEntry<K,V> e = first;
416	+	while (e != null && (e.hash != hash || !key.equals(e.key)))
417	+	e = e.next;
418
419	<	for (HashEntry<K,V> e = first; e != null; e = (HashEntry<K,V>) e.next) {
420	<	if (e.hash == hash && key.equals(e.key)) {
421	<	V oldValue = e.value;
422	<	if (!onlyIfAbsent)
423	<	e.value = value;
296	<	++modCount;
297	<	count = c; // write-volatile
298	<	return oldValue;
299	<	}
419	>	V oldValue;
420	>	if (e != null) {
421	>	oldValue = e.value;
422	>	if (!onlyIfAbsent)
423	>	e.value = value;
424		}
425	<
426	<	tab[index] = new HashEntry<K,V>(hash, key, value, first);
427	<	++modCount;
428	<	++c;
429	<	count = c; // write-volatile
430	<	if (c > threshold)
431	<	setTable(rehash(tab));
308	<	return null;
425	>	else {
426	>	oldValue = null;
427	>	++modCount;
428	>	tab[index] = new HashEntry<K,V>(key, hash, first, value);
429	>	count = c; // write-volatile
430	>	}
431	>	return oldValue;
432		} finally {
433		unlock();
434		}
435		}
436
437	<	private HashEntry[] rehash(HashEntry[] oldTable) {
437	>	void rehash() {
438	>	HashEntry[] oldTable = table;
439		int oldCapacity = oldTable.length;
440		if (oldCapacity >= MAXIMUM_CAPACITY)
441	<	return oldTable;
441	>	return;
442
443		/*
444		* Reclassify nodes in each list to new Map.  Because we are
#	Line 323 | Line 447 | public class ConcurrentHashMap<K, V> ext
447		* offset. We eliminate unnecessary node creation by catching
448		* cases where old nodes can be reused because their next
449		* fields won't change. Statistically, at the default
450	<	* threshhold, only about one-sixth of them need cloning when
450	>	* threshold, only about one-sixth of them need cloning when
451		* a table doubles. The nodes they replace will be garbage
452		* collectable as soon as they are no longer referenced by any
453		* reader thread that may be in the midst of traversing table
#	Line 331 | Line 455 | public class ConcurrentHashMap<K, V> ext
455		*/
456
457		HashEntry[] newTable = new HashEntry[oldCapacity << 1];
458	+	threshold = (int)(newTable.length * loadFactor);
459		int sizeMask = newTable.length - 1;
460		for (int i = 0; i < oldCapacity ; i++) {
461		// We need to guarantee that any existing reads of old Map can
#	Line 363 | Line 488 | public class ConcurrentHashMap<K, V> ext
488		// Clone all remaining nodes
489		for (HashEntry<K,V> p = e; p != lastRun; p = p.next) {
490		int k = p.hash & sizeMask;
491	<	newTable[k] = new HashEntry<K,V>(p.hash,
492	<	p.key,
493	<	p.value,
369	<	(HashEntry<K,V>) newTable[k]);
491	>	HashEntry<K,V> n = (HashEntry<K,V>)newTable[k];
492	>	newTable[k] = new HashEntry<K,V>(p.key, p.hash,
493	>	n, p.value);
494		}
495		}
496		}
497		}
498	<	return newTable;
498	>	table = newTable;
499		}
500
501		/**
#	Line 380 | Line 504 | public class ConcurrentHashMap<K, V> ext
504		V remove(Object key, int hash, Object value) {
505		lock();
506		try {
507	<	int c = count;
507	>	int c = count - 1;
508		HashEntry[] tab = table;
509		int index = hash & (tab.length - 1);
510		HashEntry<K,V> first = (HashEntry<K,V>)tab[index];
387	–
511		HashEntry<K,V> e = first;
512	<	for (;;) {
390	<	if (e == null)
391	<	return null;
392	<	if (e.hash == hash && key.equals(e.key))
393	<	break;
512	>	while (e != null && (e.hash != hash || !key.equals(e.key)))
513		e = e.next;
395	–	}
514
515	<	V oldValue = e.value;
516	<	if (value != null && !value.equals(oldValue))
517	<	return null;
518	<
519	<	// All entries following removed node can stay in list, but
520	<	// all preceeding ones need to be cloned.
