util/concurrent/ConcurrentSkipListSet.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package java.util.concurrent;
import java.util.*;
import java.util.Spliterator;
import java.util.stream.Stream;
import java.util.stream.Streams;

/**
 * A scalable concurrent {@link NavigableSet} implementation based on
 * a {@link ConcurrentSkipListMap}.  The elements of the set are kept
 * sorted according to their {@linkplain Comparable natural ordering},
 * or by a {@link Comparator} provided at set creation time, depending
 * on which constructor is used.
 *
 * <p>This implementation provides expected average <i>log(n)</i> time
 * cost for the {@code contains}, {@code add}, and {@code remove}
 * operations and their variants.  Insertion, removal, and access
 * operations safely execute concurrently by multiple threads.
 * Iterators are <i>weakly consistent</i>, returning elements
 * reflecting the state of the set at some point at or since the
 * creation of the iterator.  They do <em>not</em> throw {@link
 * ConcurrentModificationException}, and may proceed concurrently with
 * other operations.  Ascending ordered views and their iterators are
 * faster than descending ones.
 *
 * <p>Beware that, unlike in most collections, the {@code size}
 * method is <em>not</em> a constant-time operation. Because of the
 * asynchronous nature of these sets, determining the current number
 * of elements requires a traversal of the elements, and so may report
 * inaccurate results if this collection is modified during traversal.
 * Additionally, the bulk operations {@code addAll},
 * {@code removeAll}, {@code retainAll}, {@code containsAll},
 * {@code equals}, and {@code toArray} are <em>not</em> guaranteed
 * to be performed atomically. For example, an iterator operating
 * concurrently with an {@code addAll} operation might view only some
 * of the added elements.
 *
 * <p>This class and its iterators implement all of the
 * <em>optional</em> methods of the {@link Set} and {@link Iterator}
 * interfaces. Like most other concurrent collection implementations,
 * this class does not permit the use of {@code null} elements,
 * because {@code null} arguments and return values cannot be reliably
 * distinguished from the absence of elements.
 *
 * <p>This class is a member of the
 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @author Doug Lea
 * @param <E> the type of elements maintained by this set
 * @since 1.6
 */
public class ConcurrentSkipListSet<E>
    extends AbstractSet<E>
    implements NavigableSet<E>, Cloneable, java.io.Serializable {

    private static final long serialVersionUID = -2479143111061671589L;

    /**
     * The underlying map. Uses Boolean.TRUE as value for each
     * element.  This field is declared final for the sake of thread
     * safety, which entails some ugliness in clone()
     */
    private final ConcurrentNavigableMap<E,Object> m;

    /**
     * Constructs a new, empty set that orders its elements according to
     * their {@linkplain Comparable natural ordering}.
     */
    public ConcurrentSkipListSet() {
        m = new ConcurrentSkipListMap<E,Object>();
    }

    /**
     * Constructs a new, empty set that orders its elements according to
     * the specified comparator.
     *
     * @param comparator the comparator that will be used to order this set.
     *        If {@code null}, the {@linkplain Comparable natural
     *        ordering} of the elements will be used.
     */
    public ConcurrentSkipListSet(Comparator<? super E> comparator) {
        m = new ConcurrentSkipListMap<E,Object>(comparator);
    }

    /**
     * Constructs a new set containing the elements in the specified
     * collection, that orders its elements according to their
     * {@linkplain Comparable natural ordering}.
     *
     * @param c The elements that will comprise the new set
     * @throws ClassCastException if the elements in {@code c} are
     *         not {@link Comparable}, or are not mutually comparable
     * @throws NullPointerException if the specified collection or any
     *         of its elements are null
     */
    public ConcurrentSkipListSet(Collection<? extends E> c) {
        m = new ConcurrentSkipListMap<E,Object>();
        addAll(c);
    }

    /**
     * Constructs a new set containing the same elements and using the
     * same ordering as the specified sorted set.
     *
     * @param s sorted set whose elements will comprise the new set
     * @throws NullPointerException if the specified sorted set or any
     *         of its elements are null
     */
    public ConcurrentSkipListSet(SortedSet<E> s) {
        m = new ConcurrentSkipListMap<E,Object>(s.comparator());
        addAll(s);
    }

    /**
     * For use by submaps
     */
    ConcurrentSkipListSet(ConcurrentNavigableMap<E,Object> m) {
        this.m = m;
    }

