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Comparing jsr166/src/jsr166x/ConcurrentSkipListMap.java (file contents):
Revision 1.1 by dl, Wed Aug 11 10:58:15 2004 UTC vs.
Revision 1.28 by jsr166, Tue Feb 5 19:54:07 2013 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7	<	package jsr166x;
7	>	package jsr166x;
8
9		import java.util.*;
10		import java.util.concurrent.*;
11		import java.util.concurrent.atomic.*;
12
13		/**
14	<	* A scalable {@link SortedMap} and {@link ConcurrentMap}
15	<	* implementation.  This class maintains a map in ascending key order,
16	<	* sorted according to the <i>natural order</i> for the key's class
17	<	* (see {@link Comparable}), or by the {@link Comparator} provided at
18	<	* creation time, depending on which constructor is used.
14	>	* A scalable {@link ConcurrentNavigableMap} implementation.  This
15	>	* class maintains a map in ascending key order, sorted according to
16	>	* the <i>natural order</i> for the key's class (see {@link
17	>	* Comparable}), or by the {@link Comparator} provided at creation
18	>	* time, depending on which constructor is used.
19		*
20		* <p>This class implements a concurrent variant of <a
21		* href="http://www.cs.umd.edu/~pugh/">SkipLists</a> providing
22		* expected average <i>log(n)</i> time cost for the
23	<	* <tt>containsKey</tt>, <tt>get</tt>, <tt>put</tt> and
24	<	* <tt>remove</tt> operations and their variants.  Insertion, removal,
23	>	* {@code containsKey}, {@code get}, {@code put} and
24	>	* {@code remove} operations and their variants.  Insertion, removal,
25		* update, and access operations safely execute concurrently by
26		* multiple threads. Iterators are <i>weakly consistent</i>, returning
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>This class provides extended <tt>SortedMap</tt> methods
33	<	* returning <tt>Map.Entry</tt> key-value pairs that may be useful in
34	<	* searching for closest matches. Methods <tt>lowerEntry</tt>,
35	<	* <tt>floorEntry</tt>, <tt>ceilingEntry</tt>, and
36	<	* <tt>higherEntry</tt> return entries associated with keys
37	<	* respectively less, less than or equal, greater than or equal, and
38	<	* greater than a given key, returning null if there is no such key.
39	<	* These methods are designed for locating, not traversing entries. To
40	<	* traverse, use view iterators and/or <tt>submap</tt>. The class
41	<	* additionally supports method <tt>removeFirstEntry</tt> that
42	<	* atomically returns and removes the first mapping (i.e., with least
43	<	* key), if one exists.
44	<	*
45	<	* <p> All <tt>Map.Entry</tt> pairs returned by methods in this class
33	>	* <p>All {@code Map.Entry} 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>
35	>	* produced. They do <em>not</em> support the {@code Entry.setValue}
36		* method. (Note however that it is possible to change mappings in the
37	<	* associated map using <tt>put</tt>, <tt>putIfAbsent</tt>, or
38	<	* <tt>replace</tt>, depending on exactly which effect you need.)
37	>	* associated map using {@code put}, {@code putIfAbsent}, or
38	>	* {@code replace}, depending on exactly which effect you need.)
39		*
40	<	* <p>The {@link ConcurrentSkipListSubMap} objects returned by methods
53	<	* <tt>submap</tt>, <tt>headMap</tt>, and <tt>tailMap</tt> support the
54	<	* same extended set of operations as this class, but operate on their
55	<	* designated subrange of mappings.
56	<	*
57	<	* <p>Beware that, unlike in most collections, the <tt>size</tt>
40	>	* <p>Beware that, unlike in most collections, the {@code size}
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 {@code putAll}, {@code equals}, and
45	>	* {@code clear} are <em>not</em> guaranteed to be performed
46	>	* atomically. For example, an iterator operating concurrently with a
47	>	* {@code putAll} 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}
52		* interfaces. Like most other concurrent collections, this class does
53	<	* not permit the use of <tt>null</tt> keys or values because some
53	>	* not permit the use of {@code null} keys or values because some
54		* null return values cannot be reliably distinguished from the
55		* absence of elements.
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>
62	<	implements ConcurrentMap<K,V>,
63	<	SortedMap<K,V>,
76	<	Cloneable,
61	>	public class ConcurrentSkipListMap<K,V> extends AbstractMap<K,V>
62	>	implements ConcurrentNavigableMap<K,V>,
63	>	Cloneable,
64		java.io.Serializable {
65		/*
66		* This class implements a tree-like two-dimensionally linked skip
#	Line 87 | 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 136 | Line 124 | public class ConcurrentSkipListMap<K,V>
124		* space by defining marker nodes not to have key/value fields, it
125		* isn't worth the extra type-testing overhead.  The deletion
126		* markers are rarely encountered during traversal and are
127	<	* normally quickly garbage collected.
127	>	* normally quickly garbage collected. (Note that this technique
128	>	* would not work well in systems without garbage collection.)
129		*
130		* In addition to using deletion markers, the lists also use
131		* nullness of value fields to indicate deletion, in a style
#	Line 156 | 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 172 | 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 199 | 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 276 | Line 265 | public class ConcurrentSkipListMap<K,V>
265		*
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/) and Keir Fraser's thesis
269	<	* (http://www.cl.cam.ac.uk/users/kaf24/).
268	>	* (http://www.cs.yorku.ca/~mikhail/), Keir Fraser's thesis
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 302 | 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 329 | 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,
328	>	* Initializes or resets state. Needed by constructors, clone,
329		* clear, readObject. and ConcurrentSkipListSet.clone.
330		* (Note that comparator must be separately initialized.)
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 394 | 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
406	–
402		/**
403		* compareAndSet value field
404		*/
#	Line 419 | Line 414 | public class ConcurrentSkipListMap<K,V>
414		}
415
416		/**
417	<	* Return true if this node is a marker. This method isn't
417	>	* Returns true if this node is a marker. This method isn't
418		* actually called in an any current code checking for markers
419		* because callers will have already read value field and need
420		* to use that read (not another done here) and so directly
421		* test if value points to node.
422	<	* @param n a possibly null reference to a node
422	>	*
423		* @return true if this node is a marker node
424		*/
425		boolean isMarker() {
#	Line 432 | Line 427 | public class ConcurrentSkipListMap<K,V>
427		}
428
429		/**
430	<	* Return true if this node is the header of base-level list.
430	>	* Returns true if this node is the header of base-level list.
431		* @return true if this node is header node
432		*/
433		boolean isBaseHeader() {
#	Line 470 | Line 465 | public class ConcurrentSkipListMap<K,V>
465		}
466
467		/**
468	<	* Return value if this node contains a valid key-value pair,
469	<	* else null.
468	>	* Returns value if this node contains a valid key-value pair,
469	>	* else null.
470		* @return this node's value if it isn't a marker or header or
471	<	* is deleted, else null.
471	>	* is deleted, else null
472		*/
473		V getValidValue() {
474		Object v = value;
#	Line 483 | Line 478 | public class ConcurrentSkipListMap<K,V>
478		}
479
480		/**
481	<	* Create and return a new SnapshotEntry holding current
482	<	* mapping if this node holds a valid value, else null
481	>	* Creates and returns a new SnapshotEntry holding current
482	>	* mapping if this node holds a valid value, else null.
483		* @return new entry or null
484		*/
485		SnapshotEntry<K,V> createSnapshot() {
#	Line 512 | Line 507 | public class ConcurrentSkipListMap<K,V>
507		volatile Index<K,V> right;
508
509		/**
510	<	* Creates index node with unknown right pointer
511	<	*/
517	<	Index(Node<K,V> node, Index<K,V> down) {
518	<	this.node = node;
519	<	this.key = node.key;
520	<	this.down = down;
521	<	}
522	<
523	<	/**
524	<	* Creates index node with known right pointer
525	<	*/
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 531 | 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 560 | 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 583 | 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,
587	<	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
580		/**
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	<	*/
583	>	* support the {@code Map.Entry.setValue} method.
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 607 | 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 {@code UnsupportedOperationException}.
619	>	* @throws UnsupportedOperationException always
620		*/
621		public V setValue(V value) {
622		throw new UnsupportedOperationException();
#	Line 659 | Line 644 | public class ConcurrentSkipListMap<K,V>
644
645		/**
646		* Returns a String consisting of the key followed by an
647	<	* equals sign (<tt>"="</tt>) followed by the associated
647	>	* equals sign ({@code "="}) followed by the associated
648		* value.
649	<	* @return a String representation of this entry.
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 703 | 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
698		/**
699	<	* Compare using comparator or natural ordering. Used when the
699	>	* Compares using comparator or natural ordering. Used when the
700		* ComparableUsingComparator approach doesn't apply.
701		*/
702		int compare(K k1, K k2) throws ClassCastException {
#	Line 723 | Line 708 | public class ConcurrentSkipListMap<K,V>
708		}
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.