521	<	HashEntry<K,V> newFirst = e.next;
522	<	for (HashEntry<K,V> p = first; p != e; p = p.next)
523	<	newFirst = new HashEntry<K,V>(p.hash, p.key,
524	<	p.value, newFirst);
525	<	tab[index] = newFirst;
526	<	++modCount;
527	<	count = c-1; // write-volatile
515	>	V oldValue = null;
516	>	if (e != null) {
517	>	V v = e.value;
518	>	if (value == null || value.equals(v)) {
519	>	oldValue = v;
520	>	// All entries following removed node can stay
521	>	// in list, but all preceding ones need to be
522	>	// cloned.
523	>	++modCount;
524	>	HashEntry<K,V> newFirst = e.next;
525	>	for (HashEntry<K,V> p = first; p != e; p = p.next)
526	>	newFirst = new HashEntry<K,V>(p.key, p.hash,
527	>	newFirst, p.value);
528	>	tab[index] = newFirst;
529	>	count = c; // write-volatile
530	>	}
531	>	}
532		return oldValue;
533		} finally {
534		unlock();
#	Line 414 | Line 536 | public class ConcurrentHashMap<K, V> ext
536		}
537
538		void clear() {
539	<	lock();
540	<	try {
541	<	HashEntry[] tab = table;
542	<	for (int i = 0; i < tab.length ; i++)
543	<	tab[i] = null;
544	<	++modCount;
545	<	count = 0; // write-volatile
546	<	} finally {
547	<	unlock();
539	>	if (count != 0) {
540	>	lock();
541	>	try {
542	>	HashEntry[] tab = table;
543	>	for (int i = 0; i < tab.length ; i++)
544	>	tab[i] = null;
545	>	++modCount;
546	>	count = 0; // write-volatile
547	>	} finally {
548	>	unlock();
549	>	}
550		}
551		}
552		}
553
430	–	/**
431	–	* ConcurrentHashMap list entry.
432	–	*/
433	–	private static class HashEntry<K,V> implements Entry<K,V> {
434	–	private final K key;
435	–	private V value;
436	–	private final int hash;
437	–	private final HashEntry<K,V> next;
438	–
439	–	HashEntry(int hash, K key, V value, HashEntry<K,V> next) {
440	–	this.value = value;
441	–	this.hash = hash;
442	–	this.key = key;
443	–	this.next = next;
444	–	}
445	–
446	–	public K getKey() {
447	–	return key;
448	–	}
449	–
450	–	public V getValue() {
451	–	return value;
452	–	}
453	–
454	–	public V setValue(V newValue) {
455	–	// We aren't required to, and don't provide any
456	–	// visibility barriers for setting value.
457	–	if (newValue == null)
458	–	throw new NullPointerException();
459	–	V oldValue = this.value;
460	–	this.value = newValue;
461	–	return oldValue;
462	–	}
463	–
464	–	public boolean equals(Object o) {
465	–	if (!(o instanceof Entry))
466	–	return false;
467	–	Entry<K,V> e = (Entry<K,V>)o;
468	–	return (key.equals(e.getKey()) && value.equals(e.getValue()));
469	–	}
470	–
471	–	public int hashCode() {
472	–	return  key.hashCode() ^ value.hashCode();
473	–	}
474	–
475	–	public String toString() {
476	–	return key + "=" + value;
477	–	}
478	–	}
554
555
556		/* ---------------- Public operations -------------- */
557
558		/**
559	<	* Constructs a new, empty map with the specified initial
560	<	* capacity and the specified load factor.
559	>	* Creates a new, empty map with the specified initial
560	>	* capacity, load factor, and concurrency level.
561		*
562		* @param initialCapacity the initial capacity. The implementation
563		* performs internal sizing to accommodate this many elements.
564		* @param loadFactor  the load factor threshold, used to control resizing.
565	+	* Resizing may be performed when the average number of elements per
566	+	* bin exceeds this threshold.
567		* @param concurrencyLevel the estimated number of concurrently
568		* updating threads. The implementation performs internal sizing
569		* to try to accommodate this many threads.
#	Line 527 | Line 604 | public class ConcurrentHashMap<K, V> ext
604		}
605
606		/**
607	<	* Constructs a new, empty map with the specified initial
608	<	* capacity,  and with default load factor and concurrencyLevel.