    /**
     * Returns a shallow copy of this {@code ConcurrentSkipListSet}
     * instance. (The elements themselves are not cloned.)
     *
     * @return a shallow copy of this set
     */
    public ConcurrentSkipListSet<E> clone() {
        try {
            @SuppressWarnings("unchecked")
            ConcurrentSkipListSet<E> clone =
                (ConcurrentSkipListSet<E>) super.clone();
            clone.setMap(new ConcurrentSkipListMap<E,Object>(m));
            return clone;
        } catch (CloneNotSupportedException e) {
            throw new InternalError();
        }
    }

    /* ---------------- Set operations -------------- */

    /**
     * Returns the number of elements in this set.  If this set
     * contains more than {@code Integer.MAX_VALUE} elements, it
     * returns {@code Integer.MAX_VALUE}.
     *
     * <p>Beware that, unlike in most collections, this method is
     * <em>NOT</em> a constant-time operation. Because of the
     * asynchronous nature of these sets, determining the current
     * number of elements requires traversing them all to count them.
     * Additionally, it is possible for the size to change during
     * execution of this method, in which case the returned result
     * will be inaccurate. Thus, this method is typically not very
     * useful in concurrent applications.
     *
     * @return the number of elements in this set
     */
    public int size() {
        return m.size();
    }

    /**
     * Returns {@code true} if this set contains no elements.
     * @return {@code true} if this set contains no elements
     */
    public boolean isEmpty() {
        return m.isEmpty();
    }

    /**
     * Returns {@code true} if this set contains the specified element.
     * More formally, returns {@code true} if and only if this set
     * contains an element {@code e} such that {@code o.equals(e)}.
     *
     * @param o object to be checked for containment in this set
     * @return {@code true} if this set contains the specified element
     * @throws ClassCastException if the specified element cannot be
     *         compared with the elements currently in this set
     * @throws NullPointerException if the specified element is null
     */
    public boolean contains(Object o) {
        return m.containsKey(o);
    }

    /**
     * Adds the specified element to this set if it is not already present.
     * More formally, adds the specified element {@code e} to this set if
     * the set contains no element {@code e2} such that {@code e.equals(e2)}.
     * If this set already contains the element, the call leaves the set
     * unchanged and returns {@code false}.
     *
     * @param e element to be added to this set
     * @return {@code true} if this set did not already contain the
     *         specified element
     * @throws ClassCastException if {@code e} cannot be compared
     *         with the elements currently in this set
     * @throws NullPointerException if the specified element is null
     */
    public boolean add(E e) {
        return m.putIfAbsent(e, Boolean.TRUE) == null;
    }

    /**
     * Removes the specified element from this set if it is present.
     * More formally, removes an element {@code e} such that
     * {@code o.equals(e)}, if this set contains such an element.
     * Returns {@code true} if this set contained the element (or
     * equivalently, if this set changed as a result of the call).
     * (This set will not contain the element once the call returns.)
     *
     * @param o object to be removed from this set, if present
     * @return {@code true} if this set contained the specified element
     * @throws ClassCastException if {@code o} cannot be compared
     *         with the elements currently in this set
     * @throws NullPointerException if the specified element is null
     */
    public boolean remove(Object o) {
        return m.remove(o, Boolean.TRUE);
    }

    /**
     * Removes all of the elements from this set.
     */
    public void clear() {
        m.clear();
    }

    /**
     * Returns an iterator over the elements in this set in ascending order.
     *
     * @return an iterator over the elements in this set in ascending order
     */
    public Iterator<E> iterator() {
        return m.navigableKeySet().iterator();
    }

    /**
     * Returns an iterator over the elements in this set in descending order.
     *
     * @return an iterator over the elements in this set in descending order
     */
    public Iterator<E> descendingIterator() {
        return m.descendingKeySet().iterator();
    }


    /* ---------------- AbstractSet Overrides -------------- */

    /**
     * Compares the specified object with this set for equality.  Returns
     * {@code true} if the specified object is also a set, the two sets
     * have the same size, and every member of the specified set is
     * contained in this set (or equivalently, every member of this set is
     * contained in the specified set).  This definition ensures that the
     * equals method works properly across different implementations of the
     * set interface.
     *
     * @param o the object to be compared for equality with this set
     * @return {@code true} if the specified object is equal to this set
     */
    public boolean equals(Object o) {
        // Override AbstractSet version to avoid calling size()
        if (o == this)
            return true;
        if (!(o instanceof Set))
            return false;
        Collection<?> c = (Collection<?>) o;
        try {
            return containsAll(c) && c.containsAll(this);
        } catch (ClassCastException unused) {
            return false;
        } catch (NullPointerException unused) {
            return false;
        }
    }

