author | dl |
Mon, 12 Dec 2011 10:45:54 +0000 | |
changeset 11279 | d9dab5ec5044 |
parent 9515 | 04056ec0f477 |
child 14325 | 622c473a21aa |
permissions | -rw-r--r-- |
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/* |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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/* |
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* This file is available under and governed by the GNU General Public |
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* License version 2 only, as published by the Free Software Foundation. |
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* However, the following notice accompanied the original version of this |
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* file: |
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* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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package java.util.concurrent; |
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import java.util.*; |
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/** |
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* A scalable concurrent {@link NavigableSet} implementation based on |
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* a {@link ConcurrentSkipListMap}. The elements of the set are kept |
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* sorted according to their {@linkplain Comparable natural ordering}, |
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* or by a {@link Comparator} provided at set creation time, depending |
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* on which constructor is used. |
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* |
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* <p>This implementation provides expected average <i>log(n)</i> time |
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* cost for the <tt>contains</tt>, <tt>add</tt>, and <tt>remove</tt> |
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* operations and their variants. Insertion, removal, and access |
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* operations safely execute concurrently by multiple threads. |
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* Iterators are <i>weakly consistent</i>, returning elements |
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* reflecting the state of the set at some point at or since the |
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* creation of the iterator. They do <em>not</em> throw {@link |
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* ConcurrentModificationException}, and may proceed concurrently with |
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* other operations. Ascending ordered views and their iterators are |
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* faster than descending ones. |
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* |
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* <p>Beware that, unlike in most collections, the <tt>size</tt> |
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* method is <em>not</em> a constant-time operation. Because of the |
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* asynchronous nature of these sets, determining the current number |
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* of elements requires a traversal of the elements, and so may report |
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* inaccurate results if this collection is modified during traversal. |
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* Additionally, the bulk operations <tt>addAll</tt>, |
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* <tt>removeAll</tt>, <tt>retainAll</tt>, <tt>containsAll</tt>, |
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* <tt>equals</tt>, and <tt>toArray</tt> are <em>not</em> guaranteed |
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* to be performed atomically. For example, an iterator operating |
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* concurrently with an <tt>addAll</tt> operation might view only some |
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* of the added elements. |
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* |
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* <p>This class and its iterators implement all of the |
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* <em>optional</em> methods of the {@link Set} and {@link Iterator} |
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* interfaces. Like most other concurrent collection implementations, |
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* this class does not permit the use of <tt>null</tt> elements, |
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* because <tt>null</tt> arguments and return values cannot be reliably |
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* distinguished from the absence of elements. |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @author Doug Lea |
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* @param <E> the type of elements maintained by this set |
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* @since 1.6 |
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*/ |
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public class ConcurrentSkipListSet<E> |
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extends AbstractSet<E> |
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implements NavigableSet<E>, Cloneable, java.io.Serializable { |
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private static final long serialVersionUID = -2479143111061671589L; |
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/** |
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* The underlying map. Uses Boolean.TRUE as value for each |
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* element. This field is declared final for the sake of thread |
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* safety, which entails some ugliness in clone() |
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*/ |
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private final ConcurrentNavigableMap<E,Object> m; |
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/** |