607	>	* Creates a new, empty map with the specified initial
608	>	* capacity,  and with default load factor (<tt>0.75f</tt>)
609	>	* and concurrencyLevel (<tt>16</tt>).
610		*
611	<	* @param initialCapacity The implementation performs internal
612	<	* sizing to accommodate this many elements.
611	>	* @param initialCapacity the initial capacity. The implementation
612	>	* performs internal sizing to accommodate this many elements.
613		* @throws IllegalArgumentException if the initial capacity of
614		* elements is negative.
615		*/
#	Line 540 | Line 618 | public class ConcurrentHashMap<K, V> ext
618		}
619
620		/**
621	<	* Constructs a new, empty map with a default initial capacity,
622	<	* load factor, and number of concurrencyLevel.
621	>	* Creates a new, empty map with a default initial capacity
622	>	* (<tt>16</tt>), load factor (<tt>0.75f</tt>) and
623	>	* concurrencyLevel (<tt>16</tt>).
624		*/
625		public ConcurrentHashMap() {
626		this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_SEGMENTS);
627		}
628
629		/**
630	<	* Constructs a new map with the same mappings as the given map.  The
631	<	* map is created with a capacity of twice the number of mappings in
632	<	* the given map or 11 (whichever is greater), and a default load factor.
630	>	* Creates a new map with the same mappings as the given map.  The
631	>	* map is created with a capacity consistent with the default load
632	>	* factor (<tt>0.75f</tt>) and uses the default concurrencyLevel
633	>	* (<tt>16</tt>).
634	>	* @param t the map
635		*/
636	<	public <A extends K, B extends V> ConcurrentHashMap(Map<A,B> t) {
636	>	public ConcurrentHashMap(Map<? extends K, ? extends V> t) {
637		this(Math.max((int) (t.size() / DEFAULT_LOAD_FACTOR) + 1,
638	<	11),
638	>	DEFAULT_INITIAL_CAPACITY),
639		DEFAULT_LOAD_FACTOR, DEFAULT_SEGMENTS);
640		putAll(t);
641		}
642
643		// inherit Map javadoc
644		public boolean isEmpty() {
645	+	final Segment[] segments = this.segments;
646		/*
647	<	* We need to keep track of per-segment modCounts to avoid ABA
647	>	* We keep track of per-segment modCounts to avoid ABA
648		* problems in which an element in one segment was added and
649		* in another removed during traversal, in which case the
650		* table was never actually empty at any point. Note the
#	Line 593 | Line 675 | public class ConcurrentHashMap<K, V> ext
675
676		// inherit Map javadoc
677		public int size() {
678	+	final Segment[] segments = this.segments;
679	+	long sum = 0;
680	+	long check = 0;
681		int[] mc = new int[segments.length];
682	<	for (;;) {
683	<	int sum = 0;
682	>	// Try a few times to get accurate count. On failure due to
683	>	// continuous async changes in table, resort to locking.
684	>	for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) {
685	>	check = 0;
686	>	sum = 0;
687		int mcsum = 0;
688		for (int i = 0; i < segments.length; ++i) {
689		sum += segments[i].count;
690		mcsum += mc[i] = segments[i].modCount;
691		}
604	–	int check = 0;
692		if (mcsum != 0) {
693		for (int i = 0; i < segments.length; ++i) {
694		check += segments[i].count;
#	Line 611 | Line 698 | public class ConcurrentHashMap<K, V> ext
698		}
699		}
700		}
701	<	if (check == sum)
702	<	return sum;
701	>	if (check == sum)
702	>	break;
703	>	}
704	>	if (check != sum) { // Resort to locking all segments
705	>	sum = 0;
706	>	for (int i = 0; i < segments.length; ++i)
707	>	segments[i].lock();
708	>	for (int i = 0; i < segments.length; ++i)
709	>	sum += segments[i].count;
710	>	for (int i = 0; i < segments.length; ++i)
711	>	segments[i].unlock();
712		}
713	+	if (sum > Integer.MAX_VALUE)
714	+	return Integer.MAX_VALUE;
715	+	else
716	+	return (int)sum;
717		}
718
719
#	Line 626 | Line 726 | public class ConcurrentHashMap<K, V> ext
726		*          this table.
727		* @throws  NullPointerException  if the key is
728		*               <tt>null</tt>.
