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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. Adapted and released, under explicit permission, |
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* from JDK ArrayList.java which carries the following copyright: |
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* |
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* Copyright 1997 by Sun Microsystems, Inc., |
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* 901 San Antonio Road, Palo Alto, California, 94303, U.S.A. |
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* All rights reserved. |
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* |
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* This software is the confidential and proprietary information |
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* of Sun Microsystems, Inc. ("Confidential Information"). You |
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* shall not disclose such Confidential Information and shall use |
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* it only in accordance with the terms of the license agreement |
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* you entered into with Sun. |
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*/ |
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|
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package java.util.concurrent; |
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|
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import java.util.*; |
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import java.util.concurrent.locks.ReentrantLock; |
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|
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/** |
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* A thread-safe variant of {@link java.util.ArrayList} in which all mutative |
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* operations ({@code add}, {@code set}, and so on) are implemented by |
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* making a fresh copy of the underlying array. |
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* |
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* <p>This is ordinarily too costly, but may be <em>more</em> efficient |
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* than alternatives when traversal operations vastly outnumber |
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* mutations, and is useful when you cannot or don't want to |
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* synchronize traversals, yet need to preclude interference among |
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* concurrent threads. The "snapshot" style iterator method uses a |
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* reference to the state of the array at the point that the iterator |
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* was created. This array never changes during the lifetime of the |
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* iterator, so interference is impossible and the iterator is |
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* guaranteed not to throw {@code ConcurrentModificationException}. |
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* The iterator will not reflect additions, removals, or changes to |
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* the list since the iterator was created. Element-changing |
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* operations on iterators themselves ({@code remove}, {@code set}, and |
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* {@code add}) are not supported. These methods throw |
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* {@code UnsupportedOperationException}. |
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* |
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* <p>All elements are permitted, including {@code null}. |
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* |
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* <p>Memory consistency effects: As with other concurrent |
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* collections, actions in a thread prior to placing an object into a |
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* {@code CopyOnWriteArrayList} |
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* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> |
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* actions subsequent to the access or removal of that element from |
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* the {@code CopyOnWriteArrayList} in another thread. |
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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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* @since 1.5 |
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* @author Doug Lea |
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* @param <E> the type of elements held in this collection |
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*/ |
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public class CopyOnWriteArrayList<E> |
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implements List<E>, RandomAccess, Cloneable, java.io.Serializable { |
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private static final long serialVersionUID = 8673264195747942595L; |
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|
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/** The lock protecting all mutators */ |
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final transient ReentrantLock lock = new ReentrantLock(); |
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|
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/** The array, accessed only via getArray/setArray. */ |
