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Comparing jsr166/src/jsr166x/ConcurrentSkipListMap.java (file contents):
Revision 1.3 by dl, Tue Sep 7 11:37:57 2004 UTC vs.
Revision 1.11 by jsr166, Sat Nov 13 05:59:24 2010 UTC

#	Line 4 | Line 4
4		* http://creativecommons.org/licenses/publicdomain
5		*/
6
7	<	package jsr166x;
7	>	package jsr166x;
8
9		import java.util.*;
10		import java.util.concurrent.*;
#	Line 27 | Line 27 | import java.util.concurrent.atomic.*;
27		* elements reflecting the state of the map at some point at or since
28		* the creation of the iterator.  They do <em>not</em> throw {@link
29		* ConcurrentModificationException}, and may proceed concurrently with
30	<	* other operations.
30	>	* other operations. Ascending key ordered views and their iterators
31	>	* are faster than descending ones.
32		*
33	<	* <p> All <tt>Map.Entry</tt> pairs returned by methods in this class
33	>	* <p>All <tt>Map.Entry</tt> pairs returned by methods in this class
34		* and its views represent snapshots of mappings at the time they were
35		* produced. They do <em>not</em> support the <tt>Entry.setValue</tt>
36		* method. (Note however that it is possible to change mappings in the
#	Line 39 | Line 40 | import java.util.concurrent.atomic.*;
40		* <p>Beware that, unlike in most collections, the <tt>size</tt>
41		* method is <em>not</em> a constant-time operation. Because of the
42		* asynchronous nature of these maps, determining the current number
43	<	* of elements requires a traversal of the elements.
43	>	* of elements requires a traversal of the elements.  Additionally,
44	>	* the bulk operations <tt>putAll</tt>, <tt>equals</tt>, and
45	>	* <tt>clear</tt> are <em>not</em> guaranteed to be performed
46	>	* atomically. For example, an iterator operating concurrently with a
47	>	* <tt>putAll</tt> operation might view only some of the added
48	>	* elements.
49		*
50		* <p>This class and its views and iterators implement all of the
51		* <em>optional</em> methods of the {@link Map} and {@link Iterator}
#	Line 50 | Line 56 | import java.util.concurrent.atomic.*;
56		*
57		* @author Doug Lea
58		* @param <K> the type of keys maintained by this map
59	<	* @param <V> the type of mapped values
59	>	* @param <V> the type of mapped values
60		*/
61	<	public class ConcurrentSkipListMap<K,V> extends AbstractMap<K,V>
61	>	public class ConcurrentSkipListMap<K,V> extends AbstractMap<K,V>
62		implements ConcurrentNavigableMap<K,V>,
63	<	Cloneable,
63	>	Cloneable,
64		java.io.Serializable {
65		/*
66		* This class implements a tree-like two-dimensionally linked skip
#	Line 68 | Line 74 | public class ConcurrentSkipListMap<K,V>
74		* possible list with 2 levels of index:
75		*
76		* Head nodes          Index nodes
77	<	* +-+     right       +-+                      +-+
77	>	* +-+    right        +-+                      +-+
78		* |2|---------------->| |--------------------->| |->null
79	<	* +-+                 +-+                      +-+
79	>	* +-+                 +-+                      +-+
80		*  | down              |                        |
81		*  v                   v                        v
82	<	* +-+            +-+  +-+       +-+            +-+       +-+
82	>	* +-+            +-+  +-+       +-+            +-+       +-+
83		* |1|----------->| |->| |------>| |----------->| |------>| |->null
84	<	* +-+            +-+  +-+       +-+            +-+       +-+
85	<	*  |              |    |         |              |         |
86	<	*  v   Nodes      v    v         v              v         v
87	<	* +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+
84	>	* +-+            +-+  +-+       +-+            +-+       +-+
85	>	*  v              |    |         |              |         |
86	>	* Nodes  next     v    v         v              v         v
87	>	* +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+
88		* | |->|A|->|B|->|C|->|D|->|E|->|F|->|G|->|H|->|I|->|J|->|K|->null
89	<	* +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+
89	>	* +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+  +-+
90		*
91		* The base lists use a variant of the HM linked ordered set
92	<	* algorithm (See Tim Harris, "A pragmatic implementation of
92	>	* algorithm. See Tim Harris, "A pragmatic implementation of
93		* non-blocking linked lists"
94		* http://www.cl.cam.ac.uk/~tlh20/publications.html and Maged
95		* Michael "High Performance Dynamic Lock-Free Hash Tables and
96		* List-Based Sets"
97	<	* http://www.research.ibm.com/people/m/michael/pubs.htm).  The
98	<	* basic idea in these lists is to mark pointers of deleted nodes
99	<	* when deleting, and when traversing to keep track of triples
97	>	* http://www.research.ibm.com/people/m/michael/pubs.htm.  The
98	>	* basic idea in these lists is to mark the "next" pointers of
99	>	* deleted nodes when deleting to avoid conflicts with concurrent
100	>	* insertions, and when traversing to keep track of triples
101		* (predecessor, node, successor) in order to detect when and how
102		* to unlink these deleted nodes.
103		*
#	Line 138 | Line 145 | public class ConcurrentSkipListMap<K,V>
145		* Here's the sequence of events for a deletion of node n with
146		* predecessor b and successor f, initially:
147		*
148	<	*        +------+       +------+      +------+
148	>	*        +------+       +------+      +------+
149		*   ...  |   b  |------>|   n  |----->|   f  | ...
150	<	*        +------+       +------+      +------+
150	>	*        +------+       +------+      +------+
151		*
152		* 1. CAS n's value field from non-null to null.
153		*    From this point on, no public operations encountering
#	Line 154 | Line 161 | public class ConcurrentSkipListMap<K,V>
161		*
162		*        +------+       +------+      +------+       +------+
163		*   ...  |   b  |------>|   n  |----->|marker|------>|   f  | ...
164	<	*        +------+       +------+      +------+       +------+
164	>	*        +------+       +------+      +------+       +------+
165		*
166		* 3. CAS b's next pointer over both n and its marker.
167		*    From this point on, no new traversals will encounter n,
168		*    and it can eventually be GCed.
169		*        +------+                                    +------+
170		*   ...  |   b  |----------------------------------->|   f  | ...
171	<	*        +------+                                    +------+
172	<	*
171	>	*        +------+                                    +------+
172	>	*
173		* A failure at step 1 leads to simple retry due to a lost race
174		* with another operation. Steps 2-3 can fail because some other
175		* thread noticed during a traversal a node with null value and
#	Line 181 | Line 188 | public class ConcurrentSkipListMap<K,V>
188		* nodes. This doesn't change the basic algorithm except for the
189		* need to make sure base traversals start at predecessors (here,
190		* b) that are not (structurally) deleted, otherwise retrying
191	<	* after processing the deletion.
191	>	* after processing the deletion.
192		*
193		* Index levels are maintained as lists with volatile next fields,
194		* using CAS to link and unlink.  Races are allowed in index-list
#	Line 259 | Line 266 | public class ConcurrentSkipListMap<K,V>
266		* For explanation of algorithms sharing at least a couple of
267		* features with this one, see Mikhail Fomitchev's thesis
268		* (http://www.cs.yorku.ca/~mikhail/), Keir Fraser's thesis
269	<	* (http://www.cl.cam.ac.uk/users/kaf24/), and papers by
270	<	* Håkan Sundell (http://www.cs.chalmers.se/~phs/).
269	>	* (http://www.cl.cam.ac.uk/users/kaf24/), and Hakan Sundell's
270	>	* thesis (http://www.cs.chalmers.se/~phs/).
271		*
272		* Given the use of tree-like index nodes, you might wonder why
273		* this doesn't use some kind of search tree instead, which would
#	Line 285 | Line 292 | public class ConcurrentSkipListMap<K,V>
292
293		/**
294		* Special value used to identify base-level header
295	<	*/
295	>	*/
296		private static final Object BASE_HEADER = new Object();
297
298		/**
299	<	* The topmost head index of the skiplist.
299	>	* The topmost head index of the skiplist.
300		*/
301		private transient volatile HeadIndex<K,V> head;
302
#	Line 312 | Line 319 | public class ConcurrentSkipListMap<K,V>
319		private transient EntrySet entrySet;
320		/** Lazily initialized values collection */
321		private transient Values values;
322	+	/** Lazily initialized descending key set */
323	+	private transient DescendingKeySet descendingKeySet;
324	+	/** Lazily initialized descending entry set */
325	+	private transient DescendingEntrySet descendingEntrySet;
326
327		/**
328		* Initialize or reset state. Needed by constructors, clone,
#	Line 320 | Line 331 | public class ConcurrentSkipListMap<K,V>
331		*/
332		final void initialize() {
333		keySet = null;
334	<	entrySet = null;
334	>	entrySet = null;
335		values = null;
336	+	descendingEntrySet = null;
337	+	descendingKeySet = null;
338		randomSeed = (int) System.nanoTime();
339		head = new HeadIndex<K,V>(new Node<K,V>(null, BASE_HEADER, null),
340		null, null, 1);
341		}
342
343		/** Updater for casHead */
344	<	private static final
345	<	AtomicReferenceFieldUpdater<ConcurrentSkipListMap, HeadIndex>
344	>	private static final
345	>	AtomicReferenceFieldUpdater<ConcurrentSkipListMap, HeadIndex>
346		headUpdater = AtomicReferenceFieldUpdater.newUpdater
347		(ConcurrentSkipListMap.class, HeadIndex.class, "head");
348
#	Line 377 | Line 390 | public class ConcurrentSkipListMap<K,V>
390		}
391
392		/** Updater for casNext */
393	<	static final AtomicReferenceFieldUpdater<Node, Node>
393	>	static final AtomicReferenceFieldUpdater<Node, Node>
394		nextUpdater = AtomicReferenceFieldUpdater.newUpdater
395		(Node.class, Node.class, "next");
396
397		/** Updater for casValue */
398	<	static final AtomicReferenceFieldUpdater<Node, Object>
398	>	static final AtomicReferenceFieldUpdater<Node, Object>
399		valueUpdater = AtomicReferenceFieldUpdater.newUpdater
400		(Node.class, Object.class, "value");
401
389	–
402		/**
403		* compareAndSet value field
404		*/
#	Line 454 | Line 466 | public class ConcurrentSkipListMap<K,V>
466
467		/**
468		* Return value if this node contains a valid key-value pair,
469	<	* else null.
469	>	* else null.
470		* @return this node's value if it isn't a marker or header or
471		* is deleted, else null.
472		*/
#	Line 495 | Line 507 | public class ConcurrentSkipListMap<K,V>
507		volatile Index<K,V> right;
508
509		/**
510	<	* Creates index node with unknown right pointer
511	<	*/
500	<	Index(Node<K,V> node, Index<K,V> down) {
501	<	this.node = node;
502	<	this.key = node.key;
503	<	this.down = down;
504	<	}
505	<
506	<	/**
507	<	* Creates index node with known right pointer
508	<	*/
510	>	* Creates index node with given values
511	>	*/
512		Index(Node<K,V> node, Index<K,V> down, Index<K,V> right) {
513		this.node = node;
514		this.key = node.key;
#	Line 514 | Line 517 | public class ConcurrentSkipListMap<K,V>
517		}
518
519		/** Updater for casRight */
520	<	static final AtomicReferenceFieldUpdater<Index, Index>
520	>	static final AtomicReferenceFieldUpdater<Index, Index>
521		rightUpdater = AtomicReferenceFieldUpdater.newUpdater
522		(Index.class, Index.class, "right");
523
#	Line 543 | Line 546 | public class ConcurrentSkipListMap<K,V>
546		*/
547		final boolean link(Index<K,V> succ, Index<K,V> newSucc) {
548		Node<K,V> n = node;
549	<	newSucc.right = succ;
549	>	newSucc.right = succ;
550		return n.value != null && casRight(succ, newSucc);
551		}
552
#	Line 566 | Line 569 | public class ConcurrentSkipListMap<K,V>
569		*/
570		static final class HeadIndex<K,V> extends Index<K,V> {
571		final int level;
572	<	HeadIndex(Node<K,V> node, Index<K,V> down, Index<K,V> right,
570	<	int level) {
572	>	HeadIndex(Node<K,V> node, Index<K,V> down, Index<K,V> right, int level) {
573		super(node, down, right);
574		this.level = level;
575		}
576	<	}
576	>	}
577
578		/* ---------------- Map.Entry support -------------- */
579
#	Line 579 | Line 581 | public class ConcurrentSkipListMap<K,V>
581		* An immutable representation of a key-value mapping as it
582		* existed at some point in time. This class does <em>not</em>
583		* support the <tt>Map.Entry.setValue</tt> method.
584	<	*/
584	>	*/
585		static class SnapshotEntry<K,V> implements Map.Entry<K,V> {
586	<	private final K key;
587	<	private final V value;
586	>	private final K key;
587	>	private final V value;
588
589		/**
590		* Creates a new entry representing the given key and value.
#	Line 590 | Line 592 | public class ConcurrentSkipListMap<K,V>
592		* @param value the value
593		*/
594		SnapshotEntry(K key, V value) {
595	<	this.key = key;
596	<	this.value = value;
597	<	}
598	<
599	<	/**
600	<	* Returns the key corresponding to this entry.
601	<	*
602	<	* @return the key corresponding to this entry.
603	<	*/
595	>	this.key = key;
596	>	this.value = value;
597	>	}
598	>
599	>	/**
600	>	* Returns the key corresponding to this entry.
601	>	*
602	>	* @return the key corresponding to this entry.
603	>	*/
604		public K getKey() {
605		return key;
606		}
607
608	<	/**
609	<	* Returns the value corresponding to this entry.
610	<	*
611	<	* @return the value corresponding to this entry.
612	<	*/
608	>	/**
609	>	* Returns the value corresponding to this entry.
610	>	*
611	>	* @return the value corresponding to this entry.
612	>	*/
613		public V getValue() {
614	<	return value;
614	>	return value;
615		}
616
617	<	/**
618	<	* Always fails, throwing <tt>UnsupportedOperationException</tt>.
619	<	* @throws UnsupportedOperationException always.
617	>	/**
618	>	* Always fails, throwing <tt>UnsupportedOperationException</tt>.
619	>	* @throws UnsupportedOperationException always.
620		*/
621		public V setValue(V value) {
622		throw new UnsupportedOperationException();
#	Line 647 | Line 649 | public class ConcurrentSkipListMap<K,V>
649		* @return a String representation of this entry.
650		*/
651		public String toString() {
652	<	return getKey() + "=" + getValue();
652	>	return getKey() + "=" + getValue();
653		}
654		}
655
#	Line 686 | Line 688 | public class ConcurrentSkipListMap<K,V>
688		* which is propagated back to caller.
689		*/
690		private Comparable<K> comparable(Object key) throws ClassCastException {
691	<	if (key == null)
691	>	if (key == null)
692		throw new NullPointerException();
693	<	return (comparator != null)
694	<	? new ComparableUsingComparator(key, comparator)
693	>	return (comparator != null)
694	>	? new ComparableUsingComparator(key, comparator)
695		: (Comparable<K>)key;
696		}
697
#	Line 707 | Line 709 | public class ConcurrentSkipListMap<K,V>
709
710		/**
711		* Return true if given key greater than or equal to least and
712	<	* strictly less than fence. Needed mainly in submap operations.
712	>	* strictly less than fence, bypassing either test if least or
713	>	* fence oare null. Needed mainly in submap operations.
714		*/
715		boolean inHalfOpenRange(K key, K least, K fence) {
716	<	if (key == null)
716	>	if (key == null)
717		throw new NullPointerException();
718		return ((least == null || compare(key, least) >= 0) &&
719		(fence == null || compare(key, fence) <  0));
#	Line 721 | Line 724 | public class ConcurrentSkipListMap<K,V>
724		* or equal to fence. Needed mainly in submap operations.