629	–	* @see     #put(Object, Object)
729		*/
730		public V get(Object key) {
731		int hash = hash(key); // throws NullPointerException if key null
732	<	return segmentFor(hash).get((K) key, hash);
732	>	return segmentFor(hash).get(key, hash);
733		}
734
735		/**
#	Line 642 | Line 741 | public class ConcurrentHashMap<K, V> ext
741		*          <tt>equals</tt> method; <tt>false</tt> otherwise.
742		* @throws  NullPointerException  if the key is
743		*               <tt>null</tt>.
645	–	* @see     #contains(Object)
744		*/
745		public boolean containsKey(Object key) {
746		int hash = hash(key); // throws NullPointerException if key null
#	Line 663 | Line 761 | public class ConcurrentHashMap<K, V> ext
761		public boolean containsValue(Object value) {
762		if (value == null)
763		throw new NullPointerException();
764	+
765	+	// See explanation of modCount use above
766
767	+	final Segment[] segments = this.segments;
768		int[] mc = new int[segments.length];
769	<	for (;;) {
769	>
770	>	// Try a few times without locking
771	>	for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) {
772		int sum = 0;
773		int mcsum = 0;
774		for (int i = 0; i < segments.length; ++i) {
#	Line 687 | Line 790 | public class ConcurrentHashMap<K, V> ext
790		if (cleanSweep)
791		return false;
792		}
793	+	// Resort to locking all segments
794	+	for (int i = 0; i < segments.length; ++i)
795	+	segments[i].lock();
796	+	boolean found = false;
797	+	try {
798	+	for (int i = 0; i < segments.length; ++i) {
799	+	if (segments[i].containsValue(value)) {
800	+	found = true;
801	+	break;
802	+	}
803	+	}
804	+	} finally {
805	+	for (int i = 0; i < segments.length; ++i)
806	+	segments[i].unlock();
807	+	}
808	+	return found;
809		}
810
811		/**
812		* Legacy method testing if some key maps into the specified value
813	<	* in this table.  This operation is more expensive than the
814	<	* <tt>containsKey</tt> method.
696	<	*
697	<	* <p> Note that this method is identical in functionality to
698	<	* <tt>containsValue</tt>, This method exists solely to ensure
813	>	* in this table.  This method is identical in functionality to
814	>	* {@link #containsValue}, and  exists solely to ensure
815		* full compatibility with class {@link java.util.Hashtable},
816		* which supported this method prior to introduction of the
817	<	* collections framework.
817	>	* Java Collections framework.
818
819		* @param      value   a value to search for.
820		* @return     <tt>true</tt> if and only if some key maps to the
#	Line 706 | Line 822 | public class ConcurrentHashMap<K, V> ext
822		*             determined by the <tt>equals</tt> method;
823		*             <tt>false</tt> otherwise.
824		* @throws  NullPointerException  if the value is <tt>null</tt>.
709	–	* @see        #containsKey(Object)
710	–	* @see        #containsValue(Object)
711	–	* @see   Map
825		*/
826		public boolean contains(Object value) {
827		return containsValue(value);
#	Line 717 | Line 830 | public class ConcurrentHashMap<K, V> ext
830		/**
831		* Maps the specified <tt>key</tt> to the specified
832		* <tt>value</tt> in this table. Neither the key nor the
833	<	* value can be <tt>null</tt>. <p>
833	>	* value can be <tt>null</tt>.
834		*
835	<	* The value can be retrieved by calling the <tt>get</tt> method
835	>	* <p> The value can be retrieved by calling the <tt>get</tt> method
836		* with a key that is equal to the original key.
837		*
838		* @param      key     the table key.
#	Line 728 | Line 841 | public class ConcurrentHashMap<K, V> ext
841		*             or <tt>null</tt> if it did not have one.
842		* @throws  NullPointerException  if the key or value is
843		*               <tt>null</tt>.
731	–	* @see     Object#equals(Object)
732	–	* @see     #get(Object)
844		*/
845		public V put(K key, V value) {
846		if (value == null)
#	Line 752 | Line 863 | public class ConcurrentHashMap<K, V> ext
863		* @param key key with which the specified value is to be associated.
864		* @param value value to be associated with the specified key.
865		* @return previous value associated with specified key, or <tt>null</tt>
866	<	*         if there was no mapping for key.  A <tt>null</tt> return can
756	<	*         also indicate that the map previously associated <tt>null</tt>
757	<	*         with the specified key, if the implementation supports
758	<	*         <tt>null</tt> values.