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private transient volatile Object[] array; |
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|
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/** |
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* Gets the array. Non-private so as to also be accessible |
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* from CopyOnWriteArraySet class. |
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*/ |
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final Object[] getArray() { |
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return array; |
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} |
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|
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/** |
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* Sets the array. |
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*/ |
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final void setArray(Object[] a) { |
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array = a; |
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} |
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|
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/** |
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* Creates an empty list. |
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*/ |
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public CopyOnWriteArrayList() { |
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setArray(new Object[0]); |
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} |
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|
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/** |
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* Creates a list containing the elements of the specified |
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* collection, in the order they are returned by the collection's |
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* iterator. |
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* |
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* @param c the collection of initially held elements |
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* @throws NullPointerException if the specified collection is null |
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*/ |
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public CopyOnWriteArrayList(Collection<? extends E> c) { |
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Object[] elements = c.toArray(); |
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// c.toArray might (incorrectly) not return Object[] (see 6260652) |
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if (elements.getClass() != Object[].class) |
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elements = Arrays.copyOf(elements, elements.length, Object[].class); |
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setArray(elements); |
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} |
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|
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/** |
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* Creates a list holding a copy of the given array. |
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* |
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* @param toCopyIn the array (a copy of this array is used as the |
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* internal array) |
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* @throws NullPointerException if the specified array is null |
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*/ |
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public CopyOnWriteArrayList(E[] toCopyIn) { |
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setArray(Arrays.copyOf(toCopyIn, toCopyIn.length, Object[].class)); |
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} |
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|
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/** |
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* Returns the number of elements in this list. |
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* |
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* @return the number of elements in this list |
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*/ |
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public int size() { |
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return getArray().length; |
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} |
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|
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/** |
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* Returns {@code true} if this list contains no elements. |
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* |
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* @return {@code true} if this list contains no elements |
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*/ |
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public boolean isEmpty() { |
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return size() == 0; |
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} |
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|
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/** |
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* Tests for equality, coping with nulls. |
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*/ |
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private static boolean eq(Object o1, Object o2) { |
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return (o1 == null ? o2 == null : o1.equals(o2)); |
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} |
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|
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/** |