725		*/
726		boolean inOpenRange(K key, K least, K fence) {
727	<	if (key == null)
727	>	if (key == null)
728		throw new NullPointerException();
729		return ((least == null || compare(key, least) >= 0) &&
730		(fence == null || compare(key, fence) <= 0));
#	Line 735 | Line 738 | public class ConcurrentSkipListMap<K,V>
738		* unlinks indexes to deleted nodes found along the way.  Callers
739		* rely on this side-effect of clearing indices to deleted nodes.
740		* @param key the key
741	<	* @return a predecessor of key
741	>	* @return a predecessor of key
742		*/
743		private Node<K,V> findPredecessor(Comparable<K> key) {
744		for (;;) {
#	Line 754 | Line 757 | public class ConcurrentSkipListMap<K,V>
757		continue;
758		}
759		}
760	<	if ((d = q.down) != null)
760	>	if ((d = q.down) != null)
761		q = d;
762		else
763		return q.node;
#	Line 784 | Line 787 | public class ConcurrentSkipListMap<K,V>
787		*       here because doing so would not usually outweigh cost of
788		*       restarting.
789		*
790	<	*   (3) n is a marker or n's predecessor's value field is null,
790	>	*   (3) n is a marker or n's predecessor's value field is null,
791		*       indicating (among other possibilities) that
792		*       findPredecessor returned a deleted node. We can't unlink
793		*       the node because we don't know its predecessor, so rely
#	Line 797 | Line 800 | public class ConcurrentSkipListMap<K,V>
800		*       links, and so will retry anyway.
801		*
802		* The traversal loops in doPut, doRemove, and findNear all
803	<	* include with the same three kinds of checks. And specialized
804	<	* versions appear in doRemoveFirstEntry, findFirst, and
803	>	* include the same three kinds of checks. And specialized
804	>	* versions appear in doRemoveFirst, doRemoveLast, findFirst, and
805		* findLast. They can't easily share code because each uses the
806		* reads of fields held in locals occurring in the orders they
807		* were performed.
808	<	*
808	>	*
809		* @param key the key
810		* @return node holding key, or null if no such.
811		*/
#	Line 811 | Line 814 | public class ConcurrentSkipListMap<K,V>
814		Node<K,V> b = findPredecessor(key);
815		Node<K,V> n = b.next;
816		for (;;) {
817	<	if (n == null)
817	>	if (n == null)
818		return null;
819		Node<K,V> f = n.next;
820		if (n != b.next)                // inconsistent read
#	Line 826 | Line 829 | public class ConcurrentSkipListMap<K,V>
829		int c = key.compareTo(n.key);
830		if (c < 0)
831		return null;
832	<	if (c == 0)
832	>	if (c == 0)
833		return n;
834		b = n;
835		n = f;
#	Line 834 | Line 837 | public class ConcurrentSkipListMap<K,V>
837		}
838		}
839
840	<	/**
841	<	* Specialized variant of findNode to perform map.get. Does a weak
840	>	/**
841	>	* Specialized variant of findNode to perform Map.get. Does a weak
842		* traversal, not bothering to fix any deleted index nodes,
843		* returning early if it happens to see key in index, and passing
844		* over any deleted base nodes, falling back to getUsingFindNode
#	Line 853 | Line 856 | public class ConcurrentSkipListMap<K,V>
856		for (;;) {
857		K rk;
858		Index<K,V> d, r;
859	<	if ((r = q.right) != null &&
859	>	if ((r = q.right) != null &&
860		(rk = r.key) != null && rk != bound) {
861		int c = key.compareTo(rk);
862		if (c > 0) {
#	Line 866 | Line 869 | public class ConcurrentSkipListMap<K,V>
869		}
870		bound = rk;
871		}
872	<	if ((d = q.down) != null)
872	>	if ((d = q.down) != null)
873		q = d;
874		else {
875		for (Node<K,V> n = q.node.next; n != null; n = n.next) {
#	Line 893 | Line 896 | public class ConcurrentSkipListMap<K,V>
896		* @return the value, or null if absent
897		*/
898		private V getUsingFindNode(Comparable<K> key) {
899	<	// Loop needed here and elsewhere to protect against value
900	<	// field going null just as it is about to be returned.
899	>	/*
900	>	* Loop needed here and elsewhere in case value field goes
901	>	* null just as it is about to be returned, in which case we
902	>	* lost a race with a deletion, so must retry.
903	>	*/
904		for (;;) {
905		Node<K,V> n = findNode(key);
906		if (n == null)
#	Line 910 | Line 916 | public class ConcurrentSkipListMap<K,V>
916		/**
917		* Main insertion method.  Adds element if not present, or
918		* replaces value if present and onlyIfAbsent is false.
919	<	* @param kkey the key
919	>	* @param kkey the key
920		* @param value  the value that must be associated with key
921		* @param onlyIfAbsent if should not insert if already present
922		* @return the old value, or null if newly inserted
#	Line 924 | Line 930 | public class ConcurrentSkipListMap<K,V>
930		if (n != null) {
931		Node<K,V> f = n.next;
932		if (n != b.next)               // inconsistent read
933	<	break;;
933	>	break;
934		Object v = n.value;
935		if (v == null) {               // n is deleted
936		n.helpDelete(b, f);
#	Line 946 | Line 952 | public class ConcurrentSkipListMap<K,V>
952		}
953		// else c < 0; fall through
954		}
955	<
955	>
956		Node<K,V> z = new Node<K,V>(kkey, value, n);
957	<	if (!b.casNext(n, z))
957	>	if (!b.casNext(n, z))
958		break;         // restart if lost race to append to b
959	<	int level = randomLevel();
960	<	if (level > 0)
959	>	int level = randomLevel();
960	>	if (level > 0)
961		insertIndex(z, level);
962		return null;
963		}
#	Line 973 | Line 979 | public class ConcurrentSkipListMap<K,V>
979		int level = 0;
980		int r = randomSeed;
981		randomSeed = r * 134775813 + 1;
982	<	if (r < 0) {
983	<	while ((r <<= 1) > 0)
982	>	if (r < 0) {
983	>	while ((r <<= 1) > 0)
984		++level;
985		}
986		return level;
#	Line 992 | Line 998 | public class ConcurrentSkipListMap<K,V>
998		if (level <= max) {
999		Index<K,V> idx = null;
1000		for (int i = 1; i <= level; ++i)
1001	<	idx = new Index<K,V>(z, idx);
1001	>	idx = new Index<K,V>(z, idx, null);
1002		addIndex(idx, h, level);
1003
1004		} else { // Add a new level
#	Line 1007 | Line 1013 | public class ConcurrentSkipListMap<K,V>
1013		level = max + 1;
1014		Index<K,V>[] idxs = (Index<K,V>[])new Index[level+1];
1015		Index<K,V> idx = null;
1016	<	for (int i = 1; i <= level; ++i)
1017	<	idxs[i] = idx = new Index<K,V>(z, idx);
1016	>	for (int i = 1; i <= level; ++i)
1017	>	idxs[i] = idx = new Index<K,V>(z, idx, null);
1018
1019		HeadIndex<K,V> oldh;
1020		int k;
#	Line 1021 | Line 1027 | public class ConcurrentSkipListMap<K,V>
1027		}
1028		HeadIndex<K,V> newh = oldh;
1029		Node<K,V> oldbase = oldh.node;
1030	<	for (int j = oldLevel+1; j <= level; ++j)
1030	>	for (int j = oldLevel+1; j <= level; ++j)
1031		newh = new HeadIndex<K,V>(oldbase, newh, idxs[j], j);
1032		if (casHead(oldh, newh)) {
1033		k = oldLevel;
#	Line 1059 | Line 1065 | public class ConcurrentSkipListMap<K,V>
1065		if (q.unlink(r))
1066		continue;
1067		else
1068	<	break;
1068	>	break;
1069		}
1070		if (c > 0) {
1071		q = r;
#	Line 1073 | Line 1079 | public class ConcurrentSkipListMap<K,V>
1079		findNode(key); // cleans up
1080		return;
1081		}
1082	<	if (!q.link(r, t))
1082	>	if (!q.link(r, t))
1083		break; // restart
1084		if (--insertionLevel == 0) {
1085		// need final deletion check before return
1086	<	if (t.indexesDeletedNode())
1087	<	findNode(key);
1086	>	if (t.indexesDeletedNode())
1087	>	findNode(key);
1088		return;
1089		}
1090		}
1091
1092	<	if (j > insertionLevel && j <= indexLevel)
1092	>	if (j > insertionLevel && j <= indexLevel)
1093		t = t.down;
1094		q = q.down;
1095		--j;
#	Line 1098 | Line 1104 | public class ConcurrentSkipListMap<K,V>
1104		* deletion marker, unlinks predecessor, removes associated index
1105		* nodes, and possibly reduces head index level.
1106		*
1107	<	* Index node are cleared out simply by calling findPredecessor.
1107	>	* Index nodes are cleared out simply by calling findPredecessor.
1108		* which unlinks indexes to deleted nodes found along path to key,
1109		* which will include the indexes to this node.  This is done
1110		* unconditionally. We can't check beforehand whether there are
1111		* index nodes because it might be the case that some or all
1112		* indexes hadn't been inserted yet for this node during initial
1113		* search for it, and we'd like to ensure lack of garbage
1114	<	* retention, so must call to be sure.
1114	>	* retention, so must call to be sure.
1115		*
1116		* @param okey the key
1117		* @param value if non-null, the value that must be
#	Line 1114 | Line 1120 | public class ConcurrentSkipListMap<K,V>
1120		*/
1121		private V doRemove(Object okey, Object value) {
1122		Comparable<K> key = comparable(okey);
1123	<	for (;;) {
1123	>	for (;;) {
1124		Node<K,V> b = findPredecessor(key);
1125		Node<K,V> n = b.next;
1126		for (;;) {
1127	<	if (n == null)
1127	>	if (n == null)
1128		return null;
1129		Node<K,V> f = n.next;
1130		if (n != b.next)                    // inconsistent read
#	Line 1138 | Line 1144 | public class ConcurrentSkipListMap<K,V>
1144		n = f;
1145		continue;
1146		}
1147	<	if (value != null && !value.equals(v))
1148	<	return null;
1149	<	if (!n.casValue(v, null))
1147	>	if (value != null && !value.equals(v))
1148	>	return null;
1149	>	if (!n.casValue(v, null))
1150		break;
1151	<	if (!n.appendMarker(f) || !b.casNext(n, f))
1151	>	if (!n.appendMarker(f) || !b.casNext(n, f))
1152		findNode(key);                  // Retry via findNode
1153		else {
1154		findPredecessor(key);           // Clean index
1155	<	if (head.right == null)
1155	>	if (head.right == null)
1156		tryReduceLevel();
1157		}
1158		return (V)v;
#	Line 1158 | Line 1164 | public class ConcurrentSkipListMap<K,V>
1164		* Possibly reduce head level if it has no nodes.  This method can
1165		* (rarely) make mistakes, in which case levels can disappear even
1166		* though they are about to contain index nodes. This impacts
1167	<	* performance, not correctness.  To minimize mistakes and also to
1168	<	* reduce hysteresis, the level is reduced by one only if the
1167	>	* performance, not correctness.  To minimize mistakes as well as
1168	>	* to reduce hysteresis, the level is reduced by one only if the
1169		* topmost three levels look empty. Also, if the removed level
1170		* looks non-empty after CAS, we try to change it back quick
1171		* before anyone notices our mistake! (This trick works pretty
#	Line 1179 | Line 1185 | public class ConcurrentSkipListMap<K,V>
1185		HeadIndex<K,V> d;
1186		HeadIndex<K,V> e;
1187		if (h.level > 3 &&
1188	<	(d = (HeadIndex<K,V>)h.down) != null &&
1189	<	(e = (HeadIndex<K,V>)d.down) != null &&
1190	<	e.right == null &&
1191	<	d.right == null &&
1188	>	(d = (HeadIndex<K,V>)h.down) != null &&
1189	>	(e = (HeadIndex<K,V>)d.down) != null &&
1190	>	e.right == null &&
1191	>	d.right == null &&
1192		h.right == null &&
1193		casHead(h, d) && // try to set
1194		h.right != null) // recheck
1195		casHead(d, h);   // try to backout
1196		}
1197
1198	+	/**
1199	+	* Version of remove with boolean return. Needed by view classes
1200	+	*/
1201	+	boolean removep(Object key) {
1202	+	return doRemove(key, null) != null;
1203	+	}
1204
1205	<	/* ---------------- Positional operations -------------- */
1205	>	/* ---------------- Finding and removing first element -------------- */
1206
1207		/**
1208	<	* Specialized version of find to get first valid node
1208	>	* Specialized variant of findNode to get first valid node
1209		* @return first node or null if empty
1210		*/
1211		Node<K,V> findFirst() {
1212		for (;;) {
1201	–	// cheaper checks because we know head is never deleted
1213		Node<K,V> b = head.node;
1214		Node<K,V> n = b.next;
1215		if (n == null)
1216		return null;
1217	<	if (n.value != null)
1217	>	if (n.value != null)
1218		return n;
1219		n.helpDelete(b, n.next);
1220		}
1221		}
1222
1223		/**
1224	<	* Remove first entry; return its key or null if empty.
1225	<	* Used by ConcurrentSkipListSet
1224	>	* Remove first entry; return either its key or a snapshot.
1225	>	* @param keyOnly if true return key, else return SnapshotEntry
1226	>	* (This is a little ugly, but avoids code duplication.)
1227	>	* @return null if empty, first key if keyOnly true, else key,value entry
1228		*/
1229	<	K removeFirstKey() {
1230	<	for (;;) {
1218	<	Node<K,V> b = head.node;
1219	<	Node<K,V> n = b.next;
1220	<	if (n == null)
1221	<	return null;
1222	<	Node<K,V> f = n.next;
1223	<	if (n != b.next)
1224	<	continue;
1225	<	Object v = n.value;
1226	<	if (v == null) {
1227	<	n.helpDelete(b, f);
1228	<	continue;
1229	<	}
1230	<	if (!n.casValue(v, null))
1231	<	continue;
1232	<	if (!n.appendMarker(f) || !b.casNext(n, f))
1233	<	findFirst(); // retry
1234	<	clearIndexToFirst();
1235	<	return n.key;
1236	<	}
1237	<	}
1238	<
1239	<	/**
1240	<	* Remove first entry; return SnapshotEntry or null if empty.
1241	<	*/
1242	<	private SnapshotEntry<K,V> doRemoveFirstEntry() {
1243	<	/*
1244	<	* This must be mostly duplicated from removeFirstKey because we
1245	<	* need to save the last value read before it is nulled out
1246	<	*/
1247	<	for (;;) {
1229	>	Object doRemoveFirst(boolean keyOnly) {
1230	>	for (;;) {
1231		Node<K,V> b = head.node;
1232		Node<K,V> n = b.next;
1233	<	if (n == null)
1233	>	if (n == null)
1234		return null;
1235		Node<K,V> f = n.next;
1236		if (n != b.next)
#	Line 1262 | Line 1245 | public class ConcurrentSkipListMap<K,V>
1245		if (!n.appendMarker(f) || !b.casNext(n, f))
1246		findFirst(); // retry
1247		clearIndexToFirst();
1248	<	return new SnapshotEntry<K,V>(n.key, (V)v);
1248	>	K key = n.key;
1249	>	return (keyOnly)? key : new SnapshotEntry<K,V>(key, (V)v);
1250		}
1251		}
1252
1253		/**
1254		* Clear out index nodes associated with deleted first entry.