759	<	*
760	<	* @throws UnsupportedOperationException if the <tt>put</tt> operation is
761	<	*            not supported by this map.
762	<	* @throws ClassCastException if the class of the specified key or value
763	<	*            prevents it from being stored in this map.
866	>	*         if there was no mapping for key.
867		* @throws NullPointerException if the specified key or value is
868		*            <tt>null</tt>.
869	<	*
767	<	**/
869	>	*/
870		public V putIfAbsent(K key, V value) {
871		if (value == null)
872		throw new NullPointerException();
#	Line 782 | Line 884 | public class ConcurrentHashMap<K, V> ext
884		* @param t Mappings to be stored in this map.
885		*/
886		public void putAll(Map<? extends K, ? extends V> t) {
887	<	Iterator<Map.Entry<? extends K, ? extends V>> it = t.entrySet().iterator();
786	<	while (it.hasNext()) {
887	>	for (Iterator<? extends Map.Entry<? extends K, ? extends V>> it = (Iterator<? extends Map.Entry<? extends K, ? extends V>>) t.entrySet().iterator(); it.hasNext(); ) {
888		Entry<? extends K, ? extends V> e = it.next();
889		put(e.getKey(), e.getValue());
890		}
#	Line 825 | Line 926 | public class ConcurrentHashMap<K, V> ext
926		return segmentFor(hash).remove(key, hash, value) != null;
927		}
928
929	+
930		/**
931	<	* Removes all mappings from this map.
931	>	* Replace entry for key only if currently mapped to given value.
932	>	* Acts as
933	>	* <pre>
934	>	*  if (map.get(key).equals(oldValue)) {
935	>	*     map.put(key, newValue);
936	>	*     return true;
937	>	* } else return false;
938	>	* </pre>
939	>	* except that the action is performed atomically.
940	>	* @param key key with which the specified value is associated.
941	>	* @param oldValue value expected to be associated with the specified key.
942	>	* @param newValue value to be associated with the specified key.
943	>	* @return true if the value was replaced
944	>	* @throws NullPointerException if the specified key or values are
945	>	* <tt>null</tt>.
946		*/
947	<	public void clear() {
948	<	for (int i = 0; i < segments.length; ++i)
949	<	segments[i].clear();
947	>	public boolean replace(K key, V oldValue, V newValue) {
948	>	if (oldValue == null || newValue == null)
949	>	throw new NullPointerException();
950	>	int hash = hash(key);
951	>	return segmentFor(hash).replace(key, hash, oldValue, newValue);
952	>	}
953	>
954	>	/**
955	>	* Replace entry for key only if currently mapped to some value.
956	>	* Acts as
957	>	* <pre>
958	>	*  if ((map.containsKey(key)) {
959	>	*     return map.put(key, value);
960	>	* } else return null;
961	>	* </pre>
962	>	* except that the action is performed atomically.
963	>	* @param key key with which the specified value is associated.
964	>	* @param value value to be associated with the specified key.
965	>	* @return previous value associated with specified key, or <tt>null</tt>
966	>	*         if there was no mapping for key.
967	>	* @throws NullPointerException if the specified key or value is
968	>	*            <tt>null</tt>.
969	>	*/
970	>	public V replace(K key, V value) {
971	>	if (value == null)
972	>	throw new NullPointerException();
973	>	int hash = hash(key);
974	>	return segmentFor(hash).replace(key, hash, value);
975		}
976
977
978		/**
979	<	* Returns a shallow copy of this
839	<	* <tt>ConcurrentHashMap</tt> instance: the keys and
840	<	* values themselves are not cloned.
841	<	*
842	<	* @return a shallow copy of this map.
979	>	* Removes all mappings from this map.
980		*/
981	<	public Object clone() {
982	<	// We cannot call super.clone, since it would share final
983	<	// segments array, and there's no way to reassign finals.