711	>	* Returns true if given key greater than or equal to least and
712	>	* strictly less than fence, bypassing either test if least or
713	>	* fence are 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));
720		}
721
722		/**
723	<	* Return true if given key greater than or equal to least and less
723	>	* Returns true if given key greater than or equal to least and less
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 747 | Line 733 | public class ConcurrentSkipListMap<K,V>
733		/* ---------------- Traversal -------------- */
734
735		/**
736	<	* Return a base-level node with key strictly less than given key,
736	>	* Returns a base-level node with key strictly less than given key,
737		* or the base-level header if there is no such node.  Also
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 771 | 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 780 | Line 766 | public class ConcurrentSkipListMap<K,V>
766		}
767
768		/**
769	<	* Return node holding key or null if no such, clearing out any
769	>	* Returns node holding key or null if no such, clearing out any
770		* deleted nodes seen along the way.  Repeatedly traverses at
771		* base-level looking for key starting at predecessor returned
772		* from findPredecessor, processing base-level deletions as
#	Line 801 | 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 814 | 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.
810	>	* @return node holding key, or null if no such
811		*/
812		private Node<K,V> findNode(Comparable<K> key) {
813		for (;;) {
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 843 | 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 851 | 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 870 | 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 879 | Line 865 | public class ConcurrentSkipListMap<K,V>
865		}
866		if (c == 0) {
867		Object v = r.node.value;
868	<	return (v != null)? (V)v : getUsingFindNode(key);
868	>	return (v != null) ? (V)v : getUsingFindNode(key);
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 892 | Line 878 | public class ConcurrentSkipListMap<K,V>
878		int c = key.compareTo(nk);
879		if (c == 0) {
880		Object v = n.value;
881	<	return (v != null)? (V)v : getUsingFindNode(key);
881	>	return (v != null) ? (V)v : getUsingFindNode(key);
882		}
883		if (c < 0)
884		return null;
#	Line 904 | Line 890 | public class ConcurrentSkipListMap<K,V>
890		}
891
892		/**
893	<	* Perform map.get via findNode.  Used as a backup if doGet
893	>	* Performs map.get via findNode.  Used as a backup if doGet
894		* encounters an in-progress deletion.
895		* @param key the key
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 927 | 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 941 | 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 963 | 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 976 | Line 965 | public class ConcurrentSkipListMap<K,V>
965		}
966
967		/**
968	<	* Return a random level for inserting a new node.
968	>	* Returns a random level for inserting a new node.
969		* Hardwired to k=1, p=0.5, max 31.
970		*
971		* This uses a cheap pseudo-random function that according to
#	Line 990 | 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;
987		}
988
989		/**
990	<	* Create and add index nodes for given node.
990	>	* Creates and adds index nodes for given node.
991		* @param z the node
992		* @param level the level of the index
993		*/
#	Line 1009 | 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 1024 | 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 1038 | 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 1050 | Line 1039 | public class ConcurrentSkipListMap<K,V>
1039		}
1040
1041		/**
1042	<	* Add given index nodes from given level down to 1.
1042	>	* Adds given index nodes from given level down to 1.
1043		* @param idx the topmost index node being inserted
1044		* @param h the value of head to use to insert. This must be
1045	<	* snapshotted by callers to provide correct insertion level
1045	>	* snapshotted by callers to provide correct insertion level.
1046		* @param indexLevel the level of the index
1047		*/
1048		private void addIndex(Index<K,V> idx, HeadIndex<K,V> h, int indexLevel) {
#	Line 1076 | 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 1090 | 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 1115 | 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 1131 | 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 1155 | 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 1175 | 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 1196 | 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 (;;) {
1218	–	// 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
1226	<	*/
1227	<	K removeFirstKey() {
1234	<	for (;;) {
1235	<	Node<K,V> b = head.node;
1236	<	Node<K,V> n = b.next;
1237	<	if (n == null)
1238	<	return null;
1239	<	Node<K,V> f = n.next;
1240	<	if (n != b.next)
1241	<	continue;
1242	<	Object v = n.value;
1243	<	if (v == null) {
1244	<	n.helpDelete(b, f);
1245	<	continue;
1246	<	}
1247	<	if (!n.casValue(v, null))
1248	<	continue;
1249	<	if (!n.appendMarker(f) || !b.casNext(n, f))
1250	<	findFirst(); // retry
1251	<	clearIndexToFirst();
1252	<	return n.key;
1253	<	}
1254	<	}
1255	<
1256	<	/**
1257	<	* Remove first entry; return SnapshotEntry or null if empty.
1224	>	* Removes 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	<	private SnapshotEntry<K,V> doRemoveFirstEntry() {
1230	<	/*
1261	<	* This must be mostly duplicated from removeFirstKey because we
1262	<	* need to save the last value read before it is nulled out
1263	<	*/
1264	<	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 1279 | 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
1254	>	* Clears out index nodes associated with deleted first entry.
1255	>	* Needed by doRemoveFirst.
1256		*/
1257		private void clearIndexToFirst() {
1258		for (;;) {
#	Line 1293 | 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 1303 | Line 1270 | public class ConcurrentSkipListMap<K,V>
1270		}
1271		}
1272
1273	+	/**
1274	+	* Removes 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 1320 | 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 1329 | 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)
1309	<	return (b.isBaseHeader())? null : b;
1308	>	if (n == null)
1309	>	return b.isBaseHeader() ? null : b;
1310		Node<K,V> f = n.next;            // inconsistent read
1311		if (n != b.next)
1312		break;
#	Line 1349 | Line 1325 | public class ConcurrentSkipListMap<K,V>
1325		}
1326		}
1327
1328	+
1329	+	/**
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	+	Object doRemoveLast(boolean keyOnly) {
1335	+	for (;;) {
1336	+	Node<K,V> b = findPredecessorOfLast();
1337	+	Node<K,V> n = b.next;
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;
1348	+	Object v = n.value;
1349	+	if (v == null) {                    // n is deleted
1350	+	n.helpDelete(b, f);
1351	+	break;
1352	+	}
1353	+	if (v == n || b.value == null)      // b is deleted
1354	+	break;
1355	+	if (f != null) {
1356	+	b = n;
1357	+	n = f;
1358	+	continue;
1359	+	}
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(ck);           // Clean index
1368	+	if (head.right == null)
1369	+	tryReduceLevel();
1370	+	}
1371	+	return keyOnly ? key : new SnapshotEntry<K,V>(key, (V)v);
1372	+	}
1373	+	}
1374	+	}
1375	+
1376	+	/**
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 Node<K,V> findPredecessorOfLast() {
1384	+	for (;;) {
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	+
1407	+	/**
1408	+	* Removes last entry; return key or null if empty.
1409	+	*/
1410	+	K pollLastKey() {
1411	+	return (K)doRemoveLast(true);
1412	+	}
1413	+
1414		/* ---------------- Relational operations -------------- */
1415
1416		// Control values OR'ed as arguments to findNear
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 1369 | 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)
1435	<	return ((rel & LT) == 0 || b.isBaseHeader())? null : b;
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
1438		break;
#	Line 1386 | Line 1448 | public class ConcurrentSkipListMap<K,V>
1448		(c <  0 && (rel & LT) == 0))
1449		return n;
1450		if ( c <= 0 && (rel & LT) != 0)
1451	<	return (b.isBaseHeader())? null : b;
1451	>	return b.isBaseHeader() ? null : b;
1452		b = n;
1453		n = f;
1454		}
#	Line 1394 | Line 1456 | public class ConcurrentSkipListMap<K,V>
1456		}
1457
1458		/**
1459	<	* Return SnapshotEntry for results of findNear.
1459	>	* Returns SnapshotEntry for results of findNear.
1460		* @param kkey the key
1461		* @param rel the relation -- OR'ed combination of EQ, LT, GT
1462		* @return Entry fitting relation, or null if no such
#	Line 1410 | Line 1472 | public class ConcurrentSkipListMap<K,V>
1472		}
1473		}
1474
1475	+	/**
1476	+	* Returns ceiling, or first node if key is {@code null}.
1477	+	*/
1478	+	Node<K,V> findCeiling(K key) {
1479	+	return (key == null) ? findFirst() : findNear(key, GT|EQ);
1480	+	}
1481	+
1482	+	/**
1483	+	* Returns lower node, or last node if key is {@code null}.
1484	+	*/
1485	+	Node<K,V> findLower(K key) {
1486	+	return (key == null) ? findLast() : findNear(key, LT);
1487	+	}
1488	+
1489	+	/**
1490	+	* Returns 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 {@code null} 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	+	* Finds and removes 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 {@code null} 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	+	* Finds and removes 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 {@code null} 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 1425 | Line 1574 | public class ConcurrentSkipListMap<K,V>
1574		* Constructs a new empty map, sorted according to the given comparator.