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* Constructs a new, empty set that orders its elements according to |
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* their {@linkplain Comparable natural ordering}. |
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*/ |
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public ConcurrentSkipListSet() { |
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m = new ConcurrentSkipListMap<E,Object>(); |
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} |
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/** |
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* Constructs a new, empty set that orders its elements according to |
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* the specified comparator. |
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* |
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* @param comparator the comparator that will be used to order this set. |
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* If <tt>null</tt>, the {@linkplain Comparable natural |
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* ordering} of the elements will be used. |
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*/ |
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public ConcurrentSkipListSet(Comparator<? super E> comparator) { |
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m = new ConcurrentSkipListMap<E,Object>(comparator); |
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} |
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/** |
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* Constructs a new set containing the elements in the specified |
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* collection, that orders its elements according to their |
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* {@linkplain Comparable natural ordering}. |
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* |
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* @param c The elements that will comprise the new set |
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* @throws ClassCastException if the elements in <tt>c</tt> are |
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* not {@link Comparable}, or are not mutually comparable |
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* @throws NullPointerException if the specified collection or any |
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* of its elements are null |
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*/ |
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public ConcurrentSkipListSet(Collection<? extends E> c) { |
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m = new ConcurrentSkipListMap<E,Object>(); |
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addAll(c); |
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} |
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/** |
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* Constructs a new set containing the same elements and using the |
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* same ordering as the specified sorted set. |
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* |
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* @param s sorted set whose elements will comprise the new set |
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* @throws NullPointerException if the specified sorted set or any |
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* of its elements are null |
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*/ |
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public ConcurrentSkipListSet(SortedSet<E> s) { |
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m = new ConcurrentSkipListMap<E,Object>(s.comparator()); |
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addAll(s); |
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} |
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/** |
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* For use by submaps |
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*/ |
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ConcurrentSkipListSet(ConcurrentNavigableMap<E,Object> m) { |
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this.m = m; |
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} |
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/** |
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* Returns a shallow copy of this <tt>ConcurrentSkipListSet</tt> |
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* instance. (The elements themselves are not cloned.) |
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* |
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* @return a shallow copy of this set |
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*/ |
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public ConcurrentSkipListSet<E> clone() { |
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try { |
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@SuppressWarnings("unchecked") |
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ConcurrentSkipListSet<E> clone = |
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(ConcurrentSkipListSet<E>) super.clone(); |
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clone.setMap(new ConcurrentSkipListMap<E,Object>(m)); |
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return clone; |
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} catch (CloneNotSupportedException e) { |
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throw new InternalError(); |
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} |
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} |
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/* ---------------- Set operations -------------- */ |
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/** |
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* Returns the number of elements in this set. If this set |
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* contains more than <tt>Integer.MAX_VALUE</tt> elements, it |
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* returns <tt>Integer.MAX_VALUE</tt>. |
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* |
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* <p>Beware that, unlike in most collections, this method is |