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* static version of indexOf, to allow repeated calls without |
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* needing to re-acquire array each time. |
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* @param o element to search for |
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* @param elements the array |
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* @param index first index to search |
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* @param fence one past last index to search |
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* @return index of element, or -1 if absent |
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*/ |
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private static int indexOf(Object o, Object[] elements, |
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int index, int fence) { |
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if (o == null) { |
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for (int i = index; i < fence; i++) |
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if (elements[i] == null) |
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return i; |
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} else { |
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for (int i = index; i < fence; i++) |
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if (o.equals(elements[i])) |
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return i; |
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} |
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return -1; |
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} |
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|
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/** |
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* static version of lastIndexOf. |
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* @param o element to search for |
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* @param elements the array |
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* @param index first index to search |
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* @return index of element, or -1 if absent |
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*/ |
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private static int lastIndexOf(Object o, Object[] elements, int index) { |
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if (o == null) { |
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for (int i = index; i >= 0; i--) |
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if (elements[i] == null) |
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return i; |
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} else { |
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for (int i = index; i >= 0; i--) |
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if (o.equals(elements[i])) |
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return i; |
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} |
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return -1; |
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} |
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|
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/** |
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* Returns {@code true} if this list contains the specified element. |
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* More formally, returns {@code true} if and only if this list contains |
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* at least one element {@code e} such that |
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* <tt>(o==null ? e==null : o.equals(e))</tt>. |
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* |
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* @param o element whose presence in this list is to be tested |
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* @return {@code true} if this list contains the specified element |
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*/ |
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public boolean contains(Object o) { |
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Object[] elements = getArray(); |
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return indexOf(o, elements, 0, elements.length) >= 0; |
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} |
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|
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/** |
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* {@inheritDoc} |
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*/ |
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public int indexOf(Object o) { |
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Object[] elements = getArray(); |
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return indexOf(o, elements, 0, elements.length); |
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} |
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|
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/** |
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* Returns the index of the first occurrence of the specified element in |
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* this list, searching forwards from {@code index}, or returns -1 if |
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* the element is not found. |
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* More formally, returns the lowest index {@code i} such that |
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* <tt>(i >= index && (e==null ? get(i)==null : e.equals(get(i))))</tt>, |
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* or -1 if there is no such index. |
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* |
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* @param e element to search for |