847	<
848	<	float lf = segments[0].loadFactor;
849	<	int segs = segments.length;
850	<	int cap = (int)(size() / lf);
851	<	if (cap < segs) cap = segs;
852	<	ConcurrentHashMap<K,V> t = new ConcurrentHashMap<K,V>(cap, lf, segs);
853	<	t.putAll(this);
854	<	return t;
981	>	public void clear() {
982	>	for (int i = 0; i < segments.length; ++i)
983	>	segments[i].clear();
984		}
985
986		/**
#	Line 862 | Line 991 | public class ConcurrentHashMap<K, V> ext
991		* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and
992		* <tt>clear</tt> operations.  It does not support the <tt>add</tt> or
993		* <tt>addAll</tt> operations.
994	<	* The returned <tt>iterator</tt> is a "weakly consistent" iterator that
994	>	* The view's returned <tt>iterator</tt> is a "weakly consistent" iterator that
995		* will never throw {@link java.util.ConcurrentModificationException},
996		* and guarantees to traverse elements as they existed upon
997		* construction of the iterator, and may (but is not guaranteed to)
#	Line 884 | Line 1013 | public class ConcurrentHashMap<K, V> ext
1013		* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
1014		* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
1015		* It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
1016	<	* The returned <tt>iterator</tt> is a "weakly consistent" iterator that
1016	>	* The view's returned <tt>iterator</tt> is a "weakly consistent" iterator that
1017		* will never throw {@link java.util.ConcurrentModificationException},
1018		* and guarantees to traverse elements as they existed upon
1019		* construction of the iterator, and may (but is not guaranteed to)
#	Line 907 | Line 1036 | public class ConcurrentHashMap<K, V> ext
1036		* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
1037		* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
1038		* It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
1039	<	* The returned <tt>iterator</tt> is a "weakly consistent" iterator that
1039	>	* The view's returned <tt>iterator</tt> is a "weakly consistent" iterator that
1040		* will never throw {@link java.util.ConcurrentModificationException},
1041		* and guarantees to traverse elements as they existed upon
1042		* construction of the iterator, and may (but is not guaranteed to)
#	Line 917 | Line 1046 | public class ConcurrentHashMap<K, V> ext
1046		*/
1047		public Set<Map.Entry<K,V>> entrySet() {
1048		Set<Map.Entry<K,V>> es = entrySet;
1049	<	return (es != null) ? es : (entrySet = new EntrySet());
1049	>	return (es != null) ? es : (entrySet = (Set<Map.Entry<K,V>>) (Set) new EntrySet());
1050		}
1051
1052
#	Line 925 | Line 1054 | public class ConcurrentHashMap<K, V> ext
1054		* Returns an enumeration of the keys in this table.
1055		*
1056		* @return  an enumeration of the keys in this table.
1057	<	* @see     Enumeration
929	<	* @see     #elements()
930	<	* @see     #keySet()
931	<	* @see     Map
1057	>	* @see     #keySet
1058		*/
1059		public Enumeration<K> keys() {
1060		return new KeyIterator();
#	Line 936 | Line 1062 | public class ConcurrentHashMap<K, V> ext
1062
1063		/**
1064		* Returns an enumeration of the values in this table.
939	–	* Use the Enumeration methods on the returned object to fetch the elements
940	–	* sequentially.
1065		*
1066		* @return  an enumeration of the values in this table.