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* <em>NOT</em> a constant-time operation. Because of the |
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* asynchronous nature of these sets, determining the current |
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* number of elements requires traversing them all to count them. |
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* Additionally, it is possible for the size to change during |
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* execution of this method, in which case the returned result |
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* will be inaccurate. Thus, this method is typically not very |
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* useful in concurrent applications. |
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* |
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* @return the number of elements in this set |
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*/ |
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public int size() { |
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return m.size(); |
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} |
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/** |
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* Returns <tt>true</tt> if this set contains no elements. |
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* @return <tt>true</tt> if this set contains no elements |
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*/ |
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public boolean isEmpty() { |
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return m.isEmpty(); |
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} |
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/** |
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* Returns <tt>true</tt> if this set contains the specified element. |
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* More formally, returns <tt>true</tt> if and only if this set |
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* contains an element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
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* |
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* @param o object to be checked for containment in this set |
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* @return <tt>true</tt> if this set contains the specified element |
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* @throws ClassCastException if the specified element cannot be |
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* compared with the elements currently in this set |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public boolean contains(Object o) { |
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return m.containsKey(o); |
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} |
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/** |
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* Adds the specified element to this set if it is not already present. |
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* More formally, adds the specified element <tt>e</tt> to this set if |
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* the set contains no element <tt>e2</tt> such that <tt>e.equals(e2)</tt>. |
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* If this set already contains the element, the call leaves the set |
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* unchanged and returns <tt>false</tt>. |
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* |
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* @param e element to be added to this set |
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* @return <tt>true</tt> if this set did not already contain the |
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* specified element |
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* @throws ClassCastException if <tt>e</tt> cannot be compared |
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* with the elements currently in this set |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public boolean add(E e) { |
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return m.putIfAbsent(e, Boolean.TRUE) == null; |
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} |
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/** |
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* Removes the specified element from this set if it is present. |
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* More formally, removes an element <tt>e</tt> such that |
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* <tt>o.equals(e)</tt>, if this set contains such an element. |
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* Returns <tt>true</tt> if this set contained the element (or |
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* equivalently, if this set changed as a result of the call). |
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* (This set will not contain the element once the call returns.) |
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* |
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* @param o object to be removed from this set, if present |
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* @return <tt>true</tt> if this set contained the specified element |
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* @throws ClassCastException if <tt>o</tt> cannot be compared |
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* with the elements currently in this set |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public boolean remove(Object o) { |
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return m.remove(o, Boolean.TRUE); |
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} |
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/** |
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* Removes all of the elements from this set. |
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*/ |
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public void clear() { |
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m.clear(); |
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} |
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/** |