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* @param index index to start searching from |
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* @return the index of the first occurrence of the element in |
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* this list at position {@code index} or later in the list; |
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* {@code -1} if the element is not found. |
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* @throws IndexOutOfBoundsException if the specified index is negative |
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*/ |
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public int indexOf(E e, int index) { |
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Object[] elements = getArray(); |
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return indexOf(e, elements, index, elements.length); |
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} |
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|
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/** |
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* {@inheritDoc} |
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*/ |
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public int lastIndexOf(Object o) { |
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Object[] elements = getArray(); |
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return lastIndexOf(o, elements, elements.length - 1); |
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} |
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|
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/** |
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* Returns the index of the last occurrence of the specified element in |
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* this list, searching backwards from {@code index}, or returns -1 if |
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* the element is not found. |
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* More formally, returns the highest index {@code i} such that |
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* <tt>(i <= index && (e==null ? get(i)==null : e.equals(get(i))))</tt>, |
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* or -1 if there is no such index. |
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* |
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* @param e element to search for |
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* @param index index to start searching backwards from |
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* @return the index of the last occurrence of the element at position |
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* less than or equal to {@code index} in this list; |
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* -1 if the element is not found. |
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* @throws IndexOutOfBoundsException if the specified index is greater |
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* than or equal to the current size of this list |
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*/ |
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public int lastIndexOf(E e, int index) { |
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Object[] elements = getArray(); |
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return lastIndexOf(e, elements, index); |
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} |
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|
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/** |
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* Returns a shallow copy of this list. (The elements themselves |
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* are not copied.) |
260 |
* |
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* @return a clone of this list |
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*/ |
263 |
public Object clone() { |
264 |
try { |
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@SuppressWarnings("unchecked") |
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CopyOnWriteArrayList<E> clone = |
267 |
(CopyOnWriteArrayList<E>) super.clone(); |
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clone.resetLock(); |
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return clone; |
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} catch (CloneNotSupportedException e) { |
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// this shouldn't happen, since we are Cloneable |
272 |
throw new InternalError(); |
273 |
} |
274 |
} |
275 |
|
276 |
/** |
277 |
* Returns an array containing all of the elements in this list |
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* in proper sequence (from first to last element). |
279 |
* |
280 |
* <p>The returned array will be "safe" in that no references to it are |
281 |
* maintained by this list. (In other words, this method must allocate |
282 |
* a new array). The caller is thus free to modify the returned array. |
283 |
* |
284 |
* <p>This method acts as bridge between array-based and collection-based |
285 |
* APIs. |
286 |
* |
287 |
* @return an array containing all the elements in this list |
288 |
*/ |
289 |
public Object[] toArray() { |
290 |
Object[] elements = getArray(); |
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return Arrays.copyOf(elements, elements.length); |
292 |
} |
293 |
|
294 |
/** |
295 |
* Returns an array containing all of the elements in this list in |
296 |
* proper sequence (from first to last element); the runtime type of |
297 |
* the returned array is that of the specified array. If the list fits |
298 |
* in the specified array, it is returned therein. Otherwise, a new |
299 |
* array is allocated with the runtime type of the specified array and |
300 |
* the size of this list. |
301 |
* |
302 |
* <p>If this list fits in the specified array with room to spare |