    /**
     * Removes from this set all of its elements that are contained in
     * the specified collection.  If the specified collection is also
     * a set, this operation effectively modifies this set so that its
     * value is the <i>asymmetric set difference</i> of the two sets.
     *
     * @param  c collection containing elements to be removed from this set
     * @return {@code true} if this set changed as a result of the call
     * @throws ClassCastException if the types of one or more elements in this
     *         set are incompatible with the specified collection
     * @throws NullPointerException if the specified collection or any
     *         of its elements are null
     */
    public boolean removeAll(Collection<?> c) {
        // Override AbstractSet version to avoid unnecessary call to size()
        boolean modified = false;
        for (Object e : c)
            if (remove(e))
                modified = true;
        return modified;
    }

    /* ---------------- Relational operations -------------- */

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if the specified element is null
     */
    public E lower(E e) {
        return m.lowerKey(e);
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if the specified element is null
     */
    public E floor(E e) {
        return m.floorKey(e);
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if the specified element is null
     */
    public E ceiling(E e) {
        return m.ceilingKey(e);
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if the specified element is null
     */
    public E higher(E e) {
        return m.higherKey(e);
    }

    public E pollFirst() {
        Map.Entry<E,Object> e = m.pollFirstEntry();
        return (e == null) ? null : e.getKey();
    }

    public E pollLast() {
        Map.Entry<E,Object> e = m.pollLastEntry();
        return (e == null) ? null : e.getKey();
    }


    /* ---------------- SortedSet operations -------------- */


    public Comparator<? super E> comparator() {
        return m.comparator();
    }

    /**
     * @throws NoSuchElementException {@inheritDoc}
     */
    public E first() {
        return m.firstKey();
    }

    /**
     * @throws NoSuchElementException {@inheritDoc}
     */
    public E last() {
        return m.lastKey();
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code fromElement} or
     *         {@code toElement} is null
     * @throws IllegalArgumentException {@inheritDoc}
     */
    public NavigableSet<E> subSet(E fromElement,
                                  boolean fromInclusive,
                                  E toElement,
                                  boolean toInclusive) {
        return new ConcurrentSkipListSet<E>
            (m.subMap(fromElement, fromInclusive,
                      toElement,   toInclusive));
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code toElement} is null
     * @throws IllegalArgumentException {@inheritDoc}
     */
    public NavigableSet<E> headSet(E toElement, boolean inclusive) {
        return new ConcurrentSkipListSet<E>(m.headMap(toElement, inclusive));
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code fromElement} is null
     * @throws IllegalArgumentException {@inheritDoc}
     */
    public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
        return new ConcurrentSkipListSet<E>(m.tailMap(fromElement, inclusive));
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code fromElement} or
     *         {@code toElement} is null
     * @throws IllegalArgumentException {@inheritDoc}
     */
    public NavigableSet<E> subSet(E fromElement, E toElement) {
        return subSet(fromElement, true, toElement, false);
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code toElement} is null
     * @throws IllegalArgumentException {@inheritDoc}
     */
    public NavigableSet<E> headSet(E toElement) {
        return headSet(toElement, false);
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code fromElement} is null
     * @throws IllegalArgumentException {@inheritDoc}
     */
    public NavigableSet<E> tailSet(E fromElement) {
        return tailSet(fromElement, true);
    }

    /**
     * Returns a reverse order view of the elements contained in this set.
     * The descending set is backed by this set, so changes to the set are
     * reflected in the descending set, and vice-versa.
     *
     * <p>The returned set has an ordering equivalent to
     * <tt>{@link Collections#reverseOrder(Comparator) Collections.reverseOrder}(comparator())</tt>.
     * The expression {@code s.descendingSet().descendingSet()} returns a
     * view of {@code s} essentially equivalent to {@code s}.
     *
     * @return a reverse order view of this set
     */
    public NavigableSet<E> descendingSet() {
        return new ConcurrentSkipListSet<E>(m.descendingMap());
    }

    public Stream<E> stream() {
        int flags = Streams.STREAM_IS_DISTINCT |
            Streams.STREAM_IS_SORTED | Streams.STREAM_IS_ORDERED;
        int sizedFlags = flags | Streams.STREAM_IS_SIZED;
        if (m instanceof ConcurrentSkipListMap)
            return Streams.stream
                (() -> ((ConcurrentSkipListMap<E,?>)m).keySpliterator(),
                 sizedFlags);
        else
            return Streams.stream
                (Streams.spliteratorUnknownSize(iterator()), flags);
    }

    public Stream<E> parallelStream() {
        int flags = Streams.STREAM_IS_DISTINCT |
            Streams.STREAM_IS_SORTED | Streams.STREAM_IS_ORDERED;
        int sizedFlags = flags | Streams.STREAM_IS_SIZED;
        if (m instanceof ConcurrentSkipListMap)
            return Streams.parallelStream
                (() -> ((ConcurrentSkipListMap<E,?>)m).keySpliterator(),
                 sizedFlags);
        else
            return Streams.parallelStream
                (Streams.spliteratorUnknownSize(iterator()), flags);
    }