1255	<	* Needed by removeFirstKey and removeFirstEntry
1255	>	* Needed by doRemoveFirst
1256		*/
1257		private void clearIndexToFirst() {
1258		for (;;) {
#	Line 1276 | Line 1260 | public class ConcurrentSkipListMap<K,V>
1260		for (;;) {
1261		Index<K,V> r = q.right;
1262		if (r != null && r.indexesDeletedNode() && !q.unlink(r))
1263	<	break;
1263	>	break;
1264		if ((q = q.down) == null) {
1265	<	if (head.right == null)
1265	>	if (head.right == null)
1266		tryReduceLevel();
1267		return;
1268		}
#	Line 1286 | Line 1270 | public class ConcurrentSkipListMap<K,V>
1270		}
1271		}
1272
1273	+	/**
1274	+	* Remove first entry; return key or null if empty.
1275	+	*/
1276	+	K pollFirstKey() {
1277	+	return (K)doRemoveFirst(true);
1278	+	}
1279	+
1280	+	/* ---------------- Finding and removing last element -------------- */
1281	+
1282		/**
1283		* Specialized version of find to get last valid node
1284		* @return last node or null if empty
#	Line 1303 | Line 1296 | public class ConcurrentSkipListMap<K,V>
1296		if (r.indexesDeletedNode()) {
1297		q.unlink(r);
1298		q = head; // restart
1299	<	}
1299	>	}
1300		else
1301		q = r;
1302		} else if ((d = q.down) != null) {
#	Line 1312 | Line 1305 | public class ConcurrentSkipListMap<K,V>
1305		Node<K,V> b = q.node;
1306		Node<K,V> n = b.next;
1307		for (;;) {
1308	<	if (n == null)
1308	>	if (n == null)
1309		return (b.isBaseHeader())? null : b;
1310		Node<K,V> f = n.next;            // inconsistent read
1311		if (n != b.next)
#	Line 1332 | Line 1325 | public class ConcurrentSkipListMap<K,V>
1325		}
1326		}
1327
1328	+
1329		/**
1330	<	* Temporary helper method for two-pass implementation of
1331	<	* removeLastEntry, mostly pasted from doRemove.
1332	<	* TODO: replace with one-pass implementation
1330	>	* Specialized version of doRemove for last entry.
1331	>	* @param keyOnly if true return key, else return SnapshotEntry
1332	>	* @return null if empty, last key if keyOnly true, else key,value entry
1333		*/
1334	<	private Object removeIfLast(K kkey) {
1335	<	Comparable<K> key = comparable(kkey);
1336	<	for (;;) {
1343	<	Node<K,V> b = findPredecessor(key);
1334	>	Object doRemoveLast(boolean keyOnly) {
1335	>	for (;;) {
1336	>	Node<K,V> b = findPredecessorOfLast();
1337		Node<K,V> n = b.next;
1338	<	for (;;) {
1339	<	if (n == null)
1338	>	if (n == null) {
1339	>	if (b.isBaseHeader())               // empty
1340		return null;
1341	+	else
1342	+	continue; // all b's successors are deleted; retry
1343	+	}
1344	+	for (;;) {
1345		Node<K,V> f = n.next;
1346		if (n != b.next)                    // inconsistent read
1347		break;
#	Line 1355 | Line 1352 | public class ConcurrentSkipListMap<K,V>
1352		}
1353		if (v == n || b.value == null)      // b is deleted
1354		break;
1355	<	int c = key.compareTo(n.key);
1359	<	if (c < 0)
1360	<	return null;
1361	<	if (c > 0) {
1355	>	if (f != null) {
1356		b = n;
1357		n = f;
1358		continue;
1359		}
1360	<	if (f != null)                       // fail if n not last
1361	<	return null;
1362	<	if (!n.casValue(v, null))
1363	<	return null;
1364	<	if (!n.appendMarker(f) || !b.casNext(n, f))
1365	<	findNode(key);                  // Retry via findNode
1360	>	if (!n.casValue(v, null))
1361	>	break;
1362	>	K key = n.key;
1363	>	Comparable<K> ck = comparable(key);
1364	>	if (!n.appendMarker(f) || !b.casNext(n, f))
1365	>	findNode(ck);                  // Retry via findNode
1366		else {
1367	<	findPredecessor(key);           // Clean index
1368	<	if (head.right == null)
1367	>	findPredecessor(ck);           // Clean index
1368	>	if (head.right == null)
1369		tryReduceLevel();
1370		}
1371	<	return v;
1371	>	return (keyOnly)? key : new SnapshotEntry<K,V>(key, (V)v);
1372		}
1373		}
1374		}
1375
1376		/**
1377	<	* Remove last entry; return SnapshotEntry or null if empty.
1377	>	* Specialized variant of findPredecessor to get predecessor of
1378	>	* last valid node. Needed by doRemoveLast. It is possible that
1379	>	* all successors of returned node will have been deleted upon
1380	>	* return, in which case this method can be retried.
1381	>	* @return likely predecessor of last node.
1382		*/
1383	<	private SnapshotEntry<K,V> doRemoveLastEntry() {
1383	>	private Node<K,V> findPredecessorOfLast() {
1384		for (;;) {
1385	<	Node<K,V> l = findLast();
1386	<	if (l == null)
1387	<	return null;
1388	<	K k = l.key;
1389	<	Object v = removeIfLast(k);
1390	<	if (v != null)
1391	<	return new SnapshotEntry<K, V>(k, (V)v);
1385	>	Index<K,V> q = head;
1386	>	for (;;) {
1387	>	Index<K,V> d, r;
1388	>	if ((r = q.right) != null) {
1389	>	if (r.indexesDeletedNode()) {
1390	>	q.unlink(r);
1391	>	break;    // must restart
1392	>	}
1393	>	// proceed as far across as possible without overshooting
1394	>	if (r.node.next != null) {
1395	>	q = r;
1396	>	continue;
1397	>	}
1398	>	}
1399	>	if ((d = q.down) != null)
1400	>	q = d;
1401	>	else
1402	>	return q.node;
1403	>	}
1404		}
1405		}
1406	<
1406	>
1407		/**
1408	<	* Remove last entry; return key or null if empty.
1408	>	* Remove last entry; return key or null if empty.
1409		*/
1410	<	K removeLastKey() {
1411	<	for (;;) {
1402	<	Node<K,V> l = findLast();
1403	<	if (l == null)
1404	<	return null;
1405	<	K k = l.key;
1406	<	if (removeIfLast(k) != null)
1407	<	return k;
1408	<	}
1410	>	K pollLastKey() {
1411	>	return (K)doRemoveLast(true);
1412		}
1413
1414		/* ---------------- Relational operations -------------- */
#	Line 1414 | Line 1417 | public class ConcurrentSkipListMap<K,V>
1417
1418		private static final int EQ = 1;
1419		private static final int LT = 2;
1420	<	private static final int GT = 0;
1420	>	private static final int GT = 0; // Actually checked as !LT
1421
1422		/**
1423		* Utility for ceiling, floor, lower, higher methods.
#	Line 1428 | Line 1431 | public class ConcurrentSkipListMap<K,V>
1431		Node<K,V> b = findPredecessor(key);
1432		Node<K,V> n = b.next;
1433		for (;;) {
1434	<	if (n == null)
1434	>	if (n == null)
1435		return ((rel & LT) == 0 || b.isBaseHeader())? null : b;
1436		Node<K,V> f = n.next;
1437		if (n != b.next)                  // inconsistent read
#	Line 1469 | Line 1472 | public class ConcurrentSkipListMap<K,V>
1472		}
1473		}
1474
1475	+	/**
1476	+	* Return ceiling, or first node if key is <tt>null</tt>
1477	+	*/
1478	+	Node<K,V> findCeiling(K key) {
1479	+	return (key == null)? findFirst() : findNear(key, GT|EQ);
1480	+	}
1481	+
1482	+	/**
1483	+	* Return lower node, or last node if key is <tt>null</tt>
1484	+	*/
1485	+	Node<K,V> findLower(K key) {
1486	+	return (key == null)? findLast() : findNear(key, LT);
1487	+	}
1488	+
1489	+	/**
1490	+	* Return SnapshotEntry or key for results of findNear ofter screening
1491	+	* to ensure result is in given range. Needed by submaps.
1492	+	* @param kkey the key
1493	+	* @param rel the relation -- OR'ed combination of EQ, LT, GT
1494	+	* @param least minimum allowed key value
1495	+	* @param fence key greater than maximum allowed key value
1496	+	* @param keyOnly if true return key, else return SnapshotEntry
1497	+	* @return Key or Entry fitting relation, or <tt>null</tt> if no such
1498	+	*/
1499	+	Object getNear(K kkey, int rel, K least, K fence, boolean keyOnly) {
1500	+	K key = kkey;
1501	+	// Don't return keys less than least
1502	+	if ((rel & LT) == 0) {
1503	+	if (compare(key, least) < 0) {
1504	+	key = least;
1505	+	rel = rel | EQ;
1506	+	}
1507	+	}
1508	+
1509	+	for (;;) {
1510	+	Node<K,V> n = findNear(key, rel);
1511	+	if (n == null || !inHalfOpenRange(n.key, least, fence))
1512	+	return null;
1513	+	K k = n.key;
1514	+	V v = n.getValidValue();
1515	+	if (v != null)
1516	+	return keyOnly? k : new SnapshotEntry<K,V>(k, v);
1517	+	}
1518	+	}
1519	+
1520	+	/**
1521	+	* Find and remove least element of subrange.
1522	+	* @param least minimum allowed key value
1523	+	* @param fence key greater than maximum allowed key value
1524	+	* @param keyOnly if true return key, else return SnapshotEntry
1525	+	* @return least Key or Entry, or <tt>null</tt> if no such
1526	+	*/
1527	+	Object removeFirstEntryOfSubrange(K least, K fence, boolean keyOnly) {
1528	+	for (;;) {
1529	+	Node<K,V> n = findCeiling(least);
1530	+	if (n == null)
1531	+	return null;
1532	+	K k = n.key;
1533	+	if (fence != null && compare(k, fence) >= 0)
1534	+	return null;
1535	+	V v = doRemove(k, null);
1536	+	if (v != null)
1537	+	return (keyOnly)? k : new SnapshotEntry<K,V>(k, v);
1538	+	}
1539	+	}
1540	+
1541	+	/**
1542	+	* Find and remove greatest element of subrange.
1543	+	* @param least minimum allowed key value
1544	+	* @param fence key greater than maximum allowed key value
1545	+	* @param keyOnly if true return key, else return SnapshotEntry
1546	+	* @return least Key or Entry, or <tt>null</tt> if no such
1547	+	*/
1548	+	Object removeLastEntryOfSubrange(K least, K fence, boolean keyOnly) {
1549	+	for (;;) {
1550	+	Node<K,V> n = findLower(fence);
1551	+	if (n == null)
1552	+	return null;
1553	+	K k = n.key;
1554	+	if (least != null && compare(k, least) < 0)
1555	+	return null;
1556	+	V v = doRemove(k, null);
1557	+	if (v != null)
1558	+	return (keyOnly)? k : new SnapshotEntry<K,V>(k, v);
1559	+	}
1560	+	}
1561	+
1562		/* ---------------- Constructors -------------- */
1563
1564		/**
1565		* Constructs a new empty map, sorted according to the keys' natural
1566	<	* order.
1566	>	* order.
1567		*/
1568		public ConcurrentSkipListMap() {
1569		this.comparator = null;
#	Line 1494 | Line 1584 | public class ConcurrentSkipListMap<K,V>
1584
1585		/**
1586		* Constructs a new map containing the same mappings as the given map,
1587	<	* sorted according to the keys' <i>natural order</i>.
1587	>	* sorted according to the keys' <i>natural order</i>.
1588		*
1589		* @param  m the map whose mappings are to be placed in this map.
1590		* @throws ClassCastException if the keys in m are not Comparable, or
#	Line 1509 | Line 1599 | public class ConcurrentSkipListMap<K,V>
1599
1600		/**
1601		* Constructs a new map containing the same mappings as the given
1602	<	* <tt>SortedMap</tt>, sorted according to the same ordering.
1603	<	* @param  m the sorted map whose mappings are to be placed in this map,
1604	<	*         and whose comparator is to be used to sort this map.
1605	<	* @throws NullPointerException if the specified sorted map is <tt>null</tt>.
1602	>	* <tt>SortedMap</tt>, sorted according to the same ordering.
1603	>	* @param m the sorted map whose mappings are to be placed in this
1604	>	* map, and whose comparator is to be used to sort this map.
1605	>	* @throws NullPointerException if the specified sorted map is
1606	>	* <tt>null</tt>.
1607		*/
1608		public ConcurrentSkipListMap(SortedMap<K, ? extends V> m) {
1609		this.comparator = m.comparator();
#	Line 1556 | Line 1647 | public class ConcurrentSkipListMap<K,V>
1647		ArrayList<Index<K,V>> preds = new ArrayList<Index<K,V>>();
1648
1649		// initialize
1650	<	for (int i = 0; i <= h.level; ++i)
1650	>	for (int i = 0; i <= h.level; ++i)
1651		preds.add(null);
1652		Index<K,V> q = h;
1653		for (int i = h.level; i > 0; --i) {
#	Line 1564 | Line 1655 | public class ConcurrentSkipListMap<K,V>
1655		q = q.down;
1656		}
1657
1658	<	Iterator<? extends Map.Entry<? extends K, ? extends V>> it =
1658	>	Iterator<? extends Map.Entry<? extends K, ? extends V>> it =
1659		map.entrySet().iterator();
1660		while (it.hasNext()) {
1661		Map.Entry<? extends K, ? extends V> e = it.next();
#	Line 1580 | Line 1671 | public class ConcurrentSkipListMap<K,V>
1671		if (j > 0) {
1672		Index<K,V> idx = null;
1673		for (int i = 1; i <= j; ++i) {
1674	<	idx = new Index<K,V>(z, idx);
1675	<	if (i > h.level)
1674	>	idx = new Index<K,V>(z, idx, null);
1675	>	if (i > h.level)
1676		h = new HeadIndex<K,V>(h.node, h, idx, i);
1677
1678		if (i < preds.size()) {
#	Line 1601 | Line 1692 | public class ConcurrentSkipListMap<K,V>
1692		* Save the state of the <tt>Map</tt> instance to a stream.
1693		*
1694		* @serialData The key (Object) and value (Object) for each
1695	<	* key-value mapping represented by the Map, followed by
1695	>	* key-value mapping represented by the Map, followed by
1696		* <tt>null</tt>. The key-value mappings are emitted in key-order
1697		* (as determined by the Comparator, or by the keys' natural
1698		* ordering if no Comparator).
#	Line 1632 | Line 1723 | public class ConcurrentSkipListMap<K,V>
1723		// Reset transients
1724		initialize();
1725
1726	<	/*
1727	<	* This is basically identical to buildFromSorted, but is
1726	>	/*
1727	>	* This is nearly identical to buildFromSorted, but is
1728		* distinct because readObject calls can't be nicely adapted
1729		* as the kind of iterator needed by buildFromSorted. (They
1730		* can be, but doing so requires type cheats and/or creation
#	Line 1643 | Line 1734 | public class ConcurrentSkipListMap<K,V>
1734		HeadIndex<K,V> h = head;
1735		Node<K,V> basepred = h.node;
1736		ArrayList<Index<K,V>> preds = new ArrayList<Index<K,V>>();
1737	<	for (int i = 0; i <= h.level; ++i)
1737	>	for (int i = 0; i <= h.level; ++i)
1738		preds.add(null);
1739		Index<K,V> q = h;
1740		for (int i = h.level; i > 0; --i) {
#	Line 1656 | Line 1747 | public class ConcurrentSkipListMap<K,V>
1747		if (k == null)
1748		break;
1749		Object v = s.readObject();
1750	<	if (v == null)
1750	>	if (v == null)
1751		throw new NullPointerException();
1752		K key = (K) k;
1753		V val = (V) v;
#	Line 1668 | Line 1759 | public class ConcurrentSkipListMap<K,V>
1759		if (j > 0) {
1760		Index<K,V> idx = null;
1761		for (int i = 1; i <= j; ++i) {
1762	<	idx = new Index<K,V>(z, idx);
1763	<	if (i > h.level)
1762	>	idx = new Index<K,V>(z, idx, null);
1763	>	if (i > h.level)
1764		h = new HeadIndex<K,V>(h.node, h, idx, i);
1765
1766		if (i < preds.size()) {
#	Line 1701 | Line 1792 | public class ConcurrentSkipListMap<K,V>
1792
1793		/**
1794		* Returns the value to which this map maps the specified key.  Returns
1795	<	* <tt>null</tt> if the map contains no mapping for this key.