303 |
* (i.e., the array has more elements than this list), the element in |
304 |
* the array immediately following the end of the list is set to |
305 |
* {@code null}. (This is useful in determining the length of this |
306 |
* list <i>only</i> if the caller knows that this list does not contain |
307 |
* any null elements.) |
308 |
* |
309 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
310 |
* array-based and collection-based APIs. Further, this method allows |
311 |
* precise control over the runtime type of the output array, and may, |
312 |
* under certain circumstances, be used to save allocation costs. |
313 |
* |
314 |
* <p>Suppose {@code x} is a list known to contain only strings. |
315 |
* The following code can be used to dump the list into a newly |
316 |
* allocated array of {@code String}: |
317 |
* |
318 |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
319 |
* |
320 |
* Note that {@code toArray(new Object[0])} is identical in function to |
321 |
* {@code toArray()}. |
322 |
* |
323 |
* @param a the array into which the elements of the list are to |
324 |
* be stored, if it is big enough; otherwise, a new array of the |
325 |
* same runtime type is allocated for this purpose. |
326 |
* @return an array containing all the elements in this list |
327 |
* @throws ArrayStoreException if the runtime type of the specified array |
328 |
* is not a supertype of the runtime type of every element in |
329 |
* this list |
330 |
* @throws NullPointerException if the specified array is null |
331 |
*/ |
332 |
@SuppressWarnings("unchecked") |
333 |
public <T> T[] toArray(T[] a) { |
334 |
Object[] elements = getArray(); |
335 |
int len = elements.length; |
336 |
if (a.length < len) |
337 |
return (T[]) Arrays.copyOf(elements, len, a.getClass()); |
338 |
else { |
339 |
System.arraycopy(elements, 0, a, 0, len); |
340 |
if (a.length > len) |
341 |
a[len] = null; |
342 |
return a; |
343 |
} |
344 |
} |
345 |
|
346 |
// Positional Access Operations |
347 |
|
348 |
@SuppressWarnings("unchecked") |
349 |
private E get(Object[] a, int index) { |
350 |
return (E) a[index]; |
351 |
} |
352 |
|
353 |
/** |
354 |
* {@inheritDoc} |
355 |
* |
356 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
357 |
*/ |
358 |
public E get(int index) { |
359 |
return get(getArray(), index); |
360 |
} |
361 |
|
362 |
/** |
363 |
* Replaces the element at the specified position in this list with the |
364 |
* specified element. |
365 |
* |
366 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
367 |
*/ |
368 |
public E set(int index, E element) { |
369 |
final ReentrantLock lock = this.lock; |
370 |
lock.lock(); |
371 |
try { |
372 |
Object[] elements = getArray(); |
373 |
E oldValue = get(elements, index); |
374 |
|
375 |
if (oldValue != element) { |
376 |
int len = elements.length; |
377 |
Object[] newElements = Arrays.copyOf(elements, len); |
378 |
newElements[index] = element; |
379 |
setArray(newElements); |
380 |
} else { |
381 |
// Not quite a no-op; ensures volatile write semantics |
382 |
setArray(elements); |
383 |
} |
384 |
return oldValue; |
385 |
} finally { |
386 |
lock.unlock(); |
387 |
} |
388 |
} |
389 |
|
390 |
/** |
391 |
* Appends the specified element to the end of this list. |
392 |
* |
393 |
* @param e element to be appended to this list |
394 |
* @return {@code true} (as specified by {@link Collection#add}) |
395 |
*/ |
396 |
public boolean add(E e) { |
397 |
final ReentrantLock lock = this.lock; |
398 |
lock.lock(); |
399 |
try { |
400 |
Object[] elements = getArray(); |
401 |
int len = elements.length; |
402 |
Object[] newElements = Arrays.copyOf(elements, len + 1); |
403 |
newElements[len] = e; |
404 |
setArray(newElements); |
405 |
return true; |
406 |
} finally { |
407 |
lock.unlock(); |
408 |
} |
409 |
} |
410 |
|
411 |
/** |
412 |
* Inserts the specified element at the specified position in this |
413 |
* list. Shifts the element currently at that position (if any) and |
414 |
* any subsequent elements to the right (adds one to their indices). |
415 |
* |
416 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
417 |
*/ |
418 |
public void add(int index, E element) { |
419 |
final ReentrantLock lock = this.lock; |
420 |
lock.lock(); |
421 |
try { |
422 |
Object[] elements = getArray(); |
423 |
int len = elements.length; |
424 |
if (index > len || index < 0) |
425 |
throw new IndexOutOfBoundsException("Index: "+index+ |
426 |
", Size: "+len); |
427 |
Object[] newElements; |
428 |
int numMoved = len - index; |
429 |
if (numMoved == 0) |
430 |
newElements = Arrays.copyOf(elements, len + 1); |
431 |
else { |
432 |
newElements = new Object[len + 1]; |
433 |
System.arraycopy(elements, 0, newElements, 0, index); |
434 |
System.arraycopy(elements, index, newElements, index + 1, |
435 |
numMoved); |
436 |
} |
437 |
newElements[index] = element; |
438 |
setArray(newElements); |
439 |
} finally { |
440 |
lock.unlock(); |
441 |
} |
442 |
} |
443 |
|
444 |
/** |
445 |
* Removes the element at the specified position in this list. |
446 |
* Shifts any subsequent elements to the left (subtracts one from their |
447 |
* indices). Returns the element that was removed from the list. |
448 |
* |
449 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
450 |
*/ |
451 |
public E remove(int index) { |
452 |
final ReentrantLock lock = this.lock; |
453 |
lock.lock(); |
454 |
try { |
455 |
Object[] elements = getArray(); |
456 |
int len = elements.length; |
457 |
E oldValue = get(elements, index); |
458 |
int numMoved = len - index - 1; |
459 |
if (numMoved == 0) |
460 |
setArray(Arrays.copyOf(elements, len - 1)); |
461 |
else { |
462 |
Object[] newElements = new Object[len - 1]; |
463 |
System.arraycopy(elements, 0, newElements, 0, index); |
464 |
System.arraycopy(elements, index + 1, newElements, index, |
465 |
numMoved); |
466 |
setArray(newElements); |
467 |
} |
468 |
return oldValue; |
469 |
} finally { |
470 |
lock.unlock(); |