    // Support for resetting map in clone
    private void setMap(ConcurrentNavigableMap<E,Object> map) {
        UNSAFE.putObjectVolatile(this, mapOffset, map);
    }

    private static final sun.misc.Unsafe UNSAFE;
    private static final long mapOffset;
    static {
        try {
            UNSAFE = sun.misc.Unsafe.getUnsafe();
            Class<?> k = ConcurrentSkipListSet.class;
            mapOffset = UNSAFE.objectFieldOffset
                (k.getDeclaredField("m"));
        } catch (Exception e) {
            throw new Error(e);
        }
    }
}
Revision:	1.31
Committed:	Wed Jan 16 15:04:03 2013 UTC (11 years, 4 months ago) by dl
Branch:	MAIN
Changes since 1.30:	+29 -0 lines
Log Message:	lambda-lib support
#	User	Rev	Content
1	dl	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	jsr166	1.22	* http://creativecommons.org/publicdomain/zero/1.0/
5	dl	1.1	*/
6
7			package java.util.concurrent;
8			import java.util.*;
9	dl	1.31	import java.util.Spliterator;
10			import java.util.stream.Stream;
11			import java.util.stream.Streams;
12	dl	1.1
13			/**
14			* A scalable concurrent {@link NavigableSet} implementation based on
15	jsr166	1.11	* a {@link ConcurrentSkipListMap}. The elements of the set are kept
16			* sorted according to their {@linkplain Comparable natural ordering},
17			* or by a {@link Comparator} provided at set creation time, depending
18			* on which constructor is used.
19	dl	1.1	*
20	jsr166	1.11	* <p>This implementation provides expected average <i>log(n)</i> time
21	jsr166	1.30	* cost for the {@code contains}, {@code add}, and {@code remove}
22	dl	1.1	* operations and their variants. Insertion, removal, and access
23	jsr166	1.11	* operations safely execute concurrently by multiple threads.
24			* Iterators are <i>weakly consistent</i>, returning elements
25	dl	1.1	* reflecting the state of the set at some point at or since the
26			* creation of the iterator. They do <em>not</em> throw {@link
27	dl	1.2	* ConcurrentModificationException}, and may proceed concurrently with
28	jsr166	1.11	* other operations. Ascending ordered views and their iterators are
29			* faster than descending ones.
30	dl	1.1	*
31	jsr166	1.30	* <p>Beware that, unlike in most collections, the {@code size}
32	dl	1.1	* method is <em>not</em> a constant-time operation. Because of the
33			* asynchronous nature of these sets, determining the current number
34	dl	1.23	* of elements requires a traversal of the elements, and so may report
35			* inaccurate results if this collection is modified during traversal.
36	jsr166	1.30	* Additionally, the bulk operations {@code addAll},
37			* {@code removeAll}, {@code retainAll}, {@code containsAll},
38			* {@code equals}, and {@code toArray} are <em>not</em> guaranteed
39	dl	1.23	* to be performed atomically. For example, an iterator operating
40	jsr166	1.30	* concurrently with an {@code addAll} operation might view only some
41	dl	1.23	* of the added elements.
42	dl	1.1	*
43			* <p>This class and its iterators implement all of the
44			* <em>optional</em> methods of the {@link Set} and {@link Iterator}
45			* interfaces. Like most other concurrent collection implementations,
46	jsr166	1.30	* this class does not permit the use of {@code null} elements,
47			* because {@code null} arguments and return values cannot be reliably
48	dl	1.1	* distinguished from the absence of elements.
49			*
50	jsr166	1.10	* <p>This class is a member of the
51	jsr166	1.18	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
52	jsr166	1.10	* Java Collections Framework</a>.
53			*
54	dl	1.1	* @author Doug Lea
55			* @param <E> the type of elements maintained by this set
56	jsr166	1.9	* @since 1.6
57	dl	1.1	*/
58			public class ConcurrentSkipListSet<E>
59			extends AbstractSet<E>
60			implements NavigableSet<E>, Cloneable, java.io.Serializable {
61
62			private static final long serialVersionUID = -2479143111061671589L;
63
64			/**
65			* The underlying map. Uses Boolean.TRUE as value for each
66	dl	1.15	* element. This field is declared final for the sake of thread
67			* safety, which entails some ugliness in clone()