1575		*
1576		* @param c the comparator that will be used to sort this map.  A
1577	<	*        <tt>null</tt> value indicates that the keys' <i>natural
1577	>	*        {@code null} value indicates that the keys' <i>natural
1578		*        ordering</i> should be used.
1579		*/
1580		public ConcurrentSkipListMap(Comparator<? super K> c) {
#	Line 1435 | 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.
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
1591	<	*         are not mutually comparable.
1592	<	* @throws NullPointerException if the specified map is null.
1591	>	*         are not mutually comparable
1592	>	* @throws NullPointerException if the specified map is {@code null}
1593		*/
1594		public ConcurrentSkipListMap(Map<? extends K, ? extends V> m) {
1595		this.comparator = null;
#	Line 1450 | 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 null.
1602	>	* {@code SortedMap}, 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	>	* {@code null}
1607		*/
1608		public ConcurrentSkipListMap(SortedMap<K, ? extends V> m) {
1609		this.comparator = m.comparator();
#	Line 1462 | Line 1612 | public class ConcurrentSkipListMap<K,V>
1612		}
1613
1614		/**
1615	<	* Returns a shallow copy of this <tt>Map</tt> instance. (The keys and
1615	>	* Returns a shallow copy of this {@code Map} instance. (The keys and
1616		* values themselves are not cloned.)
1617		*
1618	<	* @return a shallow copy of this Map.
1618	>	* @return a shallow copy of this Map
1619		*/
1620		public Object clone() {
1621		ConcurrentSkipListMap<K,V> clone = null;
#	Line 1497 | 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 1505 | 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 1521 | 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 1539 | Line 1689 | public class ConcurrentSkipListMap<K,V>
1689		/* ---------------- Serialization -------------- */
1690
1691		/**
1692	<	* Save the state of the <tt>Map</tt> instance to a stream.
1692	>	* Saves the state of the {@code Map} 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
1696	<	* <tt>null</tt>. The key-value mappings are emitted in key-order
1695	>	* key-value mapping represented by the Map, followed by
1696	>	* {@code null}. 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).
1699		*/
#	Line 1564 | Line 1714 | public class ConcurrentSkipListMap<K,V>
1714		}
1715
1716		/**
1717	<	* Reconstitute the <tt>Map</tt> instance from a stream.
1717	>	* Reconstitutes the {@code Map} instance from a stream.
1718		*/
1719		private void readObject(final java.io.ObjectInputStream s)
1720		throws java.io.IOException, ClassNotFoundException {
#	Line 1573 | 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 1584 | 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 1597 | 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 1609 | 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 1627 | Line 1777 | public class ConcurrentSkipListMap<K,V>
1777		/* ------ Map API methods ------ */
1778
1779		/**
1780	<	* Returns <tt>true</tt> if this map contains a mapping for the specified
1780	>	* Returns {@code true} if this map contains a mapping for the specified
1781		* key.
1782	<	* @param key key whose presence in this map is to be tested.
1783	<	* @return <tt>true</tt> if this map contains a mapping for the
1784	<	*            specified key.
1782	>	* @param key key whose presence in this map is to be tested
1783	>	* @return {@code true} if this map contains a mapping for the
1784	>	*            specified key
1785		* @throws ClassCastException if the key cannot be compared with the keys
1786	<	*                  currently in the map.
1787	<	* @throws NullPointerException if the key is <tt>null</tt>.
1786	>	*                  currently in the map
1787	>	* @throws NullPointerException if the key is {@code null}
1788		*/
1789		public boolean containsKey(Object key) {
1790		return doGet(key) != null;
#	Line 1642 | 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	>	* {@code null} if the map contains no mapping for this key.
1796		*
1797	<	* @param key key whose associated value is to be returned.
1797	>	* @param key key whose associated value is to be returned
1798		* @return the value to which this map maps the specified key, or
1799	<	*               <tt>null</tt> if the map contains no mapping for the key.
1799	>	*               {@code null} if the map contains no mapping for the key
1800		* @throws ClassCastException if the key cannot be compared with the keys
1801	<	*                  currently in the map.
1802	<	* @throws NullPointerException if the key is <tt>null</tt>.
1801	>	*                  currently in the map
1802	>	* @throws NullPointerException if the key is {@code null}
1803		*/
1804		public V get(Object key) {
1805		return doGet(key);
#	Line 1660 | Line 1810 | public class ConcurrentSkipListMap<K,V>
1810		* If the map previously contained a mapping for this key, the old
1811		* value is replaced.
1812		*
1813	<	* @param key key with which the specified value is to be associated.
1814	<	* @param value value to be associated with the specified key.
1813	>	* @param key key with which the specified value is to be associated
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.
1816	>	* @return previous value associated with specified key, or {@code null}
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>.
1819	>	*            currently in the map
1820	>	* @throws NullPointerException if the key or value are {@code null}
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 1679 | Line 1829 | public class ConcurrentSkipListMap<K,V>
1829		* Removes the mapping for this key from this Map if present.
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.
1832	>	* @return previous value associated with specified key, or {@code null}
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.
1837	<	* @throws NullPointerException if the key is <tt>null</tt>.
1836	>	*            currently in the map
1837	>	* @throws NullPointerException if the key is {@code null}
1838		*/
1839		public V remove(Object key) {
1840		return doRemove(key, null);
1841		}
1842
1843		/**
1844	<	* Returns <tt>true</tt> if this map maps one or more keys to the
1844	>	* Returns {@code true} if this map maps one or more keys to the
1845		* specified value.  This operation requires time linear in the
1846		* Map size.
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.
1851	<	* @throws  NullPointerException  if the value is <tt>null</tt>.
1852	<	*/
1848	>	* @param value value whose presence in this Map is to be tested
1849	>	* @return  {@code true} if a mapping to {@code value} exists;
1850	>	*          {@code false} otherwise
1851	>	* @throws  NullPointerException  if the value is {@code null}
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 1713 | Line 1863 | public class ConcurrentSkipListMap<K,V>
1863
1864		/**
1865		* Returns the number of elements in this map.  If this map
1866	<	* contains more than <tt>Integer.MAX_VALUE</tt> elements, it
1867	<	* returns <tt>Integer.MAX_VALUE</tt>.
1866	>	* contains more than {@code Integer.MAX_VALUE} elements, it
1867	>	* returns {@code Integer.MAX_VALUE}.
1868		*
1869		* <p>Beware that, unlike in most collections, this method is
1870		* <em>NOT</em> a constant-time operation. Because of the
#	Line 1725 | Line 1875 | public class ConcurrentSkipListMap<K,V>
1875		* will be inaccurate. Thus, this method is typically not very
1876		* useful in concurrent applications.
1877		*
1878	<	* @return  the number of elements in this map.
1878	>	* @return  the number of elements in this map
1879		*/
1880		public int size() {
1881		long count = 0;
#	Line 1733 | Line 1883 | public class ConcurrentSkipListMap<K,V>
1883		if (n.getValidValue() != null)
1884		++count;
1885		}
1886	<	return (count >= Integer.MAX_VALUE)? Integer.MAX_VALUE : (int)count;
1886	>	return (count >= Integer.MAX_VALUE) ? Integer.MAX_VALUE : (int)count;
1887		}
1888
1889		/**
1890	<	* Returns <tt>true</tt> if this map contains no key-value mappings.
1891	<	* @return <tt>true</tt> if this map contains no key-value mappings.
1890	>	* Returns {@code true} if this map contains no key-value mappings.
1891	>	* @return {@code true} if this map contains no key-value mappings
1892		*/
1893		public boolean isEmpty() {
1894		return findFirst() == null;
#	Line 1755 | Line 1905 | public class ConcurrentSkipListMap<K,V>
1905		* Returns a set view of the keys contained in this map.  The set is
1906		* backed by the map, so changes to the map are reflected in the set, and
1907		* vice-versa.  The set supports element removal, which removes the
1908	<	* corresponding mapping from this map, via the <tt>Iterator.remove</tt>,
1909	<	* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and
1910	<	* <tt>clear</tt> operations.  It does not support the <tt>add</tt> or
1911	<	* <tt>addAll</tt> operations.
1912	<	* The view's <tt>iterator</tt> is a "weakly consistent" iterator that
1908	>	* corresponding mapping from this map, via the {@code Iterator.remove},
1909	>	* {@code Set.remove}, {@code removeAll}, {@code retainAll}, and
1910	>	* {@code clear} operations.  It does not support the {@code add} or
1911	>	* {@code addAll} operations.
1912	>	* The view's {@code iterator} is a "weakly consistent" iterator that
1913		* will never throw {@link java.util.ConcurrentModificationException},
1914		* and guarantees to traverse elements as they existed upon
1915		* construction of the iterator, and may (but is not guaranteed to)
1916		* reflect any modifications subsequent to construction.
1917		*
1918	<	* @return a set view of the keys contained in this map.