1067	<	* @see     java.util.Enumeration
944	<	* @see     #keys()
945	<	* @see     #values()
946	<	* @see     Map
1067	>	* @see     #values
1068		*/
1069		public Enumeration<V> elements() {
1070		return new ValueIterator();
#	Line 951 | Line 1072 | public class ConcurrentHashMap<K, V> ext
1072
1073		/* ---------------- Iterator Support -------------- */
1074
1075	<	private abstract class HashIterator {
1076	<	private int nextSegmentIndex;
1077	<	private int nextTableIndex;
1078	<	private HashEntry[] currentTable;
1079	<	private HashEntry<K, V> nextEntry;
1080	<	private HashEntry<K, V> lastReturned;
1075	>	abstract class HashIterator {
1076	>	int nextSegmentIndex;
1077	>	int nextTableIndex;
1078	>	HashEntry[] currentTable;
1079	>	HashEntry<K, V> nextEntry;
1080	>	HashEntry<K, V> lastReturned;
1081
1082	<	private HashIterator() {
1082	>	HashIterator() {
1083		nextSegmentIndex = segments.length - 1;
1084		nextTableIndex = -1;
1085		advance();
#	Line 966 | Line 1087 | public class ConcurrentHashMap<K, V> ext
1087
1088		public boolean hasMoreElements() { return hasNext(); }
1089
1090	<	private void advance() {
1090	>	final void advance() {
1091		if (nextEntry != null && (nextEntry = nextEntry.next) != null)
1092		return;
1093
#	Line 1007 | Line 1128 | public class ConcurrentHashMap<K, V> ext
1128		}
1129		}
1130
1131	<	private class KeyIterator extends HashIterator implements Iterator<K>, Enumeration<K> {
1131	>	final class KeyIterator extends HashIterator implements Iterator<K>, Enumeration<K> {
1132		public K next() { return super.nextEntry().key; }
1133		public K nextElement() { return super.nextEntry().key; }
1134		}
1135
1136	<	private class ValueIterator extends HashIterator implements Iterator<V>, Enumeration<V> {
1136	>	final class ValueIterator extends HashIterator implements Iterator<V>, Enumeration<V> {
1137		public V next() { return super.nextEntry().value; }
1138		public V nextElement() { return super.nextEntry().value; }
1139		}
1140
1141	<	private class EntryIterator extends HashIterator implements Iterator<Entry<K,V>> {
1142	<	public Map.Entry<K,V> next() { return super.nextEntry(); }
1141	>
1142	>
1143	>	/**
1144	>	* Entry iterator. Exported Entry objects must write-through
1145	>	* changes in setValue, even if the nodes have been cloned. So we
1146	>	* cannot return internal HashEntry objects. Instead, the iterator
1147	>	* itself acts as a forwarding pseudo-entry.
1148	>	*/
1149	>	final class EntryIterator extends HashIterator implements Map.Entry<K,V>, Iterator<Entry<K,V>> {
1150	>	public Map.Entry<K,V> next() {
1151	>	nextEntry();
1152	>	return this;
1153	>	}
1154	>
1155	>	public K getKey() {
1156	>	if (lastReturned == null)
1157	>	throw new IllegalStateException("Entry was removed");
1158	>	return lastReturned.key;
1159	>	}
1160	>
1161	>	public V getValue() {
1162	>	if (lastReturned == null)
1163	>	throw new IllegalStateException("Entry was removed");
1164	>	return ConcurrentHashMap.this.get(lastReturned.key);
1165	>	}
1166	>
1167	>	public V setValue(V value) {
1168	>	if (lastReturned == null)
1169	>	throw new IllegalStateException("Entry was removed");
1170	>	return ConcurrentHashMap.this.put(lastReturned.key, value);
1171	>	}
1172	>
1173	>	public boolean equals(Object o) {
1174	>	// If not acting as entry, just use default.
1175	>	if (lastReturned == null)
1176	>	return super.equals(o);
1177	>	if (!(o instanceof Map.Entry))
1178	>	return false;
1179	>	Map.Entry e = (Map.Entry)o;
1180	>	return eq(getKey(), e.getKey()) && eq(getValue(), e.getValue());
1181	>	}
1182	>
1183	>	public int hashCode() {
1184	>	// If not acting as entry, just use default.
1185	>	if (lastReturned == null)
1186	>	return super.hashCode();
1187	>
1188	>	Object k = getKey();
1189	>	Object v = getValue();
1190	>	return ((k == null) ? 0 : k.hashCode()) ^
1191	>	((v == null) ? 0 : v.hashCode());
1192	>	}
1193	>
1194	>	public String toString() {
1195	>	// If not acting as entry, just use default.