1795	>	* <tt>null</tt> if the map contains no mapping for this key.
1796		*
1797		* @param key key whose associated value is to be returned.
1798		* @return the value to which this map maps the specified key, or
#	Line 1723 | Line 1814 | public class ConcurrentSkipListMap<K,V>
1814		* @param value value to be associated with the specified key.
1815		*
1816		* @return previous value associated with specified key, or <tt>null</tt>
1817	<	*         if there was no mapping for key.
1817	>	*         if there was no mapping for key.
1818		* @throws ClassCastException if the key cannot be compared with the keys
1819		*            currently in the map.
1820		* @throws NullPointerException if the key or value are <tt>null</tt>.
1821		*/
1822		public V put(K key, V value) {
1823	<	if (value == null)
1823	>	if (value == null)
1824		throw new NullPointerException();
1825		return doPut(key, value, false);
1826		}
#	Line 1739 | Line 1830 | public class ConcurrentSkipListMap<K,V>
1830		*
1831		* @param  key key for which mapping should be removed
1832		* @return previous value associated with specified key, or <tt>null</tt>
1833	<	*         if there was no mapping for key.
1833	>	*         if there was no mapping for key.
1834		*
1835		* @throws ClassCastException if the key cannot be compared with the keys
1836		*            currently in the map.
#	Line 1756 | Line 1847 | public class ConcurrentSkipListMap<K,V>
1847		*
1848		* @param value value whose presence in this Map is to be tested.
1849		* @return  <tt>true</tt> if a mapping to <tt>value</tt> exists;
1850	<	*          <tt>false</tt> otherwise.
1850	>	*          <tt>false</tt> otherwise.
1851		* @throws  NullPointerException  if the value is <tt>null</tt>.
1852	<	*/
1852	>	*/
1853		public boolean containsValue(Object value) {
1854	<	if (value == null)
1854	>	if (value == null)
1855		throw new NullPointerException();
1856		for (Node<K,V> n = findFirst(); n != null; n = n.next) {
1857		V v = n.getValidValue();
#	Line 1841 | Line 1932 | public class ConcurrentSkipListMap<K,V>
1932		}
1933
1934		/**
1935	+	* Returns a set view of the keys contained in this map in
1936	+	* descending order.  The set is backed by the map, so changes to
1937	+	* the map are reflected in the set, and vice-versa.  The set
1938	+	* supports element removal, which removes the corresponding
1939	+	* mapping from this map, via the <tt>Iterator.remove</tt>,
1940	+	* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>,
1941	+	* and <tt>clear</tt> operations.  It does not support the
1942	+	* <tt>add</tt> or <tt>addAll</tt> operations.  The view's
1943	+	* <tt>iterator</tt> is a "weakly consistent" iterator that will
1944	+	* never throw {@link java.util.ConcurrentModificationException},
1945	+	* and guarantees to traverse elements as they existed upon
1946	+	* construction of the iterator, and may (but is not guaranteed
1947	+	* to) reflect any modifications subsequent to construction.
1948	+	*
1949	+	* @return a set view of the keys contained in this map.
1950	+	*/
1951	+	public Set<K> descendingKeySet() {
1952	+	/*
1953	+	* Note: Lazy intialization works here and for other views
1954	+	* because view classes are stateless/immutable so it doesn't
1955	+	* matter wrt correctness if more than one is created (which
1956	+	* will only rarely happen).  Even so, the following idiom
1957	+	* conservatively ensures that the method returns the one it
1958	+	* created if it does so, not one created by another racing
1959	+	* thread.
1960	+	*/
1961	+	DescendingKeySet ks = descendingKeySet;
1962	+	return (ks != null) ? ks : (descendingKeySet = new DescendingKeySet());
1963	+	}
1964	+
1965	+	/**
1966		* Returns a collection view of the values contained in this map.
1967		* The collection is backed by the map, so changes to the map are
1968		* reflected in the collection, and vice-versa.  The collection
#	Line 1890 | Line 2012 | public class ConcurrentSkipListMap<K,V>
2012		return (es != null) ? es : (entrySet = new EntrySet());
2013		}
2014
2015	+	/**
2016	+	* Returns a collection view of the mappings contained in this
2017	+	* map, in descending order.  Each element in the returned
2018	+	* collection is a <tt>Map.Entry</tt>.  The collection is backed
2019	+	* by the map, so changes to the map are reflected in the
2020	+	* collection, and vice-versa.  The collection supports element
2021	+	* removal, which removes the corresponding mapping from the map,
2022	+	* via the <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
2023	+	* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
2024	+	* operations.  It does not support the <tt>add</tt> or
2025	+	* <tt>addAll</tt> operations.  The view's <tt>iterator</tt> is a
2026	+	* "weakly consistent" iterator that will never throw {@link
2027	+	* java.util.ConcurrentModificationException}, and guarantees to
2028	+	* traverse elements as they existed upon construction of the
2029	+	* iterator, and may (but is not guaranteed to) reflect any
2030	+	* modifications subsequent to construction. The
2031	+	* <tt>Map.Entry</tt> elements returned by
2032	+	* <tt>iterator.next()</tt> do <em>not</em> support the
2033	+	* <tt>setValue</tt> operation.
2034	+	*
2035	+	* @return a collection view of the mappings contained in this map.
2036	+	*/
2037	+	public Set<Map.Entry<K,V>> descendingEntrySet() {
2038	+	DescendingEntrySet es = descendingEntrySet;
2039	+	return (es != null) ? es : (descendingEntrySet = new DescendingEntrySet());
2040	+	}
2041	+
2042	+	/* ---------------- AbstractMap Overrides -------------- */
2043	+
2044	+	/**
2045	+	* Compares the specified object with this map for equality.
2046	+	* Returns <tt>true</tt> if the given object is also a map and the
2047	+	* two maps represent the same mappings.  More formally, two maps
2048	+	* <tt>t1</tt> and <tt>t2</tt> represent the same mappings if
2049	+	* <tt>t1.keySet().equals(t2.keySet())</tt> and for every key
2050	+	* <tt>k</tt> in <tt>t1.keySet()</tt>, <tt> (t1.get(k)==null ?
2051	+	* t2.get(k)==null : t1.get(k).equals(t2.get(k))) </tt>.  This
2052	+	* operation may return misleading results if either map is
2053	+	* concurrently modified during execution of this method.
2054	+	*
2055	+	* @param o object to be compared for equality with this map.
2056	+	* @return <tt>true</tt> if the specified object is equal to this map.
2057	+	*/
2058	+	public boolean equals(Object o) {
2059	+	if (o == this)
2060	+	return true;
2061	+	if (!(o instanceof Map))
2062	+	return false;
2063	+	Map<K,V> t = (Map<K,V>) o;
2064	+	try {
2065	+	return (containsAllMappings(this, t) &&
2066	+	containsAllMappings(t, this));
2067	+	} catch (ClassCastException unused) {
2068	+	return false;
2069	+	} catch (NullPointerException unused) {
2070	+	return false;
2071	+	}
2072	+	}
2073	+
2074	+	/**
2075	+	* Helper for equals -- check for containment, avoiding nulls.
2076	+	*/
2077	+	static <K,V> boolean containsAllMappings(Map<K,V> a, Map<K,V> b) {
2078	+	Iterator<Entry<K,V>> it = b.entrySet().iterator();
2079	+	while (it.hasNext()) {
2080	+	Entry<K,V> e = it.next();
2081	+	Object k = e.getKey();
2082	+	Object v = e.getValue();
2083	+	if (k == null || v == null || !v.equals(a.get(k)))
2084	+	return false;
2085	+	}
2086	+	return true;
2087	+	}
2088	+
2089		/* ------ ConcurrentMap API methods ------ */
2090
2091		/**
#	Line 1897 | Line 2093 | public class ConcurrentSkipListMap<K,V>
2093		* with a value, associate it with the given value.
2094		* This is equivalent to
2095		* <pre>
2096	<	*   if (!map.containsKey(key))
2096	>	*   if (!map.containsKey(key))
2097		*      return map.put(key, value);
2098		*   else
2099		*      return map.get(key);
2100		* </pre>
2101	<	* Except that the action is performed atomically.
2101	>	* except that the action is performed atomically.
2102		* @param key key with which the specified value is to be associated.
2103		* @param value value to be associated with the specified key.
2104		* @return previous value associated with specified key, or <tt>null</tt>
2105	<	*         if there was no mapping for key.
2105	>	*         if there was no mapping for key.
2106		*
2107		* @throws ClassCastException if the key cannot be compared with the keys
2108		*            currently in the map.
2109		* @throws NullPointerException if the key or value are <tt>null</tt>.
2110		*/
2111		public V putIfAbsent(K key, V value) {
2112	<	if (value == null)
2112	>	if (value == null)
2113		throw new NullPointerException();
2114		return doPut(key, value, true);
2115		}
#	Line 1921 | Line 2117 | public class ConcurrentSkipListMap<K,V>
2117		/**
2118		* Remove entry for key only if currently mapped to given value.
2119		* Acts as
2120	<	* <pre>
2120	>	* <pre>
2121		*  if ((map.containsKey(key) && map.get(key).equals(value)) {
2122		*     map.remove(key);
2123		*     return true;
#	Line 1936 | Line 2132 | public class ConcurrentSkipListMap<K,V>
2132		* @throws NullPointerException if the key or value are <tt>null</tt>.
2133		*/
2134		public boolean remove(Object key, Object value) {
2135	<	if (value == null)
2135	>	if (value == null)
2136		throw new NullPointerException();
2137		return doRemove(key, value) != null;
2138		}
#	Line 1944 | Line 2140 | public class ConcurrentSkipListMap<K,V>
2140		/**
2141		* Replace entry for key only if currently mapped to given value.
2142		* Acts as
2143	<	* <pre>
2143	>	* <pre>
2144		*  if ((map.containsKey(key) && map.get(key).equals(oldValue)) {
2145		*     map.put(key, newValue);
2146		*     return true;
#	Line 1961 | Line 2157 | public class ConcurrentSkipListMap<K,V>
2157		* <tt>null</tt>.
2158		*/
2159		public boolean replace(K key, V oldValue, V newValue) {
2160	<	if (oldValue == null || newValue == null)
2160	>	if (oldValue == null || newValue == null)
2161		throw new NullPointerException();
2162		Comparable<K> k = comparable(key);
2163		for (;;) {
#	Line 1981 | Line 2177 | public class ConcurrentSkipListMap<K,V>
2177		/**
2178		* Replace entry for key only if currently mapped to some value.
2179		* Acts as
2180	<	* <pre>
2180	>	* <pre>
2181		*  if ((map.containsKey(key)) {
2182		*     return map.put(key, value);
2183		* } else return null;
#	Line 1990 | Line 2186 | public class ConcurrentSkipListMap<K,V>
2186		* @param key key with which the specified value is associated.
2187		* @param value value to be associated with the specified key.
2188		* @return previous value associated with specified key, or <tt>null</tt>
2189	<	*         if there was no mapping for key.
2189	>	*         if there was no mapping for key.
2190		* @throws ClassCastException if the key cannot be compared with the keys
2191		*            currently in the map.
2192		* @throws NullPointerException if the key or value are <tt>null</tt>.
2193		*/
2194		public V replace(K key, V value) {
2195	<	if (value == null)
2195	>	if (value == null)
2196		throw new NullPointerException();
2197		Comparable<K> k = comparable(key);
2198		for (;;) {
#	Line 2028 | Line 2224 | public class ConcurrentSkipListMap<K,V>
2224		* @return the first (lowest) key currently in this map.
2225		* @throws    NoSuchElementException Map is empty.
2226		*/
2227	<	public K firstKey() {
2227	>	public K firstKey() {
2228		Node<K,V> n = findFirst();
2229		if (n == null)
2230		throw new NoSuchElementException();
#	Line 2076 | Line 2272 | public class ConcurrentSkipListMap<K,V>
2272		}
2273
2274		/**
2275	<	* Returns a view of the portion of this map whose keys are strictly less
2276	<	* than <tt>toKey</tt>.  The returned sorted map is backed by this map, so
2277	<	* changes in the returned sorted map are reflected in this map, and
2278	<	* vice-versa.
2275	>	* Returns a view of the portion of this map whose keys are
2276	>	* strictly less than <tt>toKey</tt>.  The returned sorted map is
2277	>	* backed by this map, so changes in the returned sorted map are
2278	>	* reflected in this map, and vice-versa.
2279		* @param toKey high endpoint (exclusive) of the headMap.
2280	<	* @return a view of the portion of this map whose keys are strictly
2281	<	*                less than <tt>toKey</tt>.
2280	>	* @return a view of the portion of this map whose keys are
2281	>	* strictly less than <tt>toKey</tt>.
2282		*
2283		* @throws ClassCastException if <tt>toKey</tt> is not compatible
2284	<	*         with this map's comparator (or, if the map has no comparator,
2285	<	*         if <tt>toKey</tt> does not implement <tt>Comparable</tt>).
2284	>	* with this map's comparator (or, if the map has no comparator,
2285	>	* if <tt>toKey</tt> does not implement <tt>Comparable</tt>).
2286		* @throws NullPointerException if <tt>toKey</tt> is <tt>null</tt>.
2287		*/
2288		public ConcurrentNavigableMap<K,V> headMap(K toKey) {
#	Line 2101 | Line 2297 | public class ConcurrentSkipListMap<K,V>
2297		* map is backed by this map, so changes in the returned sorted
2298		* map are reflected in this map, and vice-versa.
2299		* @param fromKey low endpoint (inclusive) of the tailMap.
2300	<	* @return a view of the portion of this map whose keys are greater
2301	<	*                than or equal to <tt>fromKey</tt>.
2302	<	* @throws ClassCastException if <tt>fromKey</tt> is not compatible
2303	<	*         with this map's comparator (or, if the map has no comparator,
2304	<	*         if <tt>fromKey</tt> does not implement <tt>Comparable</tt>).
2300	>	* @return a view of the portion of this map whose keys are
2301	>	* greater than or equal to <tt>fromKey</tt>.
2302	>	* @throws ClassCastException if <tt>fromKey</tt> is not
2303	>	* compatible with this map's comparator (or, if the map has no
2304	>	* comparator, if <tt>fromKey</tt> does not implement
2305	>	* <tt>Comparable</tt>).
2306		* @throws NullPointerException if <tt>fromKey</tt> is <tt>null</tt>.
2307		*/
2308		public ConcurrentNavigableMap<K,V>  tailMap(K fromKey) {
#	Line 2118 | Line 2315 | public class ConcurrentSkipListMap<K,V>
2315
2316		/**
2317		* Returns a key-value mapping associated with the least key
2318	<	* greater than or equal to the given key, or <tt>null</tt> if there is
2319	<	* no such entry. The returned entry does <em>not</em> support
2320	<	* the <tt>Entry.setValue</tt> method.
2321	<	*
2318	>	* greater than or equal to the given key, or <tt>null</tt> if
2319	>	* there is no such entry. The returned entry does <em>not</em>
2320	>	* support the <tt>Entry.setValue</tt> method.
2321	>	*
2322		* @param key the key.
2323	<	* @return an Entry associated with ceiling of given key, or <tt>null</tt>
2324	<	* if there is no such Entry.