471 |
} |
472 |
} |
473 |
|
474 |
/** |
475 |
* Removes the first occurrence of the specified element from this list, |
476 |
* if it is present. If this list does not contain the element, it is |
477 |
* unchanged. More formally, removes the element with the lowest index |
478 |
* {@code i} such that |
479 |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> |
480 |
* (if such an element exists). Returns {@code true} if this list |
481 |
* contained the specified element (or equivalently, if this list |
482 |
* changed as a result of the call). |
483 |
* |
484 |
* @param o element to be removed from this list, if present |
485 |
* @return {@code true} if this list contained the specified element |
486 |
*/ |
487 |
public boolean remove(Object o) { |
488 |
final ReentrantLock lock = this.lock; |
489 |
lock.lock(); |
490 |
try { |
491 |
Object[] elements = getArray(); |
492 |
int len = elements.length; |
493 |
if (len != 0) { |
494 |
// Copy while searching for element to remove |
495 |
// This wins in the normal case of element being present |
496 |
int newlen = len - 1; |
497 |
Object[] newElements = new Object[newlen]; |
498 |
|
499 |
for (int i = 0; i < newlen; ++i) { |
500 |
if (eq(o, elements[i])) { |
501 |
// found one; copy remaining and exit |
502 |
for (int k = i + 1; k < len; ++k) |
503 |
newElements[k-1] = elements[k]; |
504 |
setArray(newElements); |
505 |
return true; |
506 |
} else |
507 |
newElements[i] = elements[i]; |
508 |
} |
509 |
|
510 |
// special handling for last cell |
511 |
if (eq(o, elements[newlen])) { |
512 |
setArray(newElements); |
513 |
return true; |
514 |
} |
515 |
} |
516 |
return false; |
517 |
} finally { |
518 |
lock.unlock(); |
519 |
} |
520 |
} |
521 |
|
522 |
/** |
523 |
* Removes from this list all of the elements whose index is between |
524 |
* {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. |
525 |
* Shifts any succeeding elements to the left (reduces their index). |
526 |
* This call shortens the list by {@code (toIndex - fromIndex)} elements. |
527 |
* (If {@code toIndex==fromIndex}, this operation has no effect.) |
528 |
* |
529 |
* @param fromIndex index of first element to be removed |
530 |
* @param toIndex index after last element to be removed |
531 |
* @throws IndexOutOfBoundsException if fromIndex or toIndex out of range |
532 |
* ({@code fromIndex < 0 || toIndex > size() || toIndex < fromIndex}) |
533 |
*/ |
534 |
void removeRange(int fromIndex, int toIndex) { |
535 |
final ReentrantLock lock = this.lock; |
536 |
lock.lock(); |
537 |
try { |
538 |
Object[] elements = getArray(); |
539 |
int len = elements.length; |
540 |
|
541 |
if (fromIndex < 0 || toIndex > len || toIndex < fromIndex) |
542 |
throw new IndexOutOfBoundsException(); |
543 |
int newlen = len - (toIndex - fromIndex); |
544 |
int numMoved = len - toIndex; |
545 |
if (numMoved == 0) |
546 |
setArray(Arrays.copyOf(elements, newlen)); |
547 |
else { |
548 |
Object[] newElements = new Object[newlen]; |
549 |
System.arraycopy(elements, 0, newElements, 0, fromIndex); |
550 |
System.arraycopy(elements, toIndex, newElements, |
551 |
fromIndex, numMoved); |
552 |
setArray(newElements); |
553 |
} |
554 |
} finally { |
555 |
lock.unlock(); |
556 |
} |
557 |
} |
558 |
|
559 |
/** |
560 |
* Appends the element, if not present. |
561 |
* |
562 |
* @param e element to be added to this list, if absent |
563 |
* @return {@code true} if the element was added |
564 |
*/ |
565 |
public boolean addIfAbsent(E e) { |
566 |
final ReentrantLock lock = this.lock; |
567 |
lock.lock(); |
568 |
try { |
569 |
// Copy while checking if already present. |
570 |
// This wins in the most common case where it is not present |
571 |
Object[] elements = getArray(); |
572 |
int len = elements.length; |
573 |
Object[] newElements = new Object[len + 1]; |
574 |
for (int i = 0; i < len; ++i) { |
575 |
if (eq(e, elements[i])) |
576 |
return false; // exit, throwing away copy |
577 |
else |
578 |
newElements[i] = elements[i]; |
579 |
} |
580 |
newElements[len] = e; |
581 |
setArray(newElements); |
582 |
return true; |
583 |
} finally { |
584 |
lock.unlock(); |
585 |
} |
586 |
} |
587 |
|
588 |
/** |
589 |
* Returns {@code true} if this list contains all of the elements of the |
590 |
* specified collection. |
591 |
* |
592 |
* @param c collection to be checked for containment in this list |
593 |
* @return {@code true} if this list contains all of the elements of the |
594 |
* specified collection |
595 |
* @throws NullPointerException if the specified collection is null |
596 |
* @see #contains(Object) |
597 |
*/ |
598 |
public boolean containsAll(Collection<?> c) { |
599 |
Object[] elements = getArray(); |
600 |
int len = elements.length; |
601 |
for (Object e : c) { |
602 |
if (indexOf(e, elements, 0, len) < 0) |
603 |
return false; |
604 |
} |
605 |
return true; |
606 |
} |
607 |
|
608 |
/** |
609 |
* Removes from this list all of its elements that are contained in |
610 |
* the specified collection. This is a particularly expensive operation |
611 |
* in this class because of the need for an internal temporary array. |
612 |
* |
613 |
* @param c collection containing elements to be removed from this list |
614 |
* @return {@code true} if this list changed as a result of the call |
615 |
* @throws ClassCastException if the class of an element of this list |
616 |
* is incompatible with the specified collection |
617 |
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
618 |
* @throws NullPointerException if this list contains a null element and the |
619 |
* specified collection does not permit null elements |
620 |
* (<a href="../Collection.html#optional-restrictions">optional</a>), |
621 |
* or if the specified collection is null |
622 |
* @see #remove(Object) |
623 |
*/ |
624 |
public boolean removeAll(Collection<?> c) { |
625 |
if (c == null) throw new NullPointerException(); |
626 |
final ReentrantLock lock = this.lock; |
627 |
lock.lock(); |
628 |