68	dl	1.1	*/
69	dl	1.15	private final ConcurrentNavigableMap<E,Object> m;
70	dl	1.1
71			/**
72	jsr166	1.11	* Constructs a new, empty set that orders its elements according to
73			* their {@linkplain Comparable natural ordering}.
74	dl	1.1	*/
75			public ConcurrentSkipListSet() {
76			m = new ConcurrentSkipListMap<E,Object>();
77			}
78
79			/**
80	jsr166	1.11	* Constructs a new, empty set that orders its elements according to
81			* the specified comparator.
82	dl	1.1	*
83	jsr166	1.11	* @param comparator the comparator that will be used to order this set.
84	jsr166	1.30	* If {@code null}, the {@linkplain Comparable natural
85	jsr166	1.11	* ordering} of the elements will be used.
86	dl	1.1	*/
87	jsr166	1.11	public ConcurrentSkipListSet(Comparator<? super E> comparator) {
88			m = new ConcurrentSkipListMap<E,Object>(comparator);
89	dl	1.1	}
90
91			/**
92			* Constructs a new set containing the elements in the specified
93	jsr166	1.11	* collection, that orders its elements according to their
94			* {@linkplain Comparable natural ordering}.
95	dl	1.1	*
96	jsr166	1.11	* @param c The elements that will comprise the new set
97	jsr166	1.30	* @throws ClassCastException if the elements in {@code c} are
98	jsr166	1.11	* not {@link Comparable}, or are not mutually comparable
99			* @throws NullPointerException if the specified collection or any
100			* of its elements are null
101	dl	1.1	*/
102			public ConcurrentSkipListSet(Collection<? extends E> c) {
103			m = new ConcurrentSkipListMap<E,Object>();
104			addAll(c);
105			}
106
107			/**
108	jsr166	1.11	* Constructs a new set containing the same elements and using the
109			* same ordering as the specified sorted set.
110	dl	1.1	*
111	jsr166	1.11	* @param s sorted set whose elements will comprise the new set
112			* @throws NullPointerException if the specified sorted set or any
113			* of its elements are null
114	dl	1.1	*/
115			public ConcurrentSkipListSet(SortedSet<E> s) {
116			m = new ConcurrentSkipListMap<E,Object>(s.comparator());
117			addAll(s);
118			}
119
120			/**
121	dl	1.15	* For use by submaps
122			*/
123			ConcurrentSkipListSet(ConcurrentNavigableMap<E,Object> m) {
124			this.m = m;
125			}
126
127			/**
128	jsr166	1.30	* Returns a shallow copy of this {@code ConcurrentSkipListSet}
129	jsr166	1.11	* instance. (The elements themselves are not cloned.)
130	dl	1.1	*
131	jsr166	1.11	* @return a shallow copy of this set
132	dl	1.1	*/
133	jsr166	1.7	public ConcurrentSkipListSet<E> clone() {
134	jsr166	1.19	try {
135	jsr166	1.28	@SuppressWarnings("unchecked")
136			ConcurrentSkipListSet<E> clone =
137			(ConcurrentSkipListSet<E>) super.clone();
138	jsr166	1.24	clone.setMap(new ConcurrentSkipListMap<E,Object>(m));
139	jsr166	1.28	return clone;
140	jsr166	1.19	} catch (CloneNotSupportedException e) {
141			throw new InternalError();
142			}
143	dl	1.1	}
144
145			/* ---------------- Set operations -------------- */
146
147			/**
148			* Returns the number of elements in this set. If this set
149	jsr166	1.30	* contains more than {@code Integer.MAX_VALUE} elements, it
150			* returns {@code Integer.MAX_VALUE}.
151	dl	1.1	*
152			* <p>Beware that, unlike in most collections, this method is
153			* <em>NOT</em> a constant-time operation. Because of the
154			* asynchronous nature of these sets, determining the current
155			* number of elements requires traversing them all to count them.
156			* Additionally, it is possible for the size to change during
157			* execution of this method, in which case the returned result
158			* will be inaccurate. Thus, this method is typically not very
159			* useful in concurrent applications.
160			*
161	jsr166	1.12	* @return the number of elements in this set
162	dl	1.1	*/
163			public int size() {
164	jsr166	1.19	return m.size();
165	dl	1.1	}
166
167			/**
168	jsr166	1.30	* Returns {@code true} if this set contains no elements.
169			* @return {@code true} if this set contains no elements
170	dl	1.1	*/
171			public boolean isEmpty() {
172	jsr166	1.19	return m.isEmpty();
173	dl	1.1	}
174
175			/**