2325	<	* @throws ClassCastException if key cannot be compared with the keys
2326	<	*            currently in the map.
2323	>	* @return an Entry associated with ceiling of given key, or
2324	>	* <tt>null</tt> if there is no such Entry.
2325	>	* @throws ClassCastException if key cannot be compared with the
2326	>	* keys currently in the map.
2327		* @throws NullPointerException if key is <tt>null</tt>.
2328		*/
2329		public Map.Entry<K,V> ceilingEntry(K key) {
#	Line 2134 | Line 2331 | public class ConcurrentSkipListMap<K,V>
2331		}
2332
2333		/**
2334	+	* Returns least key greater than or equal to the given key, or
2335	+	* <tt>null</tt> if there is no such key.
2336	+	*
2337	+	* @param key the key.
2338	+	* @return the ceiling key, or <tt>null</tt>
2339	+	* if there is no such key.
2340	+	* @throws ClassCastException if key cannot be compared with the keys
2341	+	*            currently in the map.
2342	+	* @throws NullPointerException if key is <tt>null</tt>.
2343	+	*/
2344	+	public K ceilingKey(K key) {
2345	+	Node<K,V> n = findNear(key, GT|EQ);
2346	+	return (n == null)? null : n.key;
2347	+	}
2348	+
2349	+	/**
2350		* Returns a key-value mapping associated with the greatest
2351		* key strictly less than the given key, or <tt>null</tt> if there is no
2352		* such entry. The returned entry does <em>not</em> support
2353		* the <tt>Entry.setValue</tt> method.
2354	<	*
2354	>	*
2355		* @param key the key.
2356		* @return an Entry with greatest key less than the given
2357		* key, or <tt>null</tt> if there is no such Entry.
#	Line 2151 | Line 2364 | public class ConcurrentSkipListMap<K,V>
2364		}
2365
2366		/**
2367	<	* Returns a key-value mapping associated with the greatest
2368	<	* key less than or equal to the given key, or <tt>null</tt> if there is no
2369	<	* such entry. The returned entry does <em>not</em> support
2367	>	* Returns the greatest key strictly less than the given key, or
2368	>	* <tt>null</tt> if there is no such key.
2369	>	*
2370	>	* @param key the key.
2371	>	* @return the greatest key less than the given
2372	>	* key, or <tt>null</tt> if there is no such key.
2373	>	* @throws ClassCastException if key cannot be compared with the keys
2374	>	*            currently in the map.
2375	>	* @throws NullPointerException if key is <tt>null</tt>.
2376	>	*/
2377	>	public K lowerKey(K key) {
2378	>	Node<K,V> n = findNear(key, LT);
2379	>	return (n == null)? null : n.key;
2380	>	}
2381	>
2382	>	/**
2383	>	* Returns a key-value mapping associated with the greatest key
2384	>	* less than or equal to the given key, or <tt>null</tt> if there
2385	>	* is no such entry. The returned entry does <em>not</em> support
2386		* the <tt>Entry.setValue</tt> method.
2387	<	*
2387	>	*
2388		* @param key the key.
2389		* @return an Entry associated with floor of given key, or <tt>null</tt>
2390		* if there is no such Entry.
#	Line 2168 | Line 2397 | public class ConcurrentSkipListMap<K,V>
2397		}
2398
2399		/**
2400	<	* Returns a key-value mapping associated with the least
2401	<	* key strictly greater than the given key, or <tt>null</tt> if there is no
2402	<	* such entry. The returned entry does <em>not</em> support
2400	>	* Returns the greatest key
2401	>	* less than or equal to the given key, or <tt>null</tt> if there
2402	>	* is no such key.
2403	>	*
2404	>	* @param key the key.
2405	>	* @return the floor of given key, or <tt>null</tt> if there is no
2406	>	* such key.
2407	>	* @throws ClassCastException if key cannot be compared with the keys
2408	>	*            currently in the map.
2409	>	* @throws NullPointerException if key is <tt>null</tt>.
2410	>	*/
2411	>	public K floorKey(K key) {
2412	>	Node<K,V> n = findNear(key, LT|EQ);
2413	>	return (n == null)? null : n.key;
2414	>	}
2415	>
2416	>	/**
2417	>	* Returns a key-value mapping associated with the least key
2418	>	* strictly greater than the given key, or <tt>null</tt> if there
2419	>	* is no such entry. The returned entry does <em>not</em> support
2420		* the <tt>Entry.setValue</tt> method.
2421	<	*
2421	>	*
2422		* @param key the key.
2423		* @return an Entry with least key greater than the given key, or
2424		* <tt>null</tt> if there is no such Entry.
#	Line 2185 | Line 2431 | public class ConcurrentSkipListMap<K,V>
2431		}
2432
2433		/**
2434	+	* Returns the least key strictly greater than the given key, or
2435	+	* <tt>null</tt> if there is no such key.
2436	+	*
2437	+	* @param key the key.
2438	+	* @return the least key greater than the given key, or
2439	+	* <tt>null</tt> if there is no such key.
2440	+	* @throws ClassCastException if key cannot be compared with the keys
2441	+	*            currently in the map.
2442	+	* @throws NullPointerException if key is <tt>null</tt>.
2443	+	*/
2444	+	public K higherKey(K key) {
2445	+	Node<K,V> n = findNear(key, GT);
2446	+	return (n == null)? null : n.key;
2447	+	}
2448	+
2449	+	/**
2450		* Returns a key-value mapping associated with the least
2451		* key in this map, or <tt>null</tt> if the map is empty.
2452		* The returned entry does <em>not</em> support
2453		* the <tt>Entry.setValue</tt> method.
2454	<	*
2455	<	* @return an Entry with least key, or <tt>null</tt>
2454	>	*
2455	>	* @return an Entry with least key, or <tt>null</tt>
2456		* if the map is empty.
2457		*/
2458		public Map.Entry<K,V> firstEntry() {
2459		for (;;) {
2460		Node<K,V> n = findFirst();
2461	<	if (n == null)
2461	>	if (n == null)
2462		return null;
2463		SnapshotEntry<K,V> e = n.createSnapshot();
2464		if (e != null)
#	Line 2209 | Line 2471 | public class ConcurrentSkipListMap<K,V>
2471		* key in this map, or <tt>null</tt> if the map is empty.
2472		* The returned entry does <em>not</em> support
2473		* the <tt>Entry.setValue</tt> method.
2474	<	*
2474	>	*
2475		* @return an Entry with greatest key, or <tt>null</tt>
2476		* if the map is empty.
2477		*/
2478		public Map.Entry<K,V> lastEntry() {
2479		for (;;) {
2480		Node<K,V> n = findLast();
2481	<	if (n == null)
2481	>	if (n == null)
2482		return null;
2483		SnapshotEntry<K,V> e = n.createSnapshot();
2484		if (e != null)
#	Line 2229 | Line 2491 | public class ConcurrentSkipListMap<K,V>
2491		* the least key in this map, or <tt>null</tt> if the map is empty.
2492		* The returned entry does <em>not</em> support
2493		* the <tt>Entry.setValue</tt> method.
2494	<	*
2494	>	*
2495		* @return the removed first entry of this map, or <tt>null</tt>
2496		* if the map is empty.
2497		*/
2498		public Map.Entry<K,V> pollFirstEntry() {
2499	<	return doRemoveFirstEntry();
2499	>	return (SnapshotEntry<K,V>)doRemoveFirst(false);
2500		}
2501
2502		/**
#	Line 2242 | Line 2504 | public class ConcurrentSkipListMap<K,V>
2504		* the greatest key in this map, or <tt>null</tt> if the map is empty.
2505		* The returned entry does <em>not</em> support
2506		* the <tt>Entry.setValue</tt> method.
2507	<	*
2507	>	*
2508		* @return the removed last entry of this map, or <tt>null</tt>
2509		* if the map is empty.
2510		*/
2511		public Map.Entry<K,V> pollLastEntry() {
2512	<	return doRemoveLastEntry();
2512	>	return (SnapshotEntry<K,V>)doRemoveLast(false);
2513		}
2514
2515	+
2516		/* ---------------- Iterators -------------- */
2517
2518		/**
2519	<	* Base of iterator classes.
2520	<	* (Six kinds: {key, value, entry} X {map, submap})
2519	>	* Base of ten kinds of iterator classes:
2520	>	*   ascending:  {map, submap} X {key, value, entry}
2521	>	*   descending: {map, submap} X {key, entry}
2522		*/
2523	<	abstract class ConcurrentSkipListMapIterator {
2523	>	abstract class Iter {
2524		/** the last node returned by next() */
2525		Node<K,V> last;
2526		/** the next node to return from next(); */
2527		Node<K,V> next;
2528	<	/** Cache of next value field to maintain weak consistency */
2529	<	Object nextValue;
2528	>	/** Cache of next value field to maintain weak consistency */
2529	>	Object nextValue;
2530
2531	<	/** Create normal iterator for entire range  */
2532	<	ConcurrentSkipListMapIterator() {
2531	>	Iter() {}
2532	>
2533	>	public final boolean hasNext() {
2534	>	return next != null;
2535	>	}
2536	>
2537	>	/** initialize ascending iterator for entire range  */
2538	>	final void initAscending() {
2539		for (;;) {
2540	<	next = findFirst();
2540	>	next = findFirst();
2541		if (next == null)
2542		break;
2543		nextValue = next.value;
#	Line 2276 | Line 2546 | public class ConcurrentSkipListMap<K,V>
2546		}
2547		}
2548
2549	<	/**
2550	<	* Create a submap iterator starting at given least key, or
2551	<	* first node if least is <tt>null</tt>, but not greater or equal to
2552	<	* fence, or end if fence is <tt>null</tt>.
2549	>	/**
2550	>	* initialize ascending iterator starting at given least key,
2551	>	* or first node if least is <tt>null</tt>, but not greater or
2552	>	* equal to fence, or end if fence is <tt>null</tt>.
2553		*/
2554	<	ConcurrentSkipListMapIterator(K least, K fence) {
2554	>	final void initAscending(K least, K fence) {
2555		for (;;) {
2556	<	next = findCeiling(least);
2556	>	next = findCeiling(least);
2557		if (next == null)
2558		break;
2559		nextValue = next.value;
#	Line 2296 | Line 2566 | public class ConcurrentSkipListMap<K,V>
2566		}
2567		}
2568		}
2569	+	/** advance next to higher entry */
2570	+	final void ascend() {
2571	+	if ((last = next) == null)
2572	+	throw new NoSuchElementException();
2573	+	for (;;) {
2574	+	next = next.next;
2575	+	if (next == null)
2576	+	break;
2577	+	nextValue = next.value;
2578	+	if (nextValue != null && nextValue != next)
2579	+	break;
2580	+	}
2581	+	}
2582
2583	<	public final boolean hasNext() {
2584	<	return next != null;
2583	>	/**
2584	>	* Version of ascend for submaps to stop at fence
2585	>	*/
2586	>	final void ascend(K fence) {
2587	>	if ((last = next) == null)
2588	>	throw new NoSuchElementException();
2589	>	for (;;) {
2590	>	next = next.next;
2591	>	if (next == null)
2592	>	break;
2593	>	nextValue = next.value;
2594	>	if (nextValue != null && nextValue != next) {
2595	>	if (fence != null && compare(fence, next.key) <= 0) {
2596	>	next = null;
2597	>	nextValue = null;
2598	>	}
2599	>	break;
2600	>	}
2601	>	}
2602		}
2603
2604	<	final void advance() {
2604	>	/** initialize descending iterator for entire range  */
2605	>	final void initDescending() {
2606	>	for (;;) {
2607	>	next = findLast();
2608	>	if (next == null)
2609	>	break;
2610	>	nextValue = next.value;
2611	>	if (nextValue != null && nextValue != next)
2612	>	break;
2613	>	}
2614	>	}
2615	>
2616	>	/**
2617	>	* initialize descending iterator starting at key less
2618	>	* than or equal to given fence key, or
2619	>	* last node if fence is <tt>null</tt>, but not less than
2620	>	* least, or beginning if lest is <tt>null</tt>.
2621	>	*/
2622	>	final void initDescending(K least, K fence) {
2623	>	for (;;) {
2624	>	next = findLower(fence);
2625	>	if (next == null)
2626	>	break;
2627	>	nextValue = next.value;
2628	>	if (nextValue != null && nextValue != next) {
2629	>	if (least != null && compare(least, next.key) > 0) {
2630	>	next = null;
2631	>	nextValue = null;
2632	>	}
2633	>	break;
2634	>	}
2635	>	}
2636	>	}
2637	>
2638	>	/** advance next to lower entry */
2639	>	final void descend() {
2640		if ((last = next) == null)
2641		throw new NoSuchElementException();
2642	+	K k = last.key;
2643		for (;;) {
2644	<	next = next.next;
2644	>	next = findNear(k, LT);
2645		if (next == null)
2646		break;
2647		nextValue = next.value;
#	Line 2315 | Line 2651 | public class ConcurrentSkipListMap<K,V>
2651		}
2652
2653		/**
2654	<	* Version of advance for submaps to stop at fence
2654	>	* Version of descend for submaps to stop at least
2655		*/
2656	<	final void advance(K fence) {
2656	>	final void descend(K least) {
2657		if ((last = next) == null)
2658		throw new NoSuchElementException();
2659	+	K k = last.key;
2660		for (;;) {
2661	<	next = next.next;
2661	>	next = findNear(k, LT);
2662		if (next == null)
2663		break;
2664		nextValue = next.value;
2665		if (nextValue != null && nextValue != next) {
2666	<	if (fence != null && compare(fence, next.key) <= 0) {
2666	>	if (least != null && compare(least, next.key) > 0) {
2667		next = null;
2668		nextValue = null;
2669		}
#	Line 2343 | Line 2680 | public class ConcurrentSkipListMap<K,V>
2680		// unlink from here. Using remove is fast enough.
2681		ConcurrentSkipListMap.this.remove(l.key);
2682		}
2683	+
2684		}
2685
2686	<	final class ValueIterator extends ConcurrentSkipListMapIterator
2687	<	implements Iterator<V> {
2688	<	public V next() {
2686	>	final class ValueIterator extends Iter implements Iterator<V> {
2687	>	ValueIterator() {
2688	>	initAscending();
2689	>	}
2690	>	public V next() {
2691		Object v = nextValue;
2692	<	advance();
2692	>	ascend();
2693		return (V)v;
2694		}
2695		}
2696
2697	<	final class KeyIterator extends ConcurrentSkipListMapIterator
2698	<	implements Iterator<K> {
2699	<	public K next() {
2697	>	final class KeyIterator extends Iter implements Iterator<K> {
2698	>	KeyIterator() {
2699	>	initAscending();
2700	>	}
2701	>	public K next() {
2702		Node<K,V> n = next;
2703	<	advance();
2703	>	ascend();
2704	>	return n.key;
2705	>	}
2706	>	}
2707	>
2708	>	class SubMapValueIterator extends Iter implements Iterator<V> {
2709	>	final K fence;
2710	>	SubMapValueIterator(K least, K fence) {
2711	>	initAscending(least, fence);
2712	>	this.fence = fence;
2713	>	}
2714	>
2715	>	public V next() {
2716	>	Object v = nextValue;
2717	>	ascend(fence);
2718	>	return (V)v;
2719	>	}
2720	>	}
2721	>
2722	>	final class SubMapKeyIterator extends Iter implements Iterator<K> {
2723	>	final K fence;
2724	>	SubMapKeyIterator(K least, K fence) {
2725	>	initAscending(least, fence);
2726	>	this.fence = fence;
2727	>	}
2728	>
2729	>	public K next() {
2730	>	Node<K,V> n = next;
2731	>	ascend(fence);
2732	>	return n.key;
2733	>	}
2734	>	}
2735	>
2736	>	final class DescendingKeyIterator extends Iter implements Iterator<K> {
2737	>	DescendingKeyIterator() {
2738	>	initDescending();
2739	>	}
2740	>	public K next() {
2741	>	Node<K,V> n = next;
2742	>	descend();
2743	>	return n.key;
2744	>	}
2745	>	}
2746	>
2747	>	final class DescendingSubMapKeyIterator extends Iter implements Iterator<K> {
2748	>	final K least;
2749	>	DescendingSubMapKeyIterator(K least, K fence) {
2750	>	initDescending(least, fence);
2751	>	this.least = least;
2752	>	}
2753	>
2754	>	public K next() {
2755	>	Node<K,V> n = next;
2756	>	descend(least);
2757		return n.key;
2758		}
2759		}
#	Line 2368 | Line 2763 | public class ConcurrentSkipListMap<K,V>
2763		* elsewhere of using the iterator itself to represent entries,
2764		* thus avoiding having to create entry objects in next().