try { |
629 |
Object[] elements = getArray(); |
630 |
int len = elements.length; |
631 |
if (len != 0) { |
632 |
// temp array holds those elements we know we want to keep |
633 |
int newlen = 0; |
634 |
Object[] temp = new Object[len]; |
635 |
for (int i = 0; i < len; ++i) { |
636 |
Object element = elements[i]; |
637 |
if (!c.contains(element)) |
638 |
temp[newlen++] = element; |
639 |
} |
640 |
if (newlen != len) { |
641 |
setArray(Arrays.copyOf(temp, newlen)); |
642 |
return true; |
643 |
} |
644 |
} |
645 |
return false; |
646 |
} finally { |
647 |
lock.unlock(); |
648 |
} |
649 |
} |
650 |
|
651 |
/** |
652 |
* Retains only the elements in this list that are contained in the |
653 |
* specified collection. In other words, removes from this list all of |
654 |
* its elements that are not contained in the specified collection. |
655 |
* |
656 |
* @param c collection containing elements to be retained in this list |
657 |
* @return {@code true} if this list changed as a result of the call |
658 |
* @throws ClassCastException if the class of an element of this list |
659 |
* is incompatible with the specified collection |
660 |
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
661 |
* @throws NullPointerException if this list contains a null element and the |
662 |
* specified collection does not permit null elements |
663 |
* (<a href="../Collection.html#optional-restrictions">optional</a>), |
664 |
* or if the specified collection is null |
665 |
* @see #remove(Object) |
666 |
*/ |
667 |
public boolean retainAll(Collection<?> c) { |
668 |
if (c == null) throw new NullPointerException(); |
669 |
final ReentrantLock lock = this.lock; |
670 |
lock.lock(); |
671 |
try { |
672 |
Object[] elements = getArray(); |
673 |
int len = elements.length; |
674 |
if (len != 0) { |
675 |
// temp array holds those elements we know we want to keep |
676 |
int newlen = 0; |
677 |
Object[] temp = new Object[len]; |
678 |
for (int i = 0; i < len; ++i) { |
679 |
Object element = elements[i]; |
680 |
if (c.contains(element)) |
681 |
temp[newlen++] = element; |
682 |
} |
683 |
if (newlen != len) { |
684 |
setArray(Arrays.copyOf(temp, newlen)); |
685 |
return true; |
686 |
} |
687 |
} |
688 |
return false; |
689 |
} finally { |
690 |
lock.unlock(); |
691 |
} |
692 |
} |
693 |
|
694 |
/** |
695 |
* Appends all of the elements in the specified collection that |
696 |
* are not already contained in this list, to the end of |
697 |
* this list, in the order that they are returned by the |
698 |
* specified collection's iterator. |
699 |
* |
700 |
* @param c collection containing elements to be added to this list |
701 |
* @return the number of elements added |
702 |
* @throws NullPointerException if the specified collection is null |
703 |
* @see #addIfAbsent(Object) |
704 |
*/ |
705 |
public int addAllAbsent(Collection<? extends E> c) { |
706 |
Object[] cs = c.toArray(); |
707 |
if (cs.length == 0) |
708 |
return 0; |
709 |
Object[] uniq = new Object[cs.length]; |
710 |
final ReentrantLock lock = this.lock; |
711 |
lock.lock(); |
712 |
try { |
713 |
Object[] elements = getArray(); |
714 |
int len = elements.length; |
715 |
int added = 0; |
716 |
for (int i = 0; i < cs.length; ++i) { // scan for duplicates |
717 |
Object e = cs[i]; |
718 |
if (indexOf(e, elements, 0, len) < 0 && |
719 |
indexOf(e, uniq, 0, added) < 0) |
720 |
uniq[added++] = e; |
721 |
} |
722 |
if (added > 0) { |
723 |
Object[] newElements = Arrays.copyOf(elements, len + added); |
724 |
System.arraycopy(uniq, 0, newElements, len, added); |
725 |
setArray(newElements); |
726 |
} |
727 |
return added; |
728 |
} finally { |
729 |
lock.unlock(); |
730 |
} |
731 |
} |
732 |
|
733 |
/** |
734 |
* Removes all of the elements from this list. |
735 |
* The list will be empty after this call returns. |
736 |
*/ |
737 |
public void clear() { |
738 |
final ReentrantLock lock = this.lock; |
739 |
lock.lock(); |
740 |
try { |
741 |
setArray(new Object[0]); |
742 |
} finally { |
743 |
lock.unlock(); |
744 |
} |
745 |
} |
746 |
|
747 |
/** |
748 |
* Appends all of the elements in the specified collection to the end |
749 |
* of this list, in the order that they are returned by the specified |
750 |
* collection's iterator. |
751 |
* |
752 |
* @param c collection containing elements to be added to this list |
753 |
* @return {@code true} if this list changed as a result of the call |
754 |
* @throws NullPointerException if the specified collection is null |
755 |
* @see #add(Object) |
756 |
*/ |
757 |
public boolean addAll(Collection<? extends E> c) { |
758 |
Object[] cs = c.toArray(); |
759 |
if (cs.length == 0) |
760 |
return false; |
761 |
final ReentrantLock lock = this.lock; |
762 |
lock.lock(); |
763 |
try { |
764 |
Object[] elements = getArray(); |
765 |
int len = elements.length; |
766 |
Object[] newElements = Arrays.copyOf(elements, len + cs.length); |
767 |
System.arraycopy(cs, 0, newElements, len, cs.length); |
768 |
setArray(newElements); |
769 |
return true; |
770 |
} finally { |
771 |
lock.unlock(); |
772 |
} |
773 |
} |
774 |
|
775 |
/** |
776 |
* Inserts all of the elements in the specified collection into this |
777 |
* list, starting at the specified position. Shifts the element |
778 |
* currently at that position (if any) and any subsequent elements to |
779 |
* the right (increases their indices). The new elements will appear |
780 |
* in this list in the order that they are returned by the |
781 |
* specified collection's iterator. |
782 |
* |
783 |
* @param index index at which to insert the first element |
784 |
* from the specified collection |
785 |
* @param c collection containing elements to be added to this list |
786 |
* @return {@code true} if this list changed as a result of the call |
787 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
788 |
* @throws NullPointerException if the specified collection is null |
789 |
* @see #add(int,Object) |
790 |
*/ |
791 |