176	jsr166	1.30	* Returns {@code true} if this set contains the specified element.
177			* More formally, returns {@code true} if and only if this set
178			* contains an element {@code e} such that {@code o.equals(e)}.
179	dl	1.1	*
180	jsr166	1.14	* @param o object to be checked for containment in this set
181	jsr166	1.30	* @return {@code true} if this set contains the specified element
182	jsr166	1.11	* @throws ClassCastException if the specified element cannot be
183	jsr166	1.14	* compared with the elements currently in this set
184	jsr166	1.11	* @throws NullPointerException if the specified element is null
185	dl	1.1	*/
186			public boolean contains(Object o) {
187	jsr166	1.19	return m.containsKey(o);
188	dl	1.1	}
189
190			/**
191			* Adds the specified element to this set if it is not already present.
192	jsr166	1.30	* More formally, adds the specified element {@code e} to this set if
193			* the set contains no element {@code e2} such that {@code e.equals(e2)}.
194	jsr166	1.14	* If this set already contains the element, the call leaves the set
195	jsr166	1.30	* unchanged and returns {@code false}.
196	dl	1.1	*
197	jsr166	1.11	* @param e element to be added to this set
198	jsr166	1.30	* @return {@code true} if this set did not already contain the
199	jsr166	1.11	* specified element
200	jsr166	1.30	* @throws ClassCastException if {@code e} cannot be compared
201	jsr166	1.14	* with the elements currently in this set
202	jsr166	1.11	* @throws NullPointerException if the specified element is null
203	dl	1.1	*/
204	jsr166	1.5	public boolean add(E e) {
205	jsr166	1.19	return m.putIfAbsent(e, Boolean.TRUE) == null;
206	dl	1.1	}
207
208			/**
209			* Removes the specified element from this set if it is present.
210	jsr166	1.30	* More formally, removes an element {@code e} such that
211			* {@code o.equals(e)}, if this set contains such an element.
212			* Returns {@code true} if this set contained the element (or
213	jsr166	1.14	* equivalently, if this set changed as a result of the call).
214			* (This set will not contain the element once the call returns.)
215	dl	1.1	*
216	jsr166	1.11	* @param o object to be removed from this set, if present
217	jsr166	1.30	* @return {@code true} if this set contained the specified element
218			* @throws ClassCastException if {@code o} cannot be compared
219	jsr166	1.14	* with the elements currently in this set
220	jsr166	1.11	* @throws NullPointerException if the specified element is null
221	dl	1.1	*/
222			public boolean remove(Object o) {
223	jsr166	1.19	return m.remove(o, Boolean.TRUE);
224	dl	1.1	}
225
226			/**
227			* Removes all of the elements from this set.
228			*/
229			public void clear() {
230	jsr166	1.19	m.clear();
231	dl	1.1	}
232
233			/**
234	jsr166	1.11	* Returns an iterator over the elements in this set in ascending order.
235	dl	1.1	*
236	jsr166	1.11	* @return an iterator over the elements in this set in ascending order
237	dl	1.1	*/
238			public Iterator<E> iterator() {
239	dl	1.15	return m.navigableKeySet().iterator();
240	dl	1.1	}
241
242			/**
243	jsr166	1.11	* Returns an iterator over the elements in this set in descending order.
244	dl	1.1	*
245	jsr166	1.11	* @return an iterator over the elements in this set in descending order
246	dl	1.1	*/
247			public Iterator<E> descendingIterator() {
248	jsr166	1.19	return m.descendingKeySet().iterator();
249	dl	1.1	}
250
251	dl	1.15
252	dl	1.1	/* ---------------- AbstractSet Overrides -------------- */
253
254			/**
255			* Compares the specified object with this set for equality. Returns
256	jsr166	1.30	* {@code true} if the specified object is also a set, the two sets
257	dl	1.1	* have the same size, and every member of the specified set is
258			* contained in this set (or equivalently, every member of this set is
259			* contained in the specified set). This definition ensures that the
260			* equals method works properly across different implementations of the
261			* set interface.
262			*
263	jsr166	1.11	* @param o the object to be compared for equality with this set