1918	>	* @return a set view of the keys contained in this map
1919		*/
1920		public Set<K> keySet() {
1921		/*
#	Line 1782 | 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 {@code Iterator.remove},
1940	+	* {@code Set.remove}, {@code removeAll}, {@code retainAll},
1941	+	* and {@code clear} operations.  It does not support the
1942	+	* {@code add} or {@code addAll} operations.  The view's
1943	+	* {@code iterator} 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
1969		* supports element removal, which removes the corresponding
1970	<	* mapping from this map, via the <tt>Iterator.remove</tt>,
1971	<	* <tt>Collection.remove</tt>, <tt>removeAll</tt>,
1972	<	* <tt>retainAll</tt>, and <tt>clear</tt> operations.  It does not
1973	<	* support the <tt>add</tt> or <tt>addAll</tt> operations.  The
1974	<	* view's <tt>iterator</tt> is a "weakly consistent" iterator that
1970	>	* mapping from this map, via the {@code Iterator.remove},
1971	>	* {@code Collection.remove}, {@code removeAll},
1972	>	* {@code retainAll}, and {@code clear} operations.  It does not
1973	>	* support the {@code add} or {@code addAll} operations.  The
1974	>	* view's {@code iterator} is a "weakly consistent" iterator that
1975		* will never throw {@link
1976		* java.util.ConcurrentModificationException}, and guarantees to
1977		* traverse elements as they existed upon construction of the
1978		* iterator, and may (but is not guaranteed to) reflect any
1979		* modifications subsequent to construction.
1980		*
1981	<	* @return a collection view of the values contained in this map.
1981	>	* @return a collection view of the values contained in this map
1982		*/
1983		public Collection<V> values() {
1984		Values vs = values;
#	Line 1807 | Line 1988 | public class ConcurrentSkipListMap<K,V>
1988		/**
1989		* Returns a collection view of the mappings contained in this
1990		* map.  Each element in the returned collection is a
1991	<	* <tt>Map.Entry</tt>.  The collection is backed by the map, so
1991	>	* {@code Map.Entry}.  The collection is backed by the map, so
1992		* changes to the map are reflected in the collection, and
1993		* vice-versa.  The collection supports element removal, which
1994		* removes the corresponding mapping from the map, via the
1995	<	* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
1996	<	* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
1997	<	* operations.  It does not support the <tt>add</tt> or
1998	<	* <tt>addAll</tt> operations.  The view's <tt>iterator</tt> is a
1995	>	* {@code Iterator.remove}, {@code Collection.remove},
1996	>	* {@code removeAll}, {@code retainAll}, and {@code clear}
1997	>	* operations.  It does not support the {@code add} or
1998	>	* {@code addAll} operations.  The view's {@code iterator} is a
1999		* "weakly consistent" iterator that will never throw {@link
2000		* java.util.ConcurrentModificationException}, and guarantees to
2001		* traverse elements as they existed upon construction of the
2002		* iterator, and may (but is not guaranteed to) reflect any
2003		* modifications subsequent to construction. The
2004	<	* <tt>Map.Entry</tt> elements returned by
2005	<	* <tt>iterator.next()</tt> do <em>not</em> support the
2006	<	* <tt>setValue</tt> operation.
2004	>	* {@code Map.Entry} elements returned by
2005	>	* {@code iterator.next()} do <em>not</em> support the
2006	>	* {@code setValue} operation.
2007		*
2008	<	* @return a collection view of the mappings contained in this map.
2008	>	* @return a collection view of the mappings contained in this map
2009		*/
2010		public Set<Map.Entry<K,V>> entrySet() {
2011		EntrySet es = entrySet;
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 {@code Map.Entry}.  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 {@code Iterator.remove}, {@code Collection.remove},
2023	+	* {@code removeAll}, {@code retainAll}, and {@code clear}
2024	+	* operations.  It does not support the {@code add} or
2025	+	* {@code addAll} operations.  The view's {@code iterator} 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	+	* {@code Map.Entry} elements returned by
2032	+	* {@code iterator.next()} do <em>not</em> support the
2033	+	* {@code setValue} 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 {@code true} if the given object is also a map and the
2047	+	* two maps represent the same mappings.  More formally, two maps
2048	+	* {@code t1} and {@code t2} represent the same mappings if
2049	+	* {@code t1.keySet().equals(t2.keySet())} and for every key
2050	+	* {@code k} in {@code t1.keySet()}, {@code  (t1.get(k)==null ?
2051	+	* t2.get(k)==null : t1.get(k).equals(t2.get(k))) }.  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 {@code true} 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 1838 | 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))
2097	<	*      return map.put(key, value);
2096	>	*   if (!map.containsKey(key))
2097	>	*     return map.put(key, value);
2098		*   else
2099	<	*      return map.get(key);
2099	>	*     return map.get(key);
2100		* </pre>
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.
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 {@code null}
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>.
2108	>	*            currently in the map
2109	>	* @throws NullPointerException if the key or value are {@code null}
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		}
2116
2117		/**
2118	<	* Remove entry for key only if currently mapped to given value.
2118	>	* Removes 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;
2124		* } else return false;
2125		* </pre>
2126		* except that the action is performed atomically.
2127	<	* @param key key with which the specified value is associated.
2128	<	* @param value value associated with the specified key.
2127	>	* @param key key with which the specified value is associated
2128	>	* @param value value associated with the specified key
2129		* @return true if the value was removed, false otherwise
2130		* @throws ClassCastException if the key cannot be compared with the keys
2131	<	*            currently in the map.
2132	<	* @throws NullPointerException if the key or value are <tt>null</tt>.
2131	>	*            currently in the map
2132	>	* @throws NullPointerException if the key or value are {@code null}
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		}
2139
2140		/**
2141	<	* Replace entry for key only if currently mapped to given value.
2141	>	* Replaces 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;
2147		* } else return false;
2148		* </pre>
2149		* except that the action is performed atomically.
2150	<	* @param key key with which the specified value is associated.
2151	<	* @param oldValue value expected to be associated with the specified key.
2152	<	* @param newValue value to be associated with the specified key.
2150	>	* @param key key with which the specified value is associated
2151	>	* @param oldValue value expected to be associated with the specified key
2152	>	* @param newValue value to be associated with the specified key
2153		* @return true if the value was replaced
2154		* @throws ClassCastException if the key cannot be compared with the keys
2155	<	*            currently in the map.
2155	>	*            currently in the map
2156		* @throws NullPointerException if key, oldValue or newValue are
2157	<	* <tt>null</tt>.
2157	>	* {@code null}
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 1920 | Line 2175 | public class ConcurrentSkipListMap<K,V>
2175		}
2176
2177		/**
2178	<	* Replace entry for key only if currently mapped to some value.
2178	>	* Replaces 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;
2184		* </pre>
2185		* except that the action is performed atomically.
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.
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 {@code null}
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>.
2191	>	*            currently in the map
2192	>	* @throws NullPointerException if the key or value are {@code null}
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 1953 | Line 2208 | public class ConcurrentSkipListMap<K,V>
2208		/* ------ SortedMap API methods ------ */
2209
2210		/**
2211	<	* Returns the comparator used to order this map, or <tt>null</tt>
2211	>	* Returns the comparator used to order this map, or {@code null}
2212		* if this map uses its keys' natural order.
2213		*
2214		* @return the comparator associated with this map, or
2215	<	* <tt>null</tt> if it uses its keys' natural sort method.
2215	>	* {@code null} if it uses its keys' natural sort method
2216		*/
2217		public Comparator<? super K> comparator() {
2218		return comparator;
#	Line 1966 | Line 2221 | public class ConcurrentSkipListMap<K,V>
2221		/**
2222		* Returns the first (lowest) key currently in this map.
2223		*
2224	<	* @return the first (lowest) key currently in this map.
2225	<	* @throws    NoSuchElementException Map is empty.
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 1979 | Line 2234 | public class ConcurrentSkipListMap<K,V>
2234		/**
2235		* Returns the last (highest) key currently in this map.
2236		*
2237	<	* @return the last (highest) key currently in this map.
2238	<	* @throws    NoSuchElementException Map is empty.
2237	>	* @return the last (highest) key currently in this map
2238	>	* @throws    NoSuchElementException Map is empty
2239		*/
2240		public K lastKey() {
2241		Node<K,V> n = findLast();
#	Line 1991 | Line 2246 | public class ConcurrentSkipListMap<K,V>
2246
2247		/**
2248		* Returns a view of the portion of this map whose keys range from
2249	<	* <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive.  (If
2250	<	* <tt>fromKey</tt> and <tt>toKey</tt> are equal, the returned sorted map
2249	>	* {@code fromKey}, inclusive, to {@code toKey}, exclusive.  (If
2250	>	* {@code fromKey} and {@code toKey} are equal, the returned sorted map
2251		* is empty.)  The returned sorted map is backed by this map, so changes
2252		* in the returned sorted map are reflected in this map, and vice-versa.