2765		*/
2766	<	class EntryIterator extends ConcurrentSkipListMapIterator
2372	<	implements Map.Entry<K,V>, Iterator<Map.Entry<K,V>>  {
2766	>	abstract class EntryIter extends Iter implements Map.Entry<K,V> {
2767		/** Cache of last value returned */
2768		Object lastValue;
2769
2770	<	EntryIterator() {
2377	<	super();
2378	<	}
2379	<
2380	<	EntryIterator(K least, K fence) {
2381	<	super(least, fence);
2382	<	}
2383	<
2384	<	public Map.Entry<K,V> next() {
2385	<	lastValue = nextValue;
2386	<	advance();
2387	<	return this;
2770	>	EntryIter() {
2771		}
2772
2773		public K getKey() {
#	Line 2398 | Line 2781 | public class ConcurrentSkipListMap<K,V>
2781		Object v = lastValue;
2782		if (last == null || v == null)
2783		throw new IllegalStateException();
2784	<	return (V)v;
2784	>	return (V)v;
2785		}
2786
2787		public V setValue(V value) {
#	Line 2427 | Line 2810 | public class ConcurrentSkipListMap<K,V>
2810		// If not acting as entry, just use default.
2811		if (last == null)
2812		return super.toString();
2813	<	return getKey() + "=" + getValue();
2813	>	return getKey() + "=" + getValue();
2814		}
2815		}
2816
2817	<	/**
2818	<	* Submap iterators start at given starting point at beginning of
2819	<	* submap range, and advance until they are at end of range.
2820	<	*/
2821	<	class SubMapEntryIterator extends EntryIterator {
2817	>	final class EntryIterator extends EntryIter
2818	>	implements Iterator<Map.Entry<K,V>> {
2819	>	EntryIterator() {
2820	>	initAscending();
2821	>	}
2822	>	public Map.Entry<K,V> next() {
2823	>	lastValue = nextValue;
2824	>	ascend();
2825	>	return this;
2826	>	}
2827	>	}
2828	>
2829	>	final class SubMapEntryIterator extends EntryIter
2830	>	implements Iterator<Map.Entry<K,V>> {
2831		final K fence;
2832		SubMapEntryIterator(K least, K fence) {
2833	<	super(least, fence);
2833	>	initAscending(least, fence);
2834		this.fence = fence;
2835		}
2836
2837	<	public Map.Entry<K,V> next() {
2837	>	public Map.Entry<K,V> next() {
2838		lastValue = nextValue;
2839	<	advance(fence);
2839	>	ascend(fence);
2840		return this;
2841		}
2842		}
2843
2844	<	class SubMapValueIterator extends ConcurrentSkipListMapIterator
2845	<	implements Iterator<V> {
2846	<	final K fence;
2847	<	SubMapValueIterator(K least, K fence) {
2456	<	super(least, fence);
2457	<	this.fence = fence;
2844	>	final class DescendingEntryIterator extends EntryIter
2845	>	implements Iterator<Map.Entry<K,V>>  {
2846	>	DescendingEntryIterator() {
2847	>	initDescending();
2848		}
2849	<
2850	<	public V next() {
2851	<	Object v = nextValue;
2852	<	advance(fence);
2463	<	return (V)v;
2849	>	public Map.Entry<K,V> next() {
2850	>	lastValue = nextValue;
2851	>	descend();
2852	>	return this;
2853		}
2854		}
2855
2856	<	class SubMapKeyIterator extends ConcurrentSkipListMapIterator
2857	<	implements Iterator<K> {
2858	<	final K fence;
2859	<	SubMapKeyIterator(K least, K fence) {
2860	<	super(least, fence);
2861	<	this.fence = fence;
2856	>	final class DescendingSubMapEntryIterator extends EntryIter
2857	>	implements Iterator<Map.Entry<K,V>>  {
2858	>	final K least;
2859	>	DescendingSubMapEntryIterator(K least, K fence) {
2860	>	initDescending(least, fence);
2861	>	this.least = least;
2862		}
2863
2864	<	public K next() {
2865	<	Node<K,V> n = next;
2866	<	advance(fence);
2867	<	return n.key;
2864	>	public Map.Entry<K,V> next() {
2865	>	lastValue = nextValue;
2866	>	descend(least);
2867	>	return this;
2868		}
2869		}
2870
2482	–	/* ---------------- Utilities for views, sets, submaps -------------- */
2483	–
2871		// Factory methods for iterators needed by submaps and/or
2872		// ConcurrentSkipListSet
2873
#	Line 2488 | Line 2875 | public class ConcurrentSkipListMap<K,V>
2875		return new KeyIterator();
2876		}
2877
2878	<	SubMapEntryIterator subMapEntryIterator(K least, K fence) {
2879	<	return new SubMapEntryIterator(least, fence);
2493	<	}
2494	<
2495	<	SubMapKeyIterator subMapKeyIterator(K least, K fence) {
2496	<	return new SubMapKeyIterator(least, fence);
2497	<	}
2498	<
2499	<	SubMapValueIterator subMapValueIterator(K least, K fence) {
2500	<	return new SubMapValueIterator(least, fence);
2501	<	}
2502	<
2503	<
2504	<	/**
2505	<	* Version of remove with boolean return. Needed by
2506	<	* view classes and ConcurrentSkipListSet
2507	<	*/
2508	<	boolean removep(Object key) {
2509	<	return doRemove(key, null) != null;
2510	<	}
2511	<
2512	<	/**
2513	<	* Return SnapshotEntry for results of findNear ofter screening
2514	<	* to ensure result is in given range. Needed by submaps.
2515	<	* @param kkey the key
2516	<	* @param rel the relation -- OR'ed combination of EQ, LT, GT
2517	<	* @param least minimum allowed key value
2518	<	* @param fence key greater than maximum allowed key value
2519	<	* @return Entry fitting relation, or <tt>null</tt> if no such
2520	<	*/
2521	<	SnapshotEntry<K,V> getNear(K kkey, int rel, K least, K fence) {
2522	<	K key = kkey;
2523	<	// Don't return keys less than least
2524	<	if ((rel & LT) == 0) {
2525	<	if (compare(key, least) < 0) {
2526	<	key = least;
2527	<	rel = rel | EQ;
2528	<	}
2529	<	}
2530	<
2531	<	for (;;) {
2532	<	Node<K,V> n = findNear(key, rel);
2533	<	if (n == null || !inHalfOpenRange(n.key, least, fence))
2534	<	return null;
2535	<	SnapshotEntry<K,V> e = n.createSnapshot();
2536	<	if (e != null)
2537	<	return e;
2538	<	}
2539	<	}
2540	<
2541	<	// Methods expanding out relational operations for submaps
2542	<
2543	<	/**
2544	<	* Return ceiling, or first node if key is <tt>null</tt>
2545	<	*/
2546	<	Node<K,V> findCeiling(K key) {
2547	<	return (key == null)? findFirst() : findNear(key, GT|EQ);
2548	<	}
2549	<
2550	<	/**
2551	<	* Return lower node, or last node if key is <tt>null</tt>
2552	<	*/
2553	<	Node<K,V> findLower(K key) {
2554	<	return (key == null)? findLast() : findNear(key, LT);
2555	<	}
2556	<
2557	<	/**
2558	<	* Find and remove least element of subrange.
2559	<	*/
2560	<	SnapshotEntry<K,V> removeFirstEntryOfSubrange(K least, K fence) {
2561	<	for (;;) {
2562	<	Node<K,V> n = findCeiling(least);
2563	<	if (n == null)
2564	<	return null;
2565	<	K k = n.key;
2566	<	if (fence != null && compare(k, fence) >= 0)
2567	<	return null;
2568	<	V v = doRemove(k, null);
2569	<	if (v != null)
2570	<	return new SnapshotEntry<K,V>(k,v);
2571	<	}
2572	<	}
2573	<
2574	<
2575	<	/**
2576	<	* Find and remove greatest element of subrange.
2577	<	*/
2578	<	SnapshotEntry<K,V> removeLastEntryOfSubrange(K least, K fence) {
2579	<	for (;;) {
2580	<	Node<K,V> n = findLower(fence);
2581	<	if (n == null)
2582	<	return null;
2583	<	K k = n.key;
2584	<	if (least != null && compare(k, least) < 0)
2585	<	return null;
2586	<	V v = doRemove(k, null);
2587	<	if (v != null)
2588	<	return new SnapshotEntry<K,V>(k,v);
2589	<	}
2590	<	}
2591	<
2592	<
2593	<	SnapshotEntry<K,V> getCeiling(K key, K least, K fence) {
2594	<	return getNear(key, GT|EQ, least, fence);
2595	<	}
2596	<
2597	<	SnapshotEntry<K,V> getLower(K key, K least, K fence) {
2598	<	return getNear(key, LT, least, fence);
2599	<	}
2600	<
2601	<	SnapshotEntry<K,V> getFloor(K key, K least, K fence) {
2602	<	return getNear(key, LT|EQ, least, fence);
2878	>	Iterator<K> descendingKeyIterator() {
2879	>	return new DescendingKeyIterator();
2880		}
2881
2882	<	SnapshotEntry<K,V> getHigher(K key, K least, K fence) {
2883	<	return getNear(key, GT, least, fence);
2607	<	}
2608	<
2609	<	// Key-returning relational methods for ConcurrentSkipListSet
2610	<
2611	<	K ceilingKey(K key) {
2612	<	Node<K,V> n = findNear(key, GT|EQ);
2613	<	return (n == null)? null : n.key;
2882	>	SubMapEntryIterator subMapEntryIterator(K least, K fence) {
2883	>	return new SubMapEntryIterator(least, fence);
2884		}
2885
2886	<	K lowerKey(K key) {
2887	<	Node<K,V> n = findNear(key, LT);
2618	<	return (n == null)? null : n.key;
2886	>	DescendingSubMapEntryIterator descendingSubMapEntryIterator(K least, K fence) {
2887	>	return new DescendingSubMapEntryIterator(least, fence);
2888		}
2889
2890	<	K floorKey(K key) {
2891	<	Node<K,V> n = findNear(key, LT|EQ);
2623	<	return (n == null)? null : n.key;
2624	<	}
2625	<
2626	<	K higherKey(K key) {
2627	<	Node<K,V> n = findNear(key, GT);
2628	<	return (n == null)? null : n.key;
2890	>	SubMapKeyIterator subMapKeyIterator(K least, K fence) {
2891	>	return new SubMapKeyIterator(least, fence);
2892		}
2893
2894	<	K lowestKey() {
2895	<	Node<K,V> n = findFirst();
2633	<	return (n == null)? null : n.key;
2894	>	DescendingSubMapKeyIterator descendingSubMapKeyIterator(K least, K fence) {
2895	>	return new DescendingSubMapKeyIterator(least, fence);
2896		}
2897
2898	<	K highestKey() {
2899	<	Node<K,V> n = findLast();
2638	<	return (n == null)? null : n.key;
2898	>	SubMapValueIterator subMapValueIterator(K least, K fence) {
2899	>	return new SubMapValueIterator(least, fence);
2900		}
2901
2902		/* ---------------- Views -------------- */
2903
2904	<	final class KeySet extends AbstractSet<K> {
2904	>	class KeySet extends AbstractSet<K> {
2905		public Iterator<K> iterator() {
2906		return new KeyIterator();
2907		}
#	Line 2673 | Line 2934 | public class ConcurrentSkipListMap<K,V>
2934		}
2935		}
2936
2937	+	class DescendingKeySet extends KeySet {
2938	+	public Iterator<K> iterator() {
2939	+	return new DescendingKeyIterator();
2940	+	}
2941	+	}
2942
2943		final class Values extends AbstractCollection<V> {
2944		public Iterator<V> iterator() {
#	Line 2704 | Line 2970 | public class ConcurrentSkipListMap<K,V>
2970		}
2971		}
2972
2973	<	final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
2973	>	class EntrySet extends AbstractSet<Map.Entry<K,V>> {
2974		public Iterator<Map.Entry<K,V>> iterator() {
2975		return new EntryIterator();
2976		}
#	Line 2719 | Line 2985 | public class ConcurrentSkipListMap<K,V>
2985		if (!(o instanceof Map.Entry))
2986		return false;
2987		Map.Entry<K,V> e = (Map.Entry<K,V>)o;
2988	<	return ConcurrentSkipListMap.this.remove(e.getKey(), e.getValue());
2988	>	return ConcurrentSkipListMap.this.remove(e.getKey(),
2989	>	e.getValue());
2990		}
2991		public boolean isEmpty() {
2992		return ConcurrentSkipListMap.this.isEmpty();
#	Line 2733 | Line 3000 | public class ConcurrentSkipListMap<K,V>
3000
3001		public Object[] toArray() {
3002		Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>();
3003	<	for (Node<K,V> n = findFirst(); n != null; n = n.next) {
3004	<	Map.Entry<K,V> e = n.createSnapshot();
2738	<	if (e != null)
2739	<	c.add(e);
2740	<	}
3003	>	for (Map.Entry e : this)
3004	>	c.add(new SnapshotEntry(e.getKey(), e.getValue()));
3005		return c.toArray();
3006		}
3007		public <T> T[] toArray(T[] a) {
3008		Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>();
3009	<	for (Node<K,V> n = findFirst(); n != null; n = n.next) {
3010	<	Map.Entry<K,V> e = n.createSnapshot();
2747	<	if (e != null)
2748	<	c.add(e);
2749	<	}
3009	>	for (Map.Entry e : this)
3010	>	c.add(new SnapshotEntry(e.getKey(), e.getValue()));
3011		return c.toArray(a);
3012		}
3013		}
3014
3015	+	class DescendingEntrySet extends EntrySet {
3016	+	public Iterator<Map.Entry<K,V>> iterator() {
3017	+	return new DescendingEntryIterator();
3018	+	}
3019	+	}
3020	+
3021		/**
3022		* Submaps returned by {@link ConcurrentSkipListMap} submap operations
3023		* represent a subrange of mappings of their underlying
#	Line 2769 | Line 3036 | public class ConcurrentSkipListMap<K,V>
3036		/** Underlying map */
3037		private final ConcurrentSkipListMap<K,V> m;
3038		/** lower bound key, or null if from start */
3039	<	private final K least;
3039	>	private final K least;
3040		/** upper fence key, or null if to end */
3041	<	private final K fence;
3041	>	private final K fence;
3042		// Lazily initialized view holders
3043		private transient Set<K> keySetView;
3044		private transient Set<Map.Entry<K,V>> entrySetView;
3045		private transient Collection<V> valuesView;
3046	+	private transient Set<K> descendingKeySetView;
3047	+	private transient Set<Map.Entry<K,V>> descendingEntrySetView;
3048
3049		/**
3050	<	* Creates a new submap.
3050	>	* Creates a new submap.