264	jsr166	1.30	* @return {@code true} if the specified object is equal to this set
265	dl	1.1	*/
266			public boolean equals(Object o) {
267			// Override AbstractSet version to avoid calling size()
268	jsr166	1.19	if (o == this)
269			return true;
270			if (!(o instanceof Set))
271			return false;
272			Collection<?> c = (Collection<?>) o;
273	dl	1.1	try {
274			return containsAll(c) && c.containsAll(this);
275	jsr166	1.29	} catch (ClassCastException unused) {
276	dl	1.1	return false;
277	jsr166	1.6	} catch (NullPointerException unused) {
278	dl	1.1	return false;
279			}
280			}
281	jsr166	1.8
282	dl	1.1	/**
283			* Removes from this set all of its elements that are contained in
284			* the specified collection. If the specified collection is also
285			* a set, this operation effectively modifies this set so that its
286			* value is the <i>asymmetric set difference</i> of the two sets.
287			*
288	jsr166	1.11	* @param c collection containing elements to be removed from this set
289	jsr166	1.30	* @return {@code true} if this set changed as a result of the call
290	dl	1.1	* @throws ClassCastException if the types of one or more elements in this
291	jsr166	1.11	* set are incompatible with the specified collection
292			* @throws NullPointerException if the specified collection or any
293			* of its elements are null
294	dl	1.1	*/
295			public boolean removeAll(Collection<?> c) {
296			// Override AbstractSet version to avoid unnecessary call to size()
297			boolean modified = false;
298	jsr166	1.27	for (Object e : c)
299			if (remove(e))
300	dl	1.1	modified = true;
301			return modified;
302			}
303	jsr166	1.8
304	dl	1.1	/* ---------------- Relational operations -------------- */
305
306			/**
307	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
308			* @throws NullPointerException if the specified element is null
309	dl	1.1	*/
310	jsr166	1.11	public E lower(E e) {
311			return m.lowerKey(e);
312	dl	1.1	}
313
314			/**
315	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
316			* @throws NullPointerException if the specified element is null
317	dl	1.1	*/
318	jsr166	1.11	public E floor(E e) {
319			return m.floorKey(e);
320	dl	1.1	}
321
322			/**
323	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
324			* @throws NullPointerException if the specified element is null
325	dl	1.1	*/
326	jsr166	1.11	public E ceiling(E e) {
327			return m.ceilingKey(e);
328	dl	1.1	}
329
330			/**
331	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
332			* @throws NullPointerException if the specified element is null
333	dl	1.1	*/
334	jsr166	1.5	public E higher(E e) {
335			return m.higherKey(e);
336	dl	1.1	}
337
338			public E pollFirst() {
339	dl	1.15	Map.Entry<E,Object> e = m.pollFirstEntry();
340	jsr166	1.20	return (e == null) ? null : e.getKey();
341	dl	1.1	}
342
343			public E pollLast() {
344	dl	1.15	Map.Entry<E,Object> e = m.pollLastEntry();
345	jsr166	1.20	return (e == null) ? null : e.getKey();
346	dl	1.1	}
347
348
349			/* ---------------- SortedSet operations -------------- */
350
351
352			public Comparator<? super E> comparator() {
353			return m.comparator();
354			}
355
356			/**
357	jsr166	1.11	* @throws NoSuchElementException {@inheritDoc}
358	dl	1.1	*/
359			public E first() {
360			return m.firstKey();
361			}
362
363			/**
364	jsr166	1.11	* @throws NoSuchElementException {@inheritDoc}
365	dl	1.1	*/
366			public E last() {
367			return m.lastKey();
368			}
369
370			/**
371	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
372	jsr166	1.17	* @throws NullPointerException if {@code fromElement} or
373			* {@code toElement} is null
374	jsr166	1.11	* @throws IllegalArgumentException {@inheritDoc}
375	dl	1.1	*/
376	dl	1.16	public NavigableSet<E> subSet(E fromElement,
377			boolean fromInclusive,
378			E toElement,
379			boolean toInclusive) {
380	jsr166	1.19	return new ConcurrentSkipListSet<E>
381	dl	1.16	(m.subMap(fromElement, fromInclusive,
382			toElement, toInclusive));
383	dl	1.1	}
384
385			/**
386	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
387	jsr166	1.17	* @throws NullPointerException if {@code toElement} is null