2253	<
2254	<	* @param fromKey low endpoint (inclusive) of the subMap.
2255	<	* @param toKey high endpoint (exclusive) of the subMap.
2253	>	*
2254	>	* @param fromKey low endpoint (inclusive) of the subMap
2255	>	* @param toKey high endpoint (exclusive) of the subMap
2256		*
2257		* @return a view of the portion of this map whose keys range from
2258	<	* <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive.
2258	>	* {@code fromKey}, inclusive, to {@code toKey}, exclusive
2259		*
2260	<	* @throws ClassCastException if <tt>fromKey</tt> and <tt>toKey</tt>
2260	>	* @throws ClassCastException if {@code fromKey} and {@code toKey}
2261		*         cannot be compared to one another using this map's comparator
2262	<	*         (or, if the map has no comparator, using natural ordering).
2263	<	* @throws IllegalArgumentException if <tt>fromKey</tt> is greater than
2264	<	*         <tt>toKey</tt>.
2265	<	* @throws NullPointerException if <tt>fromKey</tt> or <tt>toKey</tt> is
2266	<	*               <tt>null</tt>.
2262	>	*         (or, if the map has no comparator, using natural ordering)
2263	>	* @throws IllegalArgumentException if {@code fromKey} is greater than
2264	>	*         {@code toKey}
2265	>	* @throws NullPointerException if {@code fromKey} or {@code toKey} is
2266	>	*               {@code null}
2267		*/
2268	<	public ConcurrentSkipListSubMap<K,V> subMap(K fromKey, K toKey) {
2268	>	public ConcurrentNavigableMap<K,V> subMap(K fromKey, K toKey) {
2269		if (fromKey == null || toKey == null)
2270		throw new NullPointerException();
2271		return new ConcurrentSkipListSubMap(this, fromKey, toKey);
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.
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>.
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>).
2286	<	* @throws NullPointerException if <tt>toKey</tt> is <tt>null</tt>.
2275	>	* Returns a view of the portion of this map whose keys are
2276	>	* strictly less than {@code toKey}.  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
2281	>	* strictly less than {@code toKey}
2282	>	*
2283	>	* @throws ClassCastException if {@code toKey} is not compatible
2284	>	* with this map's comparator (or, if the map has no comparator,
2285	>	* if {@code toKey} does not implement {@code Comparable})
2286	>	* @throws NullPointerException if {@code toKey} is {@code null}
2287		*/
2288	<	public ConcurrentSkipListSubMap<K,V> headMap(K toKey) {
2288	>	public ConcurrentNavigableMap<K,V> headMap(K toKey) {
2289		if (toKey == null)
2290		throw new NullPointerException();
2291		return new ConcurrentSkipListSubMap(this, null, toKey);
#	Line 2038 | Line 2293 | public class ConcurrentSkipListMap<K,V>
2293
2294		/**
2295		* Returns a view of the portion of this map whose keys are
2296	<	* greater than or equal to <tt>fromKey</tt>.  The returned sorted
2296	>	* greater than or equal to {@code fromKey}.  The returned sorted
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>).
2305	<	* @throws NullPointerException if <tt>fromKey</tt> is <tt>null</tt>.
2299	>	* @param fromKey low endpoint (inclusive) of the tailMap
2300	>	* @return a view of the portion of this map whose keys are
2301	>	* greater than or equal to {@code fromKey}
2302	>	* @throws ClassCastException if {@code fromKey} is not
2303	>	* compatible with this map's comparator (or, if the map has no
2304	>	* comparator, if {@code fromKey} does not implement
2305	>	* {@code Comparable})
2306	>	* @throws NullPointerException if {@code fromKey} is {@code null}
2307		*/
2308	<	public ConcurrentSkipListSubMap<K,V>  tailMap(K fromKey) {
2308	>	public ConcurrentNavigableMap<K,V> tailMap(K fromKey) {
2309		if (fromKey == null)
2310		throw new NullPointerException();
2311		return new ConcurrentSkipListSubMap(this, fromKey, null);
#	Line 2059 | 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 null if there is
2319	<	* no such entry. The returned entry does <em>not</em> support
2320	<	* the <tt>Entry.setValue</tt> method.
2321	<	*
2322	<	* @param key the key.
2323	<	* @return an Entry associated with ceiling of given key, or null
2324	<	* if there is no such Entry.
2325	<	* @throws ClassCastException if key cannot be compared with the keys
2326	<	*            currently in the map.
2327	<	* @throws NullPointerException if key is <tt>null</tt>.
2318	>	* greater than or equal to the given key, or {@code null} if
2319	>	* there is no such entry. The returned entry does <em>not</em>
2320	>	* support the {@code Entry.setValue} method.
2321	>	*
2322	>	* @param key the key
2323	>	* @return an Entry associated with ceiling of given key, or
2324	>	* {@code null} 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 {@code null}
2328		*/
2329		public Map.Entry<K,V> ceilingEntry(K key) {
2330		return getNear(key, GT|EQ);
2331		}
2332
2333		/**
2334	+	* Returns least key greater than or equal to the given key, or
2335	+	* {@code null} if there is no such key.
2336	+	*
2337	+	* @param key the key
2338	+	* @return the ceiling key, or {@code null}
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 {@code null}
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 null if there is no
2351	>	* key strictly less than the given key, or {@code null} if there is no
2352		* such entry. The returned entry does <em>not</em> support
2353	<	* the <tt>Entry.setValue</tt> method.
2354	<	*
2355	<	* @param key the key.
2353	>	* the {@code Entry.setValue} method.
2354	>	*
2355	>	* @param key the key
2356		* @return an Entry with greatest key less than the given
2357	<	* key, or null if there is no such Entry.
2357	>	* key, or {@code null} if there is no such Entry
2358		* @throws ClassCastException if key cannot be compared with the keys
2359	<	*            currently in the map.
2360	<	* @throws NullPointerException if key is <tt>null</tt>.
2359	>	*            currently in the map
2360	>	* @throws NullPointerException if key is {@code null}
2361		*/
2362		public Map.Entry<K,V> lowerEntry(K key) {
2363		return getNear(key, LT);
2364		}
2365
2366		/**
2367	<	* Returns a key-value mapping associated with the greatest
2368	<	* key less than or equal to the given key, or null if there is no
2369	<	* such entry. The returned entry does <em>not</em> support
2370	<	* the <tt>Entry.setValue</tt> method.
2371	<	*
2372	<	* @param key the key.
2101	<	* @return an Entry associated with floor of given key, or null
2102	<	* if there is no such Entry.
2367	>	* Returns the greatest key strictly less than the given key, or
2368	>	* {@code null} if there is no such key.
2369	>	*
2370	>	* @param key the key
2371	>	* @return the greatest key less than the given
2372	>	* key, or {@code null} 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>.
2374	>	*            currently in the map
2375	>	* @throws NullPointerException if key is {@code null}
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 {@code null} if there
2385	>	* is no such entry. The returned entry does <em>not</em> support
2386	>	* the {@code Entry.setValue} method.
2387	>	*
2388	>	* @param key the key
2389	>	* @return an Entry associated with floor of given key, or {@code null}
2390	>	* if there is no such Entry
2391	>	* @throws ClassCastException if key cannot be compared with the keys
2392	>	*            currently in the map
2393	>	* @throws NullPointerException if key is {@code null}
2394		*/
2395		public Map.Entry<K,V> floorEntry(K key) {
2396		return getNear(key, LT|EQ);
2397		}
2398
2399		/**
2400	<	* Returns a key-value mapping associated with the least
2401	<	* key strictly greater than the given key, or null if there is no
2402	<	* such entry. The returned entry does <em>not</em> support
2403	<	* the <tt>Entry.setValue</tt> method.
2404	<	*
2405	<	* @param key the key.
2400	>	* Returns the greatest key
2401	>	* less than or equal to the given key, or {@code null} if there
2402	>	* is no such key.
2403	>	*
2404	>	* @param key the key
2405	>	* @return the floor of given key, or {@code null} 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 {@code null}
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 {@code null} if there
2419	>	* is no such entry. The returned entry does <em>not</em> support
2420	>	* the {@code Entry.setValue} method.
2421	>	*
2422	>	* @param key the key
2423		* @return an Entry with least key greater than the given key, or
2424	<	* null if there is no such Entry.
2424	>	* {@code null} if there is no such Entry
2425		* @throws ClassCastException if key cannot be compared with the keys
2426	<	*            currently in the map.
2427	<	* @throws NullPointerException if key is <tt>null</tt>.
2426	>	*            currently in the map
2427	>	* @throws NullPointerException if key is {@code null}
2428		*/
2429		public Map.Entry<K,V> higherEntry(K key) {
2430		return getNear(key, GT);
2431		}
2432
2433		/**
2434	+	* Returns the least key strictly greater than the given key, or
2435	+	* {@code null} if there is no such key.