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* Returns an iterator over the elements in this set in ascending order. |
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* |
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* @return an iterator over the elements in this set in ascending order |
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*/ |
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public Iterator<E> iterator() { |
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return m.navigableKeySet().iterator(); |
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} |
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/** |
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* Returns an iterator over the elements in this set in descending order. |
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* |
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* @return an iterator over the elements in this set in descending order |
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*/ |
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public Iterator<E> descendingIterator() { |
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return m.descendingKeySet().iterator(); |
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} |
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277 |
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/* ---------------- AbstractSet Overrides -------------- */ |
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279 |
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280 |
/** |
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281 |
* Compares the specified object with this set for equality. Returns |
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282 |
* <tt>true</tt> if the specified object is also a set, the two sets |
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283 |
* have the same size, and every member of the specified set is |
|
284 |
* contained in this set (or equivalently, every member of this set is |
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* contained in the specified set). This definition ensures that the |
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* equals method works properly across different implementations of the |
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* set interface. |
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* |
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* @param o the object to be compared for equality with this set |
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* @return <tt>true</tt> if the specified object is equal to this set |
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291 |
*/ |
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292 |
public boolean equals(Object o) { |
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293 |
// Override AbstractSet version to avoid calling size() |
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294 |
if (o == this) |
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return true; |
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296 |
if (!(o instanceof Set)) |
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297 |
return false; |
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298 |
Collection<?> c = (Collection<?>) o; |
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299 |
try { |
|
300 |
return containsAll(c) && c.containsAll(this); |
|
301 |
} catch (ClassCastException unused) { |
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302 |
return false; |
|
303 |
} catch (NullPointerException unused) { |
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304 |
return false; |
|
305 |
} |
|
306 |
} |
|
307 |
||
308 |
/** |
|
309 |
* Removes from this set all of its elements that are contained in |
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310 |
* the specified collection. If the specified collection is also |
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311 |
* a set, this operation effectively modifies this set so that its |
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312 |
* value is the <i>asymmetric set difference</i> of the two sets. |
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313 |
* |
|
314 |
* @param c collection containing elements to be removed from this set |
|
315 |
* @return <tt>true</tt> if this set changed as a result of the call |
|
316 |
* @throws ClassCastException if the types of one or more elements in this |
|
317 |
* set are incompatible with the specified collection |
|
318 |
* @throws NullPointerException if the specified collection or any |
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319 |
* of its elements are null |
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320 |
*/ |
|
321 |
public boolean removeAll(Collection<?> c) { |
|
322 |
// Override AbstractSet version to avoid unnecessary call to size() |
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323 |
boolean modified = false; |
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11279 | 324 |
for (Object e : c) |
325 |
if (remove(e)) |
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2 | 326 |
modified = true; |
327 |
return modified; |
|
328 |
} |
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329 |
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330 |
/* ---------------- Relational operations -------------- */ |
|
331 |
||
332 |
/** |
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333 |
* @throws ClassCastException {@inheritDoc} |
|
334 |
* @throws NullPointerException if the specified element is null |
|
335 |
*/ |
|
336 |
public E lower(E e) { |
|
337 |
return m.lowerKey(e); |
|
338 |
} |
|
339 |
||
340 |
/** |
|
341 |
* @throws ClassCastException {@inheritDoc} |
|
342 |
* @throws NullPointerException if the specified element is null |
|
343 |
*/ |
|
344 |
public E floor(E e) { |
|
345 |
return m.floorKey(e); |
|
346 |
} |
|
347 |
||
348 |
/** |
|
349 |
* @throws ClassCastException {@inheritDoc} |
|
350 |
* @throws NullPointerException if the specified element is null |
|
351 |
*/ |
|
352 |
public E ceiling(E e) { |
|
353 |
return m.ceilingKey(e); |
|
354 |
} |
|
355 |
||
356 |
/** |
|
357 |
* @throws ClassCastException {@inheritDoc} |
|
358 |
* @throws NullPointerException if the specified element is null |
|