3051		* @param least inclusive least value, or <tt>null</tt> if from start
3052		* @param fence exclusive upper bound or <tt>null</tt> if to end
3053	<	* @throws IllegalArgumentException if least and fence nonnull
3053	>	* @throws IllegalArgumentException if least and fence non-null
3054		*  and least greater than fence
3055		*/
3056	<	ConcurrentSkipListSubMap(ConcurrentSkipListMap<K,V> map,
3056	>	ConcurrentSkipListSubMap(ConcurrentSkipListMap<K,V> map,
3057		K least, K fence) {
3058	<	if (least != null && fence != null && map.compare(least, fence) > 0)
3058	>	if (least != null &&
3059	>	fence != null &&
3060	>	map.compare(least, fence) > 0)
3061		throw new IllegalArgumentException("inconsistent range");
3062		this.m = map;
3063		this.least = least;
#	Line 2812 | Line 3083 | public class ConcurrentSkipListMap<K,V>
3083		}
3084
3085		boolean isBeforeEnd(ConcurrentSkipListMap.Node<K,V> n) {
3086	<	return (n != null &&
3087	<	(fence == null ||
3086	>	return (n != null &&
3087	>	(fence == null ||
3088		n.key == null || // pass by markers and headers
3089		m.compare(fence, n.key) > 0));
3090		}
#	Line 2847 | Line 3118 | public class ConcurrentSkipListMap<K,V>
3118		return fence;
3119		}
3120
2850	–	/**
2851	–	* Non-exception throwing version of firstKey needed by
2852	–	* ConcurrentSkipListSubSet
2853	–	* @return first key, or <tt>null</tt> if empty
2854	–	*/
2855	–	K lowestKey() {
2856	–	ConcurrentSkipListMap.Node<K,V> n = firstNode();
2857	–	if (isBeforeEnd(n))
2858	–	return n.key;
2859	–	else
2860	–	return null;
2861	–	}
2862	–
2863	–	/**
2864	–	* Non-exception throwing version of highestKey needed by
2865	–	* ConcurrentSkipListSubSet
2866	–	* @return last key, or <tt>null</tt> if empty
2867	–	*/
2868	–	K highestKey() {
2869	–	ConcurrentSkipListMap.Node<K,V> n = lastNode();
2870	–	if (isBeforeEnd(n))
2871	–	return n.key;
2872	–	else
2873	–	return null;
2874	–	}
3121
3122		/* ----------------  Map API methods -------------- */
3123
2878	–	/**
2879	–	* Returns <tt>true</tt> if this map contains a mapping for
2880	–	* the specified key.
2881	–	* @param key key whose presence in this map is to be tested.
2882	–	* @return <tt>true</tt> if this map contains a mapping for
2883	–	* the specified key.
2884	–	* @throws ClassCastException if the key cannot be compared
2885	–	* with the keys currently in the map.
2886	–	* @throws NullPointerException if the key is <tt>null</tt>.
2887	–	*/
3124		public boolean containsKey(Object key) {
3125		K k = (K)key;
3126		return inHalfOpenRange(k) && m.containsKey(k);
3127		}
3128
2893	–	/**
2894	–	* Returns the value to which this map maps the specified key.
2895	–	* Returns <tt>null</tt> if the map contains no mapping for
2896	–	* this key.
2897	–	*
2898	–	* @param key key whose associated value is to be returned.
2899	–	* @return the value to which this map maps the specified key,
2900	–	* or <tt>null</tt> if the map contains no mapping for the
2901	–	* key.
2902	–	* @throws ClassCastException if the key cannot be compared
2903	–	* with the keys currently in the map.
2904	–	* @throws NullPointerException if the key is <tt>null</tt>.
2905	–	*/
3129		public V get(Object key) {
3130		K k = (K)key;
3131		return ((!inHalfOpenRange(k)) ? null : m.get(k));
3132		}
3133
2911	–	/**
2912	–	* Associates the specified value with the specified key in
2913	–	* this map.  If the map previously contained a mapping for
2914	–	* this key, the old value is replaced.
2915	–	*
2916	–	* @param key key with which the specified value is to be associated.
2917	–	* @param value value to be associated with the specified key.
2918	–	*
2919	–	* @return previous value associated with specified key, or
2920	–	* <tt>null</tt> if there was no mapping for key.
2921	–	* @throws ClassCastException if the key cannot be compared
2922	–	* with the keys currently in the map.
2923	–	* @throws IllegalArgumentException if key outside range of
2924	–	* this submap.
2925	–	* @throws NullPointerException if the key or value are <tt>null</tt>.
2926	–	*/
3134		public V put(K key, V value) {
3135		checkKey(key);
3136		return m.put(key, value);
3137		}
3138
2932	–	/**
2933	–	* Removes the mapping for this key from this Map if present.
2934	–	*
2935	–	* @param key key for which mapping should be removed
2936	–	* @return previous value associated with specified key, or
2937	–	* <tt>null</tt> if there was no mapping for key.
2938	–	*
2939	–	* @throws ClassCastException if the key cannot be compared
2940	–	* with the keys currently in the map.
2941	–	* @throws NullPointerException if the key is <tt>null</tt>.
2942	–	*/
3139		public V remove(Object key) {
3140		K k = (K)key;
3141		return (!inHalfOpenRange(k))? null : m.remove(k);
3142		}
3143
2948	–	/**
2949	–	* Returns the number of elements in this map.  If this map
2950	–	* contains more than <tt>Integer.MAX_VALUE</tt> elements, it
2951	–	* returns <tt>Integer.MAX_VALUE</tt>.
2952	–	*
2953	–	* <p>Beware that, unlike in most collections, this method is
2954	–	* <em>NOT</em> a constant-time operation. Because of the
2955	–	* asynchronous nature of these maps, determining the current
2956	–	* number of elements requires traversing them all to count them.
2957	–	* Additionally, it is possible for the size to change during
2958	–	* execution of this method, in which case the returned result
2959	–	* will be inaccurate. Thus, this method is typically not very
2960	–	* useful in concurrent applications.
2961	–	*
2962	–	* @return  the number of elements in this map.
2963	–	*/
3144		public int size() {
3145		long count = 0;
3146	<	for (ConcurrentSkipListMap.Node<K,V> n = firstNode();
3147	<	isBeforeEnd(n);
3146	>	for (ConcurrentSkipListMap.Node<K,V> n = firstNode();
3147	>	isBeforeEnd(n);
3148		n = n.next) {
3149		if (n.getValidValue() != null)
3150		++count;
#	Line 2972 | Line 3152 | public class ConcurrentSkipListMap<K,V>
3152		return count >= Integer.MAX_VALUE? Integer.MAX_VALUE : (int)count;
3153		}
3154
2975	–	/**
2976	–	* Returns <tt>true</tt> if this map contains no key-value mappings.
2977	–	* @return <tt>true</tt> if this map contains no key-value mappings.
2978	–	*/
3155		public boolean isEmpty() {
3156		return !isBeforeEnd(firstNode());
3157		}
3158
2983	–	/**
2984	–	* Returns <tt>true</tt> if this map maps one or more keys to the
2985	–	* specified value.  This operation requires time linear in the
2986	–	* Map size.
2987	–	*
2988	–	* @param value value whose presence in this Map is to be tested.
2989	–	* @return  <tt>true</tt> if a mapping to <tt>value</tt> exists;
2990	–	*              <tt>false</tt> otherwise.
2991	–	* @throws  NullPointerException  if the value is <tt>null</tt>.
2992	–	*/
3159		public boolean containsValue(Object value) {
3160	<	if (value == null)
3160	>	if (value == null)
3161		throw new NullPointerException();
3162	<	for (ConcurrentSkipListMap.Node<K,V> n = firstNode();
3163	<	isBeforeEnd(n);
3162	>	for (ConcurrentSkipListMap.Node<K,V> n = firstNode();
3163	>	isBeforeEnd(n);
3164		n = n.next) {
3165		V v = n.getValidValue();
3166		if (v != null && value.equals(v))
#	Line 3003 | Line 3169 | public class ConcurrentSkipListMap<K,V>
3169		return false;
3170		}
3171
3006	–	/**
3007	–	* Removes all mappings from this map.
3008	–	*/
3172		public void clear() {
3173	<	for (ConcurrentSkipListMap.Node<K,V> n = firstNode();
3174	<	isBeforeEnd(n);
3173	>	for (ConcurrentSkipListMap.Node<K,V> n = firstNode();
3174	>	isBeforeEnd(n);
3175		n = n.next) {
3176		if (n.getValidValue() != null)
3177		m.remove(n.key);
#	Line 3017 | Line 3180 | public class ConcurrentSkipListMap<K,V>
3180
3181		/* ----------------  ConcurrentMap API methods -------------- */
3182
3020	–	/**
3021	–	* If the specified key is not already associated
3022	–	* with a value, associate it with the given value.
3023	–	* This is equivalent to
3024	–	* <pre>
3025	–	*   if (!map.containsKey(key))
3026	–	*      return map.put(key, value);
3027	–	*   else
3028	–	*      return map.get(key);
3029	–	* </pre>
3030	–	* Except that the action is performed atomically.
3031	–	* @param key key with which the specified value is to be associated.
3032	–	* @param value value to be associated with the specified key.
3033	–	* @return previous value associated with specified key, or
3034	–	* <tt>null</tt> if there was no mapping for key.
3035	–	*
3036	–	* @throws ClassCastException if the key cannot be compared
3037	–	* with the keys currently in the map.
3038	–	* @throws IllegalArgumentException if key outside range of
3039	–	* this submap.
3040	–	* @throws NullPointerException if the key or value are <tt>null</tt>.
3041	–	*/
3183		public V putIfAbsent(K key, V value) {
3184		checkKey(key);
3185		return m.putIfAbsent(key, value);
3186		}
3187
3047	–	/**
3048	–	* Remove entry for key only if currently mapped to given value.
3049	–	* Acts as
3050	–	* <pre>
3051	–	*  if ((map.containsKey(key) && map.get(key).equals(value)) {
3052	–	*     map.remove(key);
3053	–	*     return true;
3054	–	* } else return false;
3055	–	* </pre>
3056	–	* except that the action is performed atomically.
3057	–	* @param key key with which the specified value is associated.
3058	–	* @param value value associated with the specified key.
3059	–	* @return true if the value was removed, false otherwise
3060	–	* @throws ClassCastException if the key cannot be compared
3061	–	* with the keys currently in the map.
3062	–	* @throws NullPointerException if the key or value are
3063	–	* <tt>null</tt>.
3064	–	*/
3188		public boolean remove(Object key, Object value) {
3189		K k = (K)key;
3190		return inHalfOpenRange(k) && m.remove(k, value);
3191		}
3192
3070	–	/**
3071	–	* Replace entry for key only if currently mapped to given value.
3072	–	* Acts as
3073	–	* <pre>
3074	–	*  if ((map.containsKey(key) && map.get(key).equals(oldValue)) {
3075	–	*     map.put(key, newValue);
3076	–	*     return true;
3077	–	* } else return false;
3078	–	* </pre>
3079	–	* except that the action is performed atomically.
3080	–	* @param key key with which the specified value is associated.
3081	–	* @param oldValue value expected to be associated with the specified key.
3082	–	* @param newValue value to be associated with the specified key.
3083	–	* @return true if the value was replaced
3084	–	* @throws ClassCastException if the key cannot be compared
3085	–	* with the keys currently in the map.
3086	–	* @throws IllegalArgumentException if key outside range of
3087	–	* this submap.
3088	–	* @throws NullPointerException if key, oldValue or newValue
3089	–	* are <tt>null</tt>.
3090	–	*/
3193		public boolean replace(K key, V oldValue, V newValue) {
3194		checkKey(key);
3195		return m.replace(key, oldValue, newValue);
3196		}
3197
3096	–	/**
3097	–	* Replace entry for key only if currently mapped to some value.
3098	–	* Acts as
3099	–	* <pre>
3100	–	*  if ((map.containsKey(key)) {
3101	–	*     return map.put(key, value);
3102	–	* } else return null;
3103	–	* </pre>
3104	–	* except that the action is performed atomically.
3105	–	* @param key key with which the specified value is associated.
3106	–	* @param value value to be associated with the specified key.
3107	–	* @return previous value associated with specified key, or
3108	–	* <tt>null</tt> if there was no mapping for key.
3109	–	* @throws ClassCastException if the key cannot be compared
3110	–	* with the keys currently in the map.
3111	–	* @throws IllegalArgumentException if key outside range of
3112	–	* this submap.
3113	–	* @throws NullPointerException if the key or value are
3114	–	* <tt>null</tt>.
3115	–	*/
3198		public V replace(K key, V value) {
3199		checkKey(key);
3200		return m.replace(key, value);
#	Line 3120 | Line 3202 | public class ConcurrentSkipListMap<K,V>
3202
3203		/* ----------------  SortedMap API methods -------------- */
3204
3123	–	/**
3124	–	* Returns the comparator used to order this map, or <tt>null</tt>
3125	–	* if this map uses its keys' natural order.
3126	–	*
3127	–	* @return the comparator associated with this map, or
3128	–	* <tt>null</tt> if it uses its keys' natural sort method.
3129	–	*/
3205		public Comparator<? super K> comparator() {
3206		return m.comparator();
3207		}
3208
3134	–	/**
3135	–	* Returns the first (lowest) key currently in this map.
3136	–	*
3137	–	* @return the first (lowest) key currently in this map.
3138	–	* @throws    NoSuchElementException Map is empty.
3139	–	*/
3209		public K firstKey() {
3210		ConcurrentSkipListMap.Node<K,V> n = firstNode();
3211		if (isBeforeEnd(n))
#	Line 3145 | Line 3214 | public class ConcurrentSkipListMap<K,V>
3214		throw new NoSuchElementException();
3215		}
3216
3148	–	/**
3149	–	* Returns the last (highest) key currently in this map.
3150	–	*
3151	–	* @return the last (highest) key currently in this map.
3152	–	* @throws    NoSuchElementException Map is empty.
3153	–	*/
3217		public K lastKey() {
3218		ConcurrentSkipListMap.Node<K,V> n = lastNode();
3219		if (n != null) {
#	Line 3161 | Line 3224 | public class ConcurrentSkipListMap<K,V>
3224		throw new NoSuchElementException();
3225		}
3226
3164	–	/**
3165	–	* Returns a view of the portion of this map whose keys range
3166	–	* from <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>,
3167	–	* exclusive.  (If <tt>fromKey</tt> and <tt>toKey</tt> are
3168	–	* equal, the returned sorted map is empty.)  The returned
3169	–	* sorted map is backed by this map, so changes in the
3170	–	* returned sorted map are reflected in this map, and
3171	–	* vice-versa.
3172	–
3173	–	* @param fromKey low endpoint (inclusive) of the subMap.
3174	–	* @param toKey high endpoint (exclusive) of the subMap.
3175	–	*
3176	–	* @return a view of the portion of this map whose keys range
3177	–	* from <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>,
3178	–	* exclusive.
3179	–	*
3180	–	* @throws ClassCastException if <tt>fromKey</tt> and
3181	–	* <tt>toKey</tt> cannot be compared to one another using this
3182	–	* map's comparator (or, if the map has no comparator, using
3183	–	* natural ordering).
3184	–	* @throws IllegalArgumentException if <tt>fromKey</tt> is
3185	–	* greater than <tt>toKey</tt> or either key is outside of
3186	–	* the range of this submap.
3187	–	* @throws NullPointerException if <tt>fromKey</tt> or
3188	–	* <tt>toKey</tt> is <tt>null</tt>.
3189	–	*/
3227		public ConcurrentNavigableMap<K,V> subMap(K fromKey, K toKey) {
3228		if (fromKey == null || toKey == null)
3229		throw new NullPointerException();
#	Line 3195 | Line 3232 | public class ConcurrentSkipListMap<K,V>
3232		return new ConcurrentSkipListSubMap(m, fromKey, toKey);
3233		}
3234
3198	–	/**
3199	–	* Returns a view of the portion of this map whose keys are
3200	–	* strictly less than <tt>toKey</tt>.  The returned sorted map
3201	–	* is backed by this map, so changes in the returned sorted
3202	–	* map are reflected in this map, and vice-versa.