2436	+	*
2437	+	* @param key the key
2438	+	* @return the least key greater than the given key, or
2439	+	* {@code null} 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 {@code null}
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 null if the map is empty.
2451	>	* key in this map, or {@code null} 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 null
2456	<	* if the map is empty.
2453	>	* the {@code Entry.setValue} method.
2454	>	*
2455	>	* @return an Entry with least key, or {@code null}
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 2147 | Line 2468 | public class ConcurrentSkipListMap<K,V>
2468
2469		/**
2470		* Returns a key-value mapping associated with the greatest
2471	<	* key in this map, or null if the map is empty.
2471	>	* key in this map, or {@code null} if the map is empty.
2472		* The returned entry does <em>not</em> support
2473	<	* the <tt>Entry.setValue</tt> method.
2474	<	*
2475	<	* @return an Entry with greatest key, or null
2476	<	* if the map is empty.
2473	>	* the {@code Entry.setValue} method.
2474	>	*
2475	>	* @return an Entry with greatest key, or {@code null}
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 2167 | Line 2488 | public class ConcurrentSkipListMap<K,V>
2488
2489		/**
2490		* Removes and returns a key-value mapping associated with
2491	<	* the least key in this map, or null if the map is empty.
2491	>	* the least key in this map, or {@code null} if the map is empty.
2492		* The returned entry does <em>not</em> support
2493	<	* the <tt>Entry.setValue</tt> method.
2494	<	*
2495	<	* @return the removed first entry of this map, or null
2496	<	* if the map is empty.
2493	>	* the {@code Entry.setValue} method.
2494	>	*
2495	>	* @return the removed first entry of this map, or {@code null}
2496	>	* if the map is empty
2497		*/
2498	<	public Map.Entry<K,V> removeFirstEntry() {
2499	<	return doRemoveFirstEntry();
2498	>	public Map.Entry<K,V> pollFirstEntry() {
2499	>	return (SnapshotEntry<K,V>)doRemoveFirst(false);
2500		}
2501
2502	+	/**
2503	+	* Removes and returns a key-value mapping associated with
2504	+	* the greatest key in this map, or {@code null} if the map is empty.
2505	+	* The returned entry does <em>not</em> support
2506	+	* the {@code Entry.setValue} method.
2507	+	*
2508	+	* @return the removed last entry of this map, or {@code null}
2509	+	* if the map is empty
2510	+	*/
2511	+	public Map.Entry<K,V> pollLastEntry() {
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 2204 | 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 null, but not greater or equal to
2552	<	* fence, or end if fence is null.
2549	>	/**
2550	>	* initialize ascending iterator starting at given least key,
2551	>	* or first node if least is {@code null}, but not greater or
2552	>	* equal to fence, or end if fence is {@code null}.
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;
2560	>	if (nextValue != null && nextValue != next) {
2561	>	if (fence != null && compare(fence, next.key) <= 0) {
2562	>	next = null;
2563	>	nextValue = null;
2564	>	}
2565	>	break;
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	>	/**
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;
#	Line 2225 | Line 2601 | public class ConcurrentSkipListMap<K,V>
2601		}
2602		}
2603
2604	<	public final boolean hasNext() {
2605	<	return next != null;
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	<	final void advance() {
2616	>	/**
2617	>	* initialize descending iterator starting at key less
2618	>	* than or equal to given fence key, or
2619	>	* last node if fence is {@code null}, but not less than
2620	>	* least, or beginning if lest is {@code null}.
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 2243 | 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 2271 | 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	>	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	<	advance();
2756	>	descend(least);
2757		return n.key;
2758		}
2759		}
#	Line 2296 | 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
2300	<	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() {
2305	<	super();
2306	<	}
2307	<
2308	<	EntryIterator(K least, K fence) {
2309	<	super(least, fence);
2310	<	}
2311	<
2312	<	public Map.Entry<K,V> next() {
2313	<	lastValue = nextValue;
2314	<	advance();
2315	<	return this;
2770	>	EntryIter() {
2771		}
2772
2773		public K getKey() {
#	Line 2326 | 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 2355 | 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) {
2384	<	super(least, fence);
2385	<	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);
2391	<	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
2410	–	/* ---------------- Utilities for views, sets, submaps -------------- */
2411	–
2871		// Factory methods for iterators needed by submaps and/or
2872		// ConcurrentSkipListSet
2873
#	Line 2416 | 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);
2878	>	Iterator<K> descendingKeyIterator() {
2879	>	return new DescendingKeyIterator();
2880		}
2881
2882	<	SubMapKeyIterator subMapKeyIterator(K least, K fence) {
2883	<	return new SubMapKeyIterator(least, fence);
2425	<	}
2426	<
2427	<	SubMapValueIterator subMapValueIterator(K least, K fence) {
2428	<	return new SubMapValueIterator(least, fence);
2429	<	}
2430	<
2431	<
2432	<	/**
2433	<	* Version of remove with boolean return. Needed by
2434	<	* view classes and ConcurrentSkipListSet
2435	<	*/
2436	<	boolean removep(Object key) {
2437	<	return doRemove(key, null) != null;
2438	<	}
2439	<
2440	<	/**
2441	<	* Return SnapshotEntry for results of findNear ofter screening
2442	<	* to ensure result is in given range. Needed by submaps.
2443	<	* @param kkey the key
2444	<	* @param rel the relation -- OR'ed combination of EQ, LT, GT
2445	<	* @param least minimum allowed key value
2446	<	* @param fence key greater than maximum allowed key value
2447	<	* @return Entry fitting relation, or null if no such
2448	<	*/
2449	<	SnapshotEntry<K,V> getNear(K kkey, int rel, K least, K fence) {
2450	<	K key = kkey;
2451	<	// Don't return keys less than least
2452	<	if ((rel & LT) == 0) {
2453	<	if (compare(key, least) < 0) {
2454	<	key = least;
2455	<	rel = rel | EQ;
2456	<	}
2457	<	}
2458	<
2459	<	for (;;) {
2460	<	Node<K,V> n = findNear(key, rel);
2461	<	if (n == null || !inHalfOpenRange(n.key, least, fence))
2462	<	return null;
2463	<	SnapshotEntry<K,V> e = n.createSnapshot();
2464	<	if (e != null)
2465	<	return e;
2466	<	}
2467	<	}
2468	<
2469	<	// Methods expanding out relational operations for submaps
2470	<
2471	<	/**
2472	<	* Return ceiling, or first node if key is null
2473	<	*/
2474	<	Node<K,V> findCeiling(K key) {
2475	<	return (key == null)? findFirst() : findNear(key, GT|EQ);
2476	<	}
2477	<
2478	<	/**
2479	<	* Return lower node, or last node if key is null
2480	<	*/
2481	<	Node<K,V> findLower(K key) {
2482	<	return (key == null)? findLast() : findNear(key, LT);
2483	<	}
2484	<
2485	<	/**
2486	<	* Find and remove least element of subrange.
2487	<	*/
2488	<	SnapshotEntry<K,V> removeFirstEntryOfSubrange(K least, K fence) {
2489	<	for (;;) {
2490	<	Node<K,V> n = findCeiling(least);
2491	<	if (n == null)
2492	<	return null;
2493	<	K k = n.key;
2494	<	if (fence != null && compare(k, fence) >= 0)
2495	<	return null;
2496	<	V v = doRemove(k, null);
2497	<	if (v != null)
2498	<	return new SnapshotEntry<K,V>(k,v);
2499	<	}
2500	<	}
2501	<
2502	<	SnapshotEntry<K,V> getCeiling(K key, K least, K fence) {
2503	<	return getNear(key, GT|EQ, least, fence);
2504	<	}
2505	<
2506	<	SnapshotEntry<K,V> getLower(K key, K least, K fence) {
2507	<	return getNear(key, LT, least, fence);
2508	<	}
2509	<
2510	<	SnapshotEntry<K,V> getFloor(K key, K least, K fence) {
2511	<	return getNear(key, LT|EQ, least, fence);
2512	<	}
2513	<
2514	<	SnapshotEntry<K,V> getHigher(K key, K least, K fence) {
2515	<	return getNear(key, GT, least, fence);
2516	<	}
2517	<
2518	<	// Key-returning relational methods for ConcurrentSkipListSet
2519	<
2520	<	K ceilingKey(K key) {
2521	<	Node<K,V> n = findNear(key, GT|EQ);
2522	<	return (n == null)? null : n.key;
2523	<	}
2524	<
2525	<	K lowerKey(K key) {
2526	<	Node<K,V> n = findNear(key, LT);
2527	<	return (n == null)? null : n.key;
2882	>	SubMapEntryIterator subMapEntryIterator(K least, K fence) {
2883	>	return new SubMapEntryIterator(least, fence);
2884		}
2885
2886	<	K floorKey(K key) {
2887	<	Node<K,V> n = findNear(key, LT|EQ);
2532	<	return (n == null)? null : n.key;
2886	>	DescendingSubMapEntryIterator descendingSubMapEntryIterator(K least, K fence) {
2887	>	return new DescendingSubMapEntryIterator(least, fence);
2888		}
2889
2890	<	K higherKey(K key) {
2891	<	Node<K,V> n = findNear(key, GT);
2537	<	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();
2542	<	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();
2547	<	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 2582 | 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 2613 | 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 2628 | 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 2642 | 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();
2647	<	if (e != null)
2648	<	c.add(e);
2649	<	}
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) {
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
3024	>	* maps. Instances of this class support all methods of their
3025	>	* underlying maps, differing in that mappings outside their range are
3026	>	* ignored, and attempts to add mappings outside their ranges result
3027	>	* in {@link IllegalArgumentException}.  Instances of this class are
3028	>	* constructed only using the {@code subMap}, {@code headMap}, and
3029	>	* {@code tailMap} methods of their underlying maps.