1196	>	if (lastReturned == null)
1197	>	return super.toString();
1198	>	else
1199	>	return getKey() + "=" + getValue();
1200	>	}
1201	>
1202	>	boolean eq(Object o1, Object o2) {
1203	>	return (o1 == null ? o2 == null : o1.equals(o2));
1204	>	}
1205	>
1206		}
1207
1208	<	private class KeySet extends AbstractSet<K> {
1208	>	final class KeySet extends AbstractSet<K> {
1209		public Iterator<K> iterator() {
1210		return new KeyIterator();
1211		}
#	Line 1037 | Line 1221 | public class ConcurrentHashMap<K, V> ext
1221		public void clear() {
1222		ConcurrentHashMap.this.clear();
1223		}
1224	+	public Object[] toArray() {
1225	+	Collection<K> c = new ArrayList<K>();
1226	+	for (Iterator<K> i = iterator(); i.hasNext(); )
1227	+	c.add(i.next());
1228	+	return c.toArray();
1229	+	}
1230	+	public <T> T[] toArray(T[] a) {
1231	+	Collection<K> c = new ArrayList<K>();
1232	+	for (Iterator<K> i = iterator(); i.hasNext(); )
1233	+	c.add(i.next());
1234	+	return c.toArray(a);
1235	+	}
1236		}
1237
1238	<	private class Values extends AbstractCollection<V> {
1238	>	final class Values extends AbstractCollection<V> {
1239		public Iterator<V> iterator() {
1240		return new ValueIterator();
1241		}
#	Line 1052 | Line 1248 | public class ConcurrentHashMap<K, V> ext
1248		public void clear() {
1249		ConcurrentHashMap.this.clear();
1250		}
1251	+	public Object[] toArray() {
1252	+	Collection<V> c = new ArrayList<V>();
1253	+	for (Iterator<V> i = iterator(); i.hasNext(); )
1254	+	c.add(i.next());
1255	+	return c.toArray();
1256	+	}
1257	+	public <T> T[] toArray(T[] a) {
1258	+	Collection<V> c = new ArrayList<V>();
1259	+	for (Iterator<V> i = iterator(); i.hasNext(); )
1260	+	c.add(i.next());
1261	+	return c.toArray(a);
1262	+	}
1263		}
1264
1265	<	private class EntrySet extends AbstractSet<Map.Entry<K,V>> {
1265	>	final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
1266		public Iterator<Map.Entry<K,V>> iterator() {
1267		return new EntryIterator();
1268		}
#	Line 1077 | Line 1285 | public class ConcurrentHashMap<K, V> ext
1285		public void clear() {
1286		ConcurrentHashMap.this.clear();
1287		}
1288	+	public Object[] toArray() {
1289	+	// Since we don't ordinarily have distinct Entry objects, we
1290	+	// must pack elements using exportable SimpleEntry
1291	+	Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>(size());
1292	+	for (Iterator<Map.Entry<K,V>> i = iterator(); i.hasNext(); )
1293	+	c.add(new SimpleEntry<K,V>(i.next()));
1294	+	return c.toArray();
1295	+	}
1296	+	public <T> T[] toArray(T[] a) {
1297	+	Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>(size());
1298	+	for (Iterator<Map.Entry<K,V>> i = iterator(); i.hasNext(); )
1299	+	c.add(new SimpleEntry<K,V>(i.next()));
1300	+	return c.toArray(a);
1301	+	}
1302	+
1303	+	}
1304	+
1305	+	/**
1306	+	* This duplicates java.util.AbstractMap.SimpleEntry until this class
1307	+	* is made accessible.
1308	+	*/
1309	+	static final class SimpleEntry<K,V> implements Entry<K,V> {
1310	+	K key;
1311	+	V value;
1312	+
1313	+	public SimpleEntry(K key, V value) {
1314	+	this.key   = key;
1315	+	this.value = value;
1316	+	}
1317	+
1318	+	public SimpleEntry(Entry<K,V> e) {
1319	+	this.key   = e.getKey();
1320	+	this.value = e.getValue();
1321	+	}
1322	+
1323	+	public K getKey() {
1324	+	return key;
1325	+	}
1326	+
1327	+	public V getValue() {
1328	+	return value;
1329	+	}
1330	+
1331	+	public V setValue(V value) {
1332	+	V oldValue = this.value;
1333	+	this.value = value;
1334	+	return oldValue;
1335	+	}
1336	+
1337	+	public boolean equals(Object o) {
1338	+	if (!(o instanceof Map.Entry))
1339	+	return false;
1340	+	Map.Entry e = (Map.Entry)o;
1341	+	return eq(key, e.getKey()) && eq(value, e.getValue());
1342	+	}
1343	+
1344	+	public int hashCode() {
1345	+	return ((key   == null)   ? 0 :   key.hashCode()) ^
1346	+	((value == null)   ? 0 : value.hashCode());
1347	+	}
1348	+
1349	+	public String toString() {
1350	+	return key + "=" + value;
1351	+	}
1352	+
1353	+	static boolean eq(Object o1, Object o2) {
1354	+	return (o1 == null ? o2 == null : o1.equals(o2));
1355	+	}
1356		}
1357
1358		/* ---------------- Serialization Support -------------- */

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