3203	–	* @param toKey high endpoint (exclusive) of the headMap.
3204	–	* @return a view of the portion of this map whose keys are
3205	–	* strictly less than <tt>toKey</tt>.
3206	–	*
3207	–	* @throws ClassCastException if <tt>toKey</tt> is not
3208	–	* compatible with this map's comparator (or, if the map has
3209	–	* no comparator, if <tt>toKey</tt> does not implement
3210	–	* <tt>Comparable</tt>).
3211	–	* @throws IllegalArgumentException if <tt>toKey</tt> is
3212	–	* outside of the range of this submap.
3213	–	* @throws NullPointerException if <tt>toKey</tt> is
3214	–	* <tt>null</tt>.
3215	–	*/
3235		public ConcurrentNavigableMap<K,V> headMap(K toKey) {
3236		if (toKey == null)
3237		throw new NullPointerException();
#	Line 3221 | Line 3240 | public class ConcurrentSkipListMap<K,V>
3240		return new ConcurrentSkipListSubMap(m, least, toKey);
3241		}
3242
3224	–	/**
3225	–	* Returns a view of the portion of this map whose keys are
3226	–	* greater than or equal to <tt>fromKey</tt>.  The returned sorted
3227	–	* map is backed by this map, so changes in the returned sorted
3228	–	* map are reflected in this map, and vice-versa.
3229	–	* @param fromKey low endpoint (inclusive) of the tailMap.
3230	–	* @return a view of the portion of this map whose keys are
3231	–	* greater than or equal to <tt>fromKey</tt>.
3232	–	* @throws ClassCastException if <tt>fromKey</tt> is not
3233	–	* compatible with this map's comparator (or, if the map has
3234	–	* no comparator, if <tt>fromKey</tt> does not implement
3235	–	* <tt>Comparable</tt>).
3236	–	* @throws IllegalArgumentException if <tt>fromKey</tt> is
3237	–	* outside of the range of this submap.
3238	–	* @throws NullPointerException if <tt>fromKey</tt> is
3239	–	* <tt>null</tt>.
3240	–	*/
3243		public  ConcurrentNavigableMap<K,V> tailMap(K fromKey) {
3244		if (fromKey == null)
3245		throw new NullPointerException();
#	Line 3248 | Line 3250 | public class ConcurrentSkipListMap<K,V>
3250
3251		/* ----------------  Relational methods -------------- */
3252
3251	–	/**
3252	–	* Returns a key-value mapping associated with the least key
3253	–	* greater than or equal to the given key, or <tt>null</tt> if there is
3254	–	* no such entry. The returned entry does <em>not</em> support
3255	–	* the <tt>Entry.setValue</tt> method.
3256	–	*
3257	–	* @param key the key.
3258	–	* @return an Entry associated with ceiling of given key, or <tt>null</tt>
3259	–	* if there is no such Entry.
3260	–	* @throws ClassCastException if key cannot be compared with the keys
3261	–	*            currently in the map.
3262	–	* @throws NullPointerException if key is <tt>null</tt>.
3263	–	*/
3253		public Map.Entry<K,V> ceilingEntry(K key) {
3254	<	return m.getCeiling(key, least, fence);
3254	>	return (SnapshotEntry<K,V>)
3255	>	m.getNear(key, m.GT|m.EQ, least, fence, false);
3256	>	}
3257	>
3258	>	public K ceilingKey(K key) {
3259	>	return (K)
3260	>	m.getNear(key, m.GT|m.EQ, least, fence, true);
3261		}
3262
3268	–	/**
3269	–	* Returns a key-value mapping associated with the greatest
3270	–	* key strictly less than the given key, or <tt>null</tt> if there is no
3271	–	* such entry. The returned entry does <em>not</em> support
3272	–	* the <tt>Entry.setValue</tt> method.
3273	–	*
3274	–	* @param key the key.
3275	–	* @return an Entry with greatest key less than the given
3276	–	* key, or <tt>null</tt> if there is no such Entry.
3277	–	* @throws ClassCastException if key cannot be compared with the keys
3278	–	*            currently in the map.
3279	–	* @throws NullPointerException if key is <tt>null</tt>.
3280	–	*/
3263		public Map.Entry<K,V> lowerEntry(K key) {
3264	<	return m.getLower(key, least, fence);
3264	>	return (SnapshotEntry<K,V>)
3265	>	m.getNear(key, m.LT, least, fence, false);
3266	>	}
3267	>
3268	>	public K lowerKey(K key) {
3269	>	return (K)
3270	>	m.getNear(key, m.LT, least, fence, true);
3271		}
3272
3285	–	/**
3286	–	* Returns a key-value mapping associated with the greatest
3287	–	* key less than or equal to the given key, or <tt>null</tt> if there is no
3288	–	* such entry. The returned entry does <em>not</em> support
3289	–	* the <tt>Entry.setValue</tt> method.
3290	–	*
3291	–	* @param key the key.
3292	–	* @return an Entry associated with floor of given key, or <tt>null</tt>
3293	–	* if there is no such Entry.
3294	–	* @throws ClassCastException if key cannot be compared with the keys
3295	–	*            currently in the map.
3296	–	* @throws NullPointerException if key is <tt>null</tt>.
3297	–	*/
3273		public Map.Entry<K,V> floorEntry(K key) {
3274	<	return m.getFloor(key, least, fence);
3274	>	return (SnapshotEntry<K,V>)
3275	>	m.getNear(key, m.LT|m.EQ, least, fence, false);
3276		}
3277	<
3278	<	/**
3279	<	* Returns a key-value mapping associated with the least
3280	<	* key strictly greater than the given key, or <tt>null</tt> if there is no
3281	<	* such entry. The returned entry does <em>not</em> support
3282	<	* the <tt>Entry.setValue</tt> method.
3283	<	*
3308	<	* @param key the key.
3309	<	* @return an Entry with least key greater than the given key, or
3310	<	* <tt>null</tt> if there is no such Entry.
3311	<	* @throws ClassCastException if key cannot be compared with the keys
3312	<	*            currently in the map.
3313	<	* @throws NullPointerException if key is <tt>null</tt>.
3314	<	*/
3277	>
3278	>	public K floorKey(K key) {
3279	>	return (K)
3280	>	m.getNear(key, m.LT|m.EQ, least, fence, true);
3281	>	}
3282	>
3283	>
3284		public Map.Entry<K,V> higherEntry(K key) {
3285	<	return m.getHigher(key, least, fence);
3285	>	return (SnapshotEntry<K,V>)
3286	>	m.getNear(key, m.GT, least, fence, false);
3287	>	}
3288	>
3289	>	public K higherKey(K key) {
3290	>	return (K)
3291	>	m.getNear(key, m.GT, least, fence, true);
3292		}
3293
3319	–	/**
3320	–	* Returns a key-value mapping associated with the least
3321	–	* key in this map, or <tt>null</tt> if the map is empty.
3322	–	* The returned entry does <em>not</em> support
3323	–	* the <tt>Entry.setValue</tt> method.
3324	–	*
3325	–	* @return an Entry with least key, or <tt>null</tt>
3326	–	* if the map is empty.
3327	–	*/
3294		public Map.Entry<K,V> firstEntry() {
3295		for (;;) {
3296		ConcurrentSkipListMap.Node<K,V> n = firstNode();
3297	<	if (!isBeforeEnd(n))
3297	>	if (!isBeforeEnd(n))
3298		return null;
3299		Map.Entry<K,V> e = n.createSnapshot();
3300		if (e != null)
#	Line 3336 | Line 3302 | public class ConcurrentSkipListMap<K,V>
3302		}
3303		}
3304
3339	–	/**
3340	–	* Returns a key-value mapping associated with the greatest
3341	–	* key in this map, or <tt>null</tt> if the map is empty.
3342	–	* The returned entry does <em>not</em> support
3343	–	* the <tt>Entry.setValue</tt> method.
3344	–	*
3345	–	* @return an Entry with greatest key, or <tt>null</tt>
3346	–	* if the map is empty.
3347	–	*/
3305		public Map.Entry<K,V> lastEntry() {
3306		for (;;) {
3307		ConcurrentSkipListMap.Node<K,V> n = lastNode();
#	Line 3356 | Line 3313 | public class ConcurrentSkipListMap<K,V>
3313		}
3314		}
3315
3359	–	/**
3360	–	* Removes and returns a key-value mapping associated with
3361	–	* the least key in this map, or <tt>null</tt> if the map is empty.
3362	–	* The returned entry does <em>not</em> support
3363	–	* the <tt>Entry.setValue</tt> method.
3364	–	*
3365	–	* @return the removed first entry of this map, or <tt>null</tt>
3366	–	* if the map is empty.
3367	–	*/
3316		public Map.Entry<K,V> pollFirstEntry() {
3317	<	return m.removeFirstEntryOfSubrange(least, fence);
3317	>	return (SnapshotEntry<K,V>)
3318	>	m.removeFirstEntryOfSubrange(least, fence, false);
3319		}
3320
3372	–	/**
3373	–	* Removes and returns a key-value mapping associated with
3374	–	* the greatest key in this map, or <tt>null</tt> if the map is empty.
3375	–	* The returned entry does <em>not</em> support
3376	–	* the <tt>Entry.setValue</tt> method.
3377	–	*
3378	–	* @return the removed last entry of this map, or <tt>null</tt>
3379	–	* if the map is empty.
3380	–	*/
3321		public Map.Entry<K,V> pollLastEntry() {
3322	<	return m.removeLastEntryOfSubrange(least, fence);
3322	>	return (SnapshotEntry<K,V>)
3323	>	m.removeLastEntryOfSubrange(least, fence, false);
3324		}
3325
3326		/* ---------------- Submap Views -------------- */
3327
3387	–	/**
3388	–	* Returns a set view of the keys contained in this map.  The
3389	–	* set is backed by the map, so changes to the map are
3390	–	* reflected in the set, and vice-versa.  The set supports
3391	–	* element removal, which removes the corresponding mapping
3392	–	* from this map, via the <tt>Iterator.remove</tt>,
3393	–	* <tt>Set.remove</tt>, <tt>removeAll</tt>,
3394	–	* <tt>retainAll</tt>, and <tt>clear</tt> operations.  It does
3395	–	* not support the <tt>add</tt> or <tt>addAll</tt> operations.
3396	–	* The view's <tt>iterator</tt> is a "weakly consistent"
3397	–	* iterator that will never throw {@link
3398	–	* java.util.ConcurrentModificationException}, and guarantees
3399	–	* to traverse elements as they existed upon construction of
3400	–	* the iterator, and may (but is not guaranteed to) reflect
3401	–	* any modifications subsequent to construction.
3402	–	*
3403	–	* @return a set view of the keys contained in this map.
3404	–	*/
3328		public Set<K> keySet() {
3329		Set<K> ks = keySetView;
3330		return (ks != null) ? ks : (keySetView = new KeySetView());
#	Line 3434 | Line 3357 | public class ConcurrentSkipListMap<K,V>
3357		}
3358		}
3359
3360	<	/**
3361	<	* Returns a collection view of the values contained in this
3362	<	* map.  The collection is backed by the map, so changes to
3363	<	* the map are reflected in the collection, and vice-versa.
3364	<	* The collection supports element removal, which removes the
3365	<	* corresponding mapping from this map, via the
3366	<	* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
3367	<	* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
3368	<	* operations.  It does not support the <tt>add</tt> or
3369	<	* <tt>addAll</tt> operations.  The view's <tt>iterator</tt>
3370	<	* is a "weakly consistent" iterator that will never throw
3448	<	* {@link java.util.ConcurrentModificationException}, and
3449	<	* guarantees to traverse elements as they existed upon
3450	<	* construction of the iterator, and may (but is not
3451	<	* guaranteed to) reflect any modifications subsequent to
3452	<	* construction.
3453	<	*
3454	<	* @return a collection view of the values contained in this map.
3455	<	*/
3360	>	public Set<K> descendingKeySet() {
3361	>	Set<K> ks = descendingKeySetView;
3362	>	return (ks != null) ? ks : (descendingKeySetView = new DescendingKeySetView());
3363	>	}
3364	>
3365	>	class DescendingKeySetView extends KeySetView {
3366	>	public Iterator<K> iterator() {
3367	>	return m.descendingSubMapKeyIterator(least, fence);
3368	>	}
3369	>	}
3370	>
3371		public Collection<V> values() {
3372		Collection<V> vs = valuesView;
3373		return (vs != null) ? vs : (valuesView = new ValuesView());
#	Line 3485 | Line 3400 | public class ConcurrentSkipListMap<K,V>
3400		}
3401		}
3402
3488	–	/**
3489	–	* Returns a collection view of the mappings contained in this
3490	–	* map.  Each element in the returned collection is a
3491	–	* <tt>Map.Entry</tt>.  The collection is backed by the map,
3492	–	* so changes to the map are reflected in the collection, and
3493	–	* vice-versa.  The collection supports element removal, which
3494	–	* removes the corresponding mapping from the map, via the
3495	–	* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
3496	–	* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
3497	–	* operations.  It does not support the <tt>add</tt> or
3498	–	* <tt>addAll</tt> operations.  The view's <tt>iterator</tt>
3499	–	* is a "weakly consistent" iterator that will never throw
3500	–	* {@link java.util.ConcurrentModificationException}, and
3501	–	* guarantees to traverse elements as they existed upon
3502	–	* construction of the iterator, and may (but is not
3503	–	* guaranteed to) reflect any modifications subsequent to
3504	–	* construction. The <tt>Map.Entry</tt> elements returned by
3505	–	* <tt>iterator.next()</tt> do <em>not</em> support the
3506	–	* <tt>setValue</tt> operation.
3507	–	*
3508	–	* @return a collection view of the mappings contained in this map.
3509	–	*/
3403		public Set<Map.Entry<K,V>> entrySet() {
3404		Set<Map.Entry<K,V>> es = entrySetView;
3405		return (es != null) ? es : (entrySetView = new EntrySetView());
#	Line 3543 | Line 3436 | public class ConcurrentSkipListMap<K,V>
3436		}
3437		public Object[] toArray() {
3438		Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>();
3439	<	for (ConcurrentSkipListMap.Node<K,V> n = firstNode();
3440	<	isBeforeEnd(n);
3548	<	n = n.next) {
3549	<	Map.Entry<K,V> e = n.createSnapshot();
3550	<	if (e != null)
3551	<	c.add(e);
3552	<	}
3439	>	for (Map.Entry e : this)
3440	>	c.add(new SnapshotEntry(e.getKey(), e.getValue()));
3441		return c.toArray();
3442		}
3443		public <T> T[] toArray(T[] a) {
3444		Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>();
3445	<	for (ConcurrentSkipListMap.Node<K,V> n = firstNode();
3446	<	isBeforeEnd(n);
3559	<	n = n.next) {
3560	<	Map.Entry<K,V> e = n.createSnapshot();
3561	<	if (e != null)
3562	<	c.add(e);
3563	<	}
3445	>	for (Map.Entry e : this)
3446	>	c.add(new SnapshotEntry(e.getKey(), e.getValue()));
3447		return c.toArray(a);
3448		}
3449		}
3567	–	}
3450
3451	+	public Set<Map.Entry<K,V>> descendingEntrySet() {
3452	+	Set<Map.Entry<K,V>> es = descendingEntrySetView;
3453	+	return (es != null) ? es : (descendingEntrySetView = new DescendingEntrySetView());
3454	+	}
3455	+
3456	+	class DescendingEntrySetView extends EntrySetView {
3457	+	public Iterator<Map.Entry<K,V>> iterator() {
3458	+	return m.descendingSubMapEntryIterator(least, fence);
3459	+	}
3460	+	}
3461	+	}
3462		}

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