3030	>	*/
3031	>	static class ConcurrentSkipListSubMap<K,V> extends AbstractMap<K,V>
3032	>	implements ConcurrentNavigableMap<K,V>, java.io.Serializable {
3033	>
3034	>	private static final long serialVersionUID = -7647078645895051609L;
3035	>
3036	>	/** Underlying map */
3037	>	private final ConcurrentSkipListMap<K,V> m;
3038	>	/** lower bound key, or null if from start */
3039	>	private final K least;
3040	>	/** upper fence key, or null if to end */
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.
3051	>	* @param least inclusive least value, or {@code null} if from start
3052	>	* @param fence exclusive upper bound or {@code null} if to end
3053	>	* @throws IllegalArgumentException if least and fence non-null
3054	>	*  and least greater than fence
3055	>	*/
3056	>	ConcurrentSkipListSubMap(ConcurrentSkipListMap<K,V> map,
3057	>	K least, K fence) {
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;
3064	>	this.fence = fence;
3065	>	}
3066	>
3067	>	/* ----------------  Utilities -------------- */
3068	>
3069	>	boolean inHalfOpenRange(K key) {
3070	>	return m.inHalfOpenRange(key, least, fence);
3071	>	}
3072	>
3073	>	boolean inOpenRange(K key) {
3074	>	return m.inOpenRange(key, least, fence);
3075	>	}
3076	>
3077	>	ConcurrentSkipListMap.Node<K,V> firstNode() {
3078	>	return m.findCeiling(least);
3079	>	}
3080	>
3081	>	ConcurrentSkipListMap.Node<K,V> lastNode() {
3082	>	return m.findLower(fence);
3083	>	}
3084	>
3085	>	boolean isBeforeEnd(ConcurrentSkipListMap.Node<K,V> n) {
3086	>	return (n != null &&
3087	>	(fence == null ||
3088	>	n.key == null || // pass by markers and headers
3089	>	m.compare(fence, n.key) > 0));
3090	>	}
3091	>
3092	>	void checkKey(K key) throws IllegalArgumentException {
3093	>	if (!inHalfOpenRange(key))
3094	>	throw new IllegalArgumentException("key out of range");
3095	>	}
3096	>
3097	>	/**
3098	>	* Returns underlying map. Needed by ConcurrentSkipListSet.
3099	>	* @return the backing map
3100	>	*/
3101	>	ConcurrentSkipListMap<K,V> getMap() {
3102	>	return m;
3103	>	}
3104	>
3105	>	/**
3106	>	* Returns least key. Needed by ConcurrentSkipListSet.
3107	>	* @return least key or {@code null} if from start
3108	>	*/
3109	>	K getLeast() {
3110	>	return least;
3111	>	}
3112	>
3113	>	/**
3114	>	* Returns fence key. Needed by ConcurrentSkipListSet.
3115	>	* @return fence key or {@code null} of to end
3116	>	*/
3117	>	K getFence() {
3118	>	return fence;
3119	>	}
3120	>
3121	>
3122	>	/* ----------------  Map API methods -------------- */
3123	>
3124	>	public boolean containsKey(Object key) {
3125	>	K k = (K)key;
3126	>	return inHalfOpenRange(k) && m.containsKey(k);
3127	>	}
3128	>
3129	>	public V get(Object key) {
3130	>	K k = (K)key;
3131	>	return (!inHalfOpenRange(k)) ? null : m.get(k);
3132	>	}
3133	>
3134	>	public V put(K key, V value) {
3135	>	checkKey(key);
3136	>	return m.put(key, value);
3137	>	}
3138	>
3139	>	public V remove(Object key) {
3140	>	K k = (K)key;
3141	>	return (!inHalfOpenRange(k)) ? null : m.remove(k);
3142	>	}
3143	>
3144	>	public int size() {
3145	>	long count = 0;
3146	>	for (ConcurrentSkipListMap.Node<K,V> n = firstNode();
3147	>	isBeforeEnd(n);
3148	>	n = n.next) {
3149	>	if (n.getValidValue() != null)
3150	>	++count;
3151	>	}
3152	>	return (count >= Integer.MAX_VALUE) ?
3153	>	Integer.MAX_VALUE : (int)count;
3154	>	}
3155	>
3156	>	public boolean isEmpty() {
3157	>	return !isBeforeEnd(firstNode());
3158	>	}
3159	>
3160	>	public boolean containsValue(Object value) {
3161	>	if (value == null)
3162	>	throw new NullPointerException();
3163	>	for (ConcurrentSkipListMap.Node<K,V> n = firstNode();
3164	>	isBeforeEnd(n);
3165	>	n = n.next) {
3166	>	V v = n.getValidValue();
3167	>	if (v != null && value.equals(v))
3168	>	return true;
3169	>	}
3170	>	return false;
3171	>	}
3172	>
3173	>	public void clear() {
3174	>	for (ConcurrentSkipListMap.Node<K,V> n = firstNode();
3175	>	isBeforeEnd(n);
3176	>	n = n.next) {
3177	>	if (n.getValidValue() != null)
3178	>	m.remove(n.key);
3179	>	}
3180	>	}
3181	>
3182	>	/* ----------------  ConcurrentMap API methods -------------- */
3183	>
3184	>	public V putIfAbsent(K key, V value) {
3185	>	checkKey(key);
3186	>	return m.putIfAbsent(key, value);
3187	>	}
3188	>
3189	>	public boolean remove(Object key, Object value) {
3190	>	K k = (K)key;
3191	>	return inHalfOpenRange(k) && m.remove(k, value);
3192	>	}
3193	>
3194	>	public boolean replace(K key, V oldValue, V newValue) {
3195	>	checkKey(key);
3196	>	return m.replace(key, oldValue, newValue);
3197	>	}
3198	>
3199	>	public V replace(K key, V value) {
3200	>	checkKey(key);
3201	>	return m.replace(key, value);
3202	>	}
3203	>
3204	>	/* ----------------  SortedMap API methods -------------- */
3205	>
3206	>	public Comparator<? super K> comparator() {
3207	>	return m.comparator();
3208	>	}
3209	>
3210	>	public K firstKey() {
3211	>	ConcurrentSkipListMap.Node<K,V> n = firstNode();
3212	>	if (isBeforeEnd(n))
3213	>	return n.key;
3214	>	else
3215	>	throw new NoSuchElementException();
3216	>	}
3217	>
3218	>	public K lastKey() {
3219	>	ConcurrentSkipListMap.Node<K,V> n = lastNode();
3220	>	if (n != null) {
3221	>	K last = n.key;
3222	>	if (inHalfOpenRange(last))
3223	>	return last;
3224	>	}
3225	>	throw new NoSuchElementException();
3226	>	}
3227	>
3228	>	public ConcurrentNavigableMap<K,V> subMap(K fromKey, K toKey) {
3229	>	if (fromKey == null || toKey == null)
3230	>	throw new NullPointerException();
3231	>	if (!inOpenRange(fromKey) || !inOpenRange(toKey))
3232	>	throw new IllegalArgumentException("key out of range");
3233	>	return new ConcurrentSkipListSubMap(m, fromKey, toKey);
3234	>	}
3235	>
3236	>	public ConcurrentNavigableMap<K,V> headMap(K toKey) {
3237	>	if (toKey == null)
3238	>	throw new NullPointerException();
3239	>	if (!inOpenRange(toKey))
3240	>	throw new IllegalArgumentException("key out of range");
3241	>	return new ConcurrentSkipListSubMap(m, least, toKey);
3242	>	}
3243	>
3244	>	public ConcurrentNavigableMap<K,V> tailMap(K fromKey) {
3245	>	if (fromKey == null)
3246	>	throw new NullPointerException();
3247	>	if (!inOpenRange(fromKey))
3248	>	throw new IllegalArgumentException("key out of range");
3249	>	return new ConcurrentSkipListSubMap(m, fromKey, fence);
3250	>	}
3251	>
3252	>	/* ----------------  Relational methods -------------- */
3253	>
3254	>	public Map.Entry<K,V> ceilingEntry(K key) {
3255	>	return (SnapshotEntry<K,V>)
3256	>	m.getNear(key, GT|EQ, least, fence, false);