359 |
*/ |
|
360 |
public E higher(E e) { |
|
361 |
return m.higherKey(e); |
|
362 |
} |
|
363 |
||
364 |
public E pollFirst() { |
|
365 |
Map.Entry<E,Object> e = m.pollFirstEntry(); |
|
7518 | 366 |
return (e == null) ? null : e.getKey(); |
2 | 367 |
} |
368 |
||
369 |
public E pollLast() { |
|
370 |
Map.Entry<E,Object> e = m.pollLastEntry(); |
|
7518 | 371 |
return (e == null) ? null : e.getKey(); |
2 | 372 |
} |
373 |
||
374 |
||
375 |
/* ---------------- SortedSet operations -------------- */ |
|
376 |
||
377 |
||
378 |
public Comparator<? super E> comparator() { |
|
379 |
return m.comparator(); |
|
380 |
} |
|
381 |
||
382 |
/** |
|
383 |
* @throws NoSuchElementException {@inheritDoc} |
|
384 |
*/ |
|
385 |
public E first() { |
|
386 |
return m.firstKey(); |
|
387 |
} |
|
388 |
||
389 |
/** |
|
390 |
* @throws NoSuchElementException {@inheritDoc} |
|
391 |
*/ |
|
392 |
public E last() { |
|
393 |
return m.lastKey(); |
|
394 |
} |
|
395 |
||
396 |
/** |
|
397 |
* @throws ClassCastException {@inheritDoc} |
|
398 |
* @throws NullPointerException if {@code fromElement} or |
|
399 |
* {@code toElement} is null |
|
400 |
* @throws IllegalArgumentException {@inheritDoc} |
|
401 |
*/ |
|
402 |
public NavigableSet<E> subSet(E fromElement, |
|
403 |
boolean fromInclusive, |
|
404 |
E toElement, |
|
405 |
boolean toInclusive) { |
|
406 |
return new ConcurrentSkipListSet<E> |
|
407 |
(m.subMap(fromElement, fromInclusive, |
|
408 |
toElement, toInclusive)); |
|
409 |
} |
|
410 |
||
411 |
/** |
|
412 |
* @throws ClassCastException {@inheritDoc} |
|
413 |
* @throws NullPointerException if {@code toElement} is null |
|
414 |
* @throws IllegalArgumentException {@inheritDoc} |
|
415 |
*/ |
|
416 |
public NavigableSet<E> headSet(E toElement, boolean inclusive) { |
|
417 |
return new ConcurrentSkipListSet<E>(m.headMap(toElement, inclusive)); |
|
418 |
} |
|
419 |
||
420 |
/** |
|
421 |
* @throws ClassCastException {@inheritDoc} |
|
422 |
* @throws NullPointerException if {@code fromElement} is null |
|
423 |
* @throws IllegalArgumentException {@inheritDoc} |
|
424 |
*/ |
|
425 |
public NavigableSet<E> tailSet(E fromElement, boolean inclusive) { |
|
426 |
return new ConcurrentSkipListSet<E>(m.tailMap(fromElement, inclusive)); |
|
427 |
} |
|
428 |
||
429 |
/** |
|
430 |
* @throws ClassCastException {@inheritDoc} |
|
431 |
* @throws NullPointerException if {@code fromElement} or |
|
432 |
* {@code toElement} is null |
|
433 |
* @throws IllegalArgumentException {@inheritDoc} |
|
434 |
*/ |
|
435 |
public NavigableSet<E> subSet(E fromElement, E toElement) { |
|
436 |
return subSet(fromElement, true, toElement, false); |
|
437 |
} |
|
438 |
||
439 |
/** |
|
440 |
* @throws ClassCastException {@inheritDoc} |
|
441 |
* @throws NullPointerException if {@code toElement} is null |
|
442 |
* @throws IllegalArgumentException {@inheritDoc} |
|
443 |
*/ |
|
444 |
public NavigableSet<E> headSet(E toElement) { |
|
445 |
return headSet(toElement, false); |
|
446 |
} |
|
447 |
||
448 |
/** |
|
449 |
* @throws ClassCastException {@inheritDoc} |
|
450 |
* @throws NullPointerException if {@code fromElement} is null |
|
451 |
* @throws IllegalArgumentException {@inheritDoc} |
|
452 |
*/ |
|
453 |
public NavigableSet<E> tailSet(E fromElement) { |
|
454 |
return tailSet(fromElement, true); |
|
455 |
} |
|
456 |
||
457 |
/** |
|
458 |
* Returns a reverse order view of the elements contained in this set. |
|
459 |
* The descending set is backed by this set, so changes to the set are |
|
460 |
* reflected in the descending set, and vice-versa. |
|
461 |
* |
|
462 |
* <p>The returned set has an ordering equivalent to |
|
463 |
* <tt>{@link Collections#reverseOrder(Comparator) Collections.reverseOrder}(comparator())</tt>. |
|
464 |
* The expression {@code s.descendingSet().descendingSet()} returns a |
|
465 |
* view of {@code s} essentially equivalent to {@code s}. |
|
466 |
* |
|
467 |
* @return a reverse order view of this set |
|
468 |
*/ |
|
469 |
public NavigableSet<E> descendingSet() { |
|
11279 | 470 |
return new ConcurrentSkipListSet<E>(m.descendingMap()); |
2 | 471 |
} |
472 |
||
473 |
// Support for resetting map in clone |
|
8544
225896f7b33c
7017493: ConcurrentLinkedDeque: Unexpected initialization order can lead to crash due to use of Unsafe
dl
parents:
7518
diff
changeset
|
474 |
private void setMap(ConcurrentNavigableMap<E,Object> map) { |
225896f7b33c
7017493: ConcurrentLinkedDeque: Unexpected initialization order can lead to crash due to use of Unsafe
dl
parents:
7518
diff
changeset
|
475 |
UNSAFE.putObjectVolatile(this, mapOffset, map); |
225896f7b33c
7017493: ConcurrentLinkedDeque: Unexpected initialization order can lead to crash due to use of Unsafe
dl
parents:
7518
diff
changeset
|
476 |
} |
225896f7b33c
7017493: ConcurrentLinkedDeque: Unexpected initialization order can lead to crash due to use of Unsafe
dl
parents:
7518
diff
changeset
|
477 |
|
225896f7b33c
7017493: ConcurrentLinkedDeque: Unexpected initialization order can lead to crash due to use of Unsafe
dl
parents:
7518
diff
changeset
|
478 |
private static final sun.misc.Unsafe UNSAFE; |
2 | 479 |
private static final long mapOffset; |
480 |
static { |
|
481 |
try { |
|
8544
225896f7b33c
7017493: ConcurrentLinkedDeque: Unexpected initialization order can lead to crash due to use of Unsafe
dl
parents:
7518
diff
changeset
|
482 |
UNSAFE = sun.misc.Unsafe.getUnsafe(); |
11279 | 483 |
Class<?> k = ConcurrentSkipListSet.class; |
8544
225896f7b33c
7017493: ConcurrentLinkedDeque: Unexpected initialization order can lead to crash due to use of Unsafe
dl
parents:
7518
diff
changeset
|
484 |
mapOffset = UNSAFE.objectFieldOffset |
225896f7b33c
7017493: ConcurrentLinkedDeque: Unexpected initialization order can lead to crash due to use of Unsafe
dl
parents:
7518
diff
changeset
|
485 |
(k.getDeclaredField("m")); |
225896f7b33c
7017493: ConcurrentLinkedDeque: Unexpected initialization order can lead to crash due to use of Unsafe
dl
parents:
7518
diff
changeset
|
486 |
} catch (Exception e) { |
225896f7b33c
7017493: ConcurrentLinkedDeque: Unexpected initialization order can lead to crash due to use of Unsafe
dl
parents:
7518
diff
changeset
|
487 |
throw new Error(e); |
225896f7b33c
7017493: ConcurrentLinkedDeque: Unexpected initialization order can lead to crash due to use of Unsafe
dl
parents:
7518
diff
changeset
|
488 |
} |
2 | 489 |
} |
490 |
} |