388	jsr166	1.11	* @throws IllegalArgumentException {@inheritDoc}
389	dl	1.1	*/
390	dl	1.16	public NavigableSet<E> headSet(E toElement, boolean inclusive) {
391	jsr166	1.19	return new ConcurrentSkipListSet<E>(m.headMap(toElement, inclusive));
392	dl	1.1	}
393
394			/**
395	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
396	jsr166	1.17	* @throws NullPointerException if {@code fromElement} is null
397	jsr166	1.11	* @throws IllegalArgumentException {@inheritDoc}
398	dl	1.1	*/
399	dl	1.16	public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
400	jsr166	1.19	return new ConcurrentSkipListSet<E>(m.tailMap(fromElement, inclusive));
401	dl	1.3	}
402
403			/**
404	jsr166	1.17	* @throws ClassCastException {@inheritDoc}
405			* @throws NullPointerException if {@code fromElement} or
406			* {@code toElement} is null
407	jsr166	1.11	* @throws IllegalArgumentException {@inheritDoc}
408	dl	1.3	*/
409	jsr166	1.18	public NavigableSet<E> subSet(E fromElement, E toElement) {
410	jsr166	1.19	return subSet(fromElement, true, toElement, false);
411	dl	1.3	}
412
413			/**
414	jsr166	1.17	* @throws ClassCastException {@inheritDoc}
415			* @throws NullPointerException if {@code toElement} is null
416	jsr166	1.11	* @throws IllegalArgumentException {@inheritDoc}
417	dl	1.3	*/
418	jsr166	1.18	public NavigableSet<E> headSet(E toElement) {
419	jsr166	1.19	return headSet(toElement, false);
420	dl	1.3	}
421
422			/**
423	jsr166	1.17	* @throws ClassCastException {@inheritDoc}
424			* @throws NullPointerException if {@code fromElement} is null
425	jsr166	1.11	* @throws IllegalArgumentException {@inheritDoc}
426	dl	1.3	*/
427	jsr166	1.18	public NavigableSet<E> tailSet(E fromElement) {
428	jsr166	1.19	return tailSet(fromElement, true);
429	dl	1.1	}
430
431			/**
432	jsr166	1.18	* Returns a reverse order view of the elements contained in this set.
433			* The descending set is backed by this set, so changes to the set are
434			* reflected in the descending set, and vice-versa.
435			*
436			* <p>The returned set has an ordering equivalent to
437			* <tt>{@link Collections#reverseOrder(Comparator) Collections.reverseOrder}(comparator())</tt>.
438			* The expression {@code s.descendingSet().descendingSet()} returns a
439			* view of {@code s} essentially equivalent to {@code s}.
440			*
441			* @return a reverse order view of this set
442	dl	1.15	*/
443			public NavigableSet<E> descendingSet() {
444	jsr166	1.24	return new ConcurrentSkipListSet<E>(m.descendingMap());
445	dl	1.15	}
446	dl	1.1
447	dl	1.31	public Stream<E> stream() {
448			int flags = Streams.STREAM_IS_DISTINCT \|
449			Streams.STREAM_IS_SORTED \| Streams.STREAM_IS_ORDERED;
450			int sizedFlags = flags \| Streams.STREAM_IS_SIZED;
451			if (m instanceof ConcurrentSkipListMap)
452			return Streams.stream
453			(() -> ((ConcurrentSkipListMap<E,?>)m).keySpliterator(),
454			sizedFlags);
455			else
456			return Streams.stream
457			(Streams.spliteratorUnknownSize(iterator()), flags);
458			}
459
460			public Stream<E> parallelStream() {
461			int flags = Streams.STREAM_IS_DISTINCT \|
462			Streams.STREAM_IS_SORTED \| Streams.STREAM_IS_ORDERED;
463			int sizedFlags = flags \| Streams.STREAM_IS_SIZED;
464			if (m instanceof ConcurrentSkipListMap)
465			return Streams.parallelStream
466			(() -> ((ConcurrentSkipListMap<E,?>)m).keySpliterator(),
467			sizedFlags);
468			else
469			return Streams.parallelStream
470			(Streams.spliteratorUnknownSize(iterator()), flags);
471			}
472
473	dl	1.15	// Support for resetting map in clone
474	dl	1.21	private void setMap(ConcurrentNavigableMap<E,Object> map) {
475			UNSAFE.putObjectVolatile(this, mapOffset, map);
476			}
477
478			private static final sun.misc.Unsafe UNSAFE;
479	dl	1.15	private static final long mapOffset;
480			static {
481			try {
482	dl	1.21	UNSAFE = sun.misc.Unsafe.getUnsafe();
483	jsr166	1.24	Class<?> k = ConcurrentSkipListSet.class;
484	dl	1.21	mapOffset = UNSAFE.objectFieldOffset
485			(k.getDeclaredField("m"));
486			} catch (Exception e) {
487			throw new Error(e);
488			}
489	dl	1.15	}
490	jsr166	1.8	}