3257	>	}
3258	>
3259	>	public K ceilingKey(K key) {
3260	>	return (K)
3261	>	m.getNear(key, GT|EQ, least, fence, true);
3262	>	}
3263	>
3264	>	public Map.Entry<K,V> lowerEntry(K key) {
3265	>	return (SnapshotEntry<K,V>)
3266	>	m.getNear(key, LT, least, fence, false);
3267	>	}
3268	>
3269	>	public K lowerKey(K key) {
3270	>	return (K)
3271	>	m.getNear(key, LT, least, fence, true);
3272	>	}
3273	>
3274	>	public Map.Entry<K,V> floorEntry(K key) {
3275	>	return (SnapshotEntry<K,V>)
3276	>	m.getNear(key, LT|EQ, least, fence, false);
3277	>	}
3278	>
3279	>	public K floorKey(K key) {
3280	>	return (K)
3281	>	m.getNear(key, LT|EQ, least, fence, true);
3282	>	}
3283	>
3284	>
3285	>	public Map.Entry<K,V> higherEntry(K key) {
3286	>	return (SnapshotEntry<K,V>)
3287	>	m.getNear(key, GT, least, fence, false);
3288	>	}
3289	>
3290	>	public K higherKey(K key) {
3291	>	return (K)
3292	>	m.getNear(key, GT, least, fence, true);
3293	>	}
3294	>
3295	>	public Map.Entry<K,V> firstEntry() {
3296	>	for (;;) {
3297	>	ConcurrentSkipListMap.Node<K,V> n = firstNode();
3298	>	if (!isBeforeEnd(n))
3299	>	return null;
3300		Map.Entry<K,V> e = n.createSnapshot();
3301	<	if (e != null)
3302	<	c.add(e);
3301	>	if (e != null)
3302	>	return e;
3303	>	}
3304	>	}
3305	>
3306	>	public Map.Entry<K,V> lastEntry() {
3307	>	for (;;) {
3308	>	ConcurrentSkipListMap.Node<K,V> n = lastNode();
3309	>	if (n == null || !inHalfOpenRange(n.key))
3310	>	return null;
3311	>	Map.Entry<K,V> e = n.createSnapshot();
3312	>	if (e != null)
3313	>	return e;
3314	>	}
3315	>	}
3316	>
3317	>	public Map.Entry<K,V> pollFirstEntry() {
3318	>	return (SnapshotEntry<K,V>)
3319	>	m.removeFirstEntryOfSubrange(least, fence, false);
3320	>	}
3321	>
3322	>	public Map.Entry<K,V> pollLastEntry() {
3323	>	return (SnapshotEntry<K,V>)
3324	>	m.removeLastEntryOfSubrange(least, fence, false);
3325	>	}
3326	>
3327	>	/* ---------------- Submap Views -------------- */
3328	>
3329	>	public Set<K> keySet() {
3330	>	Set<K> ks = keySetView;
3331	>	return (ks != null) ? ks : (keySetView = new KeySetView());
3332	>	}
3333	>
3334	>	class KeySetView extends AbstractSet<K> {
3335	>	public Iterator<K> iterator() {
3336	>	return m.subMapKeyIterator(least, fence);
3337	>	}
3338	>	public int size() {
3339	>	return ConcurrentSkipListSubMap.this.size();
3340	>	}
3341	>	public boolean isEmpty() {
3342	>	return ConcurrentSkipListSubMap.this.isEmpty();
3343	>	}
3344	>	public boolean contains(Object k) {
3345	>	return ConcurrentSkipListSubMap.this.containsKey(k);
3346	>	}
3347	>	public Object[] toArray() {
3348	>	Collection<K> c = new ArrayList<K>();
3349	>	for (Iterator<K> i = iterator(); i.hasNext(); )
3350	>	c.add(i.next());
3351	>	return c.toArray();
3352	>	}
3353	>	public <T> T[] toArray(T[] a) {
3354	>	Collection<K> c = new ArrayList<K>();
3355	>	for (Iterator<K> i = iterator(); i.hasNext(); )
3356	>	c.add(i.next());
3357	>	return c.toArray(a);
3358	>	}
3359	>	}
3360	>
3361	>	public Set<K> descendingKeySet() {
3362	>	Set<K> ks = descendingKeySetView;
3363	>	return (ks != null) ? ks : (descendingKeySetView = new DescendingKeySetView());
3364	>	}
3365	>
3366	>	class DescendingKeySetView extends KeySetView {
3367	>	public Iterator<K> iterator() {
3368	>	return m.descendingSubMapKeyIterator(least, fence);
3369	>	}
3370	>	}
3371	>
3372	>	public Collection<V> values() {
3373	>	Collection<V> vs = valuesView;
3374	>	return (vs != null) ? vs : (valuesView = new ValuesView());
3375	>	}
3376	>
3377	>	class ValuesView extends AbstractCollection<V> {
3378	>	public Iterator<V> iterator() {
3379	>	return m.subMapValueIterator(least, fence);
3380	>	}
3381	>	public int size() {
3382	>	return ConcurrentSkipListSubMap.this.size();
3383	>	}
3384	>	public boolean isEmpty() {
3385	>	return ConcurrentSkipListSubMap.this.isEmpty();
3386	>	}
3387	>	public boolean contains(Object v) {
3388	>	return ConcurrentSkipListSubMap.this.containsValue(v);
3389	>	}
3390	>	public Object[] toArray() {
3391	>	Collection<V> c = new ArrayList<V>();
3392	>	for (Iterator<V> i = iterator(); i.hasNext(); )
3393	>	c.add(i.next());
3394	>	return c.toArray();
3395	>	}
3396	>	public <T> T[] toArray(T[] a) {
3397	>	Collection<V> c = new ArrayList<V>();
3398	>	for (Iterator<V> i = iterator(); i.hasNext(); )
3399	>	c.add(i.next());
3400	>	return c.toArray(a);
3401	>	}
3402	>	}
3403	>
3404	>	public Set<Map.Entry<K,V>> entrySet() {
3405	>	Set<Map.Entry<K,V>> es = entrySetView;
3406	>	return (es != null) ? es : (entrySetView = new EntrySetView());
3407	>	}
3408	>
3409	>	class EntrySetView extends AbstractSet<Map.Entry<K,V>> {
3410	>	public Iterator<Map.Entry<K,V>> iterator() {
3411	>	return m.subMapEntryIterator(least, fence);
3412	>	}
3413	>	public int size() {
3414	>	return ConcurrentSkipListSubMap.this.size();
3415	>	}
3416	>	public boolean isEmpty() {
3417	>	return ConcurrentSkipListSubMap.this.isEmpty();
3418	>	}
3419	>	public boolean contains(Object o) {
3420	>	if (!(o instanceof Map.Entry))
3421	>	return false;
3422	>	Map.Entry<K,V> e = (Map.Entry<K,V>) o;
3423	>	K key = e.getKey();
3424	>	if (!inHalfOpenRange(key))
3425	>	return false;
3426	>	V v = m.get(key);
3427	>	return v != null && v.equals(e.getValue());
3428	>	}
3429	>	public boolean remove(Object o) {
3430	>	if (!(o instanceof Map.Entry))
3431	>	return false;
3432	>	Map.Entry<K,V> e = (Map.Entry<K,V>) o;
3433	>	K key = e.getKey();
3434	>	if (!inHalfOpenRange(key))
3435	>	return false;
3436	>	return m.remove(key, e.getValue());
3437	>	}
3438	>	public Object[] toArray() {
3439	>	Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>();
3440	>	for (Map.Entry e : this)
3441	>	c.add(new SnapshotEntry(e.getKey(), e.getValue()));
3442	>	return c.toArray();
3443	>	}
3444	>	public <T> T[] toArray(T[] a) {
3445	>	Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>();
3446	>	for (Map.Entry e : this)
3447	>	c.add(new SnapshotEntry(e.getKey(), e.getValue()));
3448	>	return c.toArray(a);
3449	>	}
3450	>	}
3451	>
3452	>	public Set<Map.Entry<K,V>> descendingEntrySet() {
3453	>	Set<Map.Entry<K,V>> es = descendingEntrySetView;
3454	>	return (es != null) ? es : (descendingEntrySetView = new DescendingEntrySetView());
3455	>	}
3456	>
3457	>	class DescendingEntrySetView extends EntrySetView {
3458	>	public Iterator<Map.Entry<K,V>> iterator() {
3459	>	return m.descendingSubMapEntryIterator(least, fence);
3460		}
2659	–	return c.toArray(a);
3461		}
3462		}
3463		}

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