public boolean addAll(int index, Collection<? extends E> c) { |
792 |
Object[] cs = c.toArray(); |
793 |
final ReentrantLock lock = this.lock; |
794 |
lock.lock(); |
795 |
try { |
796 |
Object[] elements = getArray(); |
797 |
int len = elements.length; |
798 |
if (index > len || index < 0) |
799 |
throw new IndexOutOfBoundsException("Index: "+index+ |
800 |
", Size: "+len); |
801 |
if (cs.length == 0) |
802 |
return false; |
803 |
int numMoved = len - index; |
804 |
Object[] newElements; |
805 |
if (numMoved == 0) |
806 |
newElements = Arrays.copyOf(elements, len + cs.length); |
807 |
else { |
808 |
newElements = new Object[len + cs.length]; |
809 |
System.arraycopy(elements, 0, newElements, 0, index); |
810 |
System.arraycopy(elements, index, |
811 |
newElements, index + cs.length, |
812 |
numMoved); |
813 |
} |
814 |
System.arraycopy(cs, 0, newElements, index, cs.length); |
815 |
setArray(newElements); |
816 |
return true; |
817 |
} finally { |
818 |
lock.unlock(); |
819 |
} |
820 |
} |
821 |
|
822 |
/** |
823 |
* Saves this list to a stream (that is, serializes it). |
824 |
* |
825 |
* @serialData The length of the array backing the list is emitted |
826 |
* (int), followed by all of its elements (each an Object) |
827 |
* in the proper order. |
828 |
*/ |
829 |
private void writeObject(java.io.ObjectOutputStream s) |
830 |
throws java.io.IOException { |
831 |
|
832 |
s.defaultWriteObject(); |
833 |
|
834 |
Object[] elements = getArray(); |
835 |
// Write out array length |
836 |
s.writeInt(elements.length); |
837 |
|
838 |
// Write out all elements in the proper order. |
839 |
for (Object element : elements) |
840 |
s.writeObject(element); |
841 |
} |
842 |
|
843 |
/** |
844 |
* Reconstitutes this list from a stream (that is, deserializes it). |
845 |
*/ |
846 |
private void readObject(java.io.ObjectInputStream s) |
847 |
throws java.io.IOException, ClassNotFoundException { |
848 |
|
849 |
s.defaultReadObject(); |
850 |
|
851 |
// bind to new lock |
852 |
resetLock(); |
853 |
|
854 |
// Read in array length and allocate array |
855 |
int len = s.readInt(); |
856 |
Object[] elements = new Object[len]; |
857 |
|
858 |
// Read in all elements in the proper order. |
859 |
for (int i = 0; i < len; i++) |
860 |
elements[i] = s.readObject(); |
861 |
setArray(elements); |
862 |
} |
863 |
|
864 |
/** |
865 |
* Returns a string representation of this list. The string |
866 |
* representation consists of the string representations of the list's |
867 |
* elements in the order they are returned by its iterator, enclosed in |
868 |
* square brackets ({@code "[]"}). Adjacent elements are separated by |
869 |
* the characters {@code ", "} (comma and space). Elements are |
870 |
* converted to strings as by {@link String#valueOf(Object)}. |
871 |
* |
872 |
* @return a string representation of this list |
873 |
*/ |
874 |
public String toString() { |
875 |
return Arrays.toString(getArray()); |
876 |
} |
877 |
|
878 |
/** |
879 |
* Compares the specified object with this list for equality. |
880 |
* Returns {@code true} if the specified object is the same object |
881 |
* as this object, or if it is also a {@link List} and the sequence |
882 |
* of elements returned by an {@linkplain List#iterator() iterator} |
883 |
* over the specified list is the same as the sequence returned by |
884 |
* an iterator over this list. The two sequences are considered to |
885 |
* be the same if they have the same length and corresponding |
886 |
* elements at the same position in the sequence are <em>equal</em>. |
887 |
* Two elements {@code e1} and {@code e2} are considered |
888 |
* <em>equal</em> if {@code (e1==null ? e2==null : e1.equals(e2))}. |
889 |
* |
890 |
* @param o the object to be compared for equality with this list |
891 |
* @return {@code true} if the specified object is equal to this list |
892 |
*/ |
893 |
public boolean equals(Object o) { |
894 |
if (o == this) |
895 |
return true; |
896 |
if (!(o instanceof List)) |
897 |
return false; |
898 |
|
899 |
List<?> list = (List<?>)(o); |
900 |
Iterator<?> it = list.iterator(); |
901 |
Object[] elements = getArray(); |
902 |
int len = elements.length; |
903 |
for (int i = 0; i < len; ++i) |
904 |
if (!it.hasNext() || !eq(elements[i], it.next())) |
905 |
return false; |
906 |
if (it.hasNext()) |
907 |
return false; |
908 |
return true; |
909 |
} |
910 |
|
911 |
/** |
912 |
* Returns the hash code value for this list. |
913 |
* |
914 |
* <p>This implementation uses the definition in {@link List#hashCode}. |
915 |
* |
916 |
* @return the hash code value for this list |
917 |
*/ |
918 |
public int hashCode() { |
919 |
int hashCode = 1; |
920 |
Object[] elements = getArray(); |
921 |
int len = elements.length; |
922 |
for (int i = 0; i < len; ++i) { |
923 |
Object obj = elements[i]; |
924 |
hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode()); |
925 |
} |
926 |
return hashCode; |
927 |
} |
928 |
|
929 |
/** |
930 |
* Returns an iterator over the elements in this list in proper sequence. |
931 |
* |
932 |
* <p>The returned iterator provides a snapshot of the state of the list |
933 |
* when the iterator was constructed. No synchronization is needed while |
934 |
* traversing the iterator. The iterator does <em>NOT</em> support the |
935 |
* {@code remove} method. |
936 |
* |
937 |
* @return an iterator over the elements in this list in proper sequence |
938 |
*/ |
939 |
public Iterator<E> iterator() { |
940 |
return new COWIterator<E>(getArray(), 0); |
941 |
} |
942 |
|
943 |
/** |
944 |
* {@inheritDoc} |
945 |
* |
946 |
* <p>The returned iterator provides a snapshot of the state of the list |
947 |
* when the iterator was constructed. No synchronization is needed while |
948 |
* traversing the iterator. The iterator does <em>NOT</em> support the |
949 |
* {@code remove}, {@code set} or {@code add} methods. |
950 |
*/ |
951 |
public ListIterator<E> listIterator() { |
952 |
return new COWIterator<E>(getArray(), 0); |
953 |
} |
954 |
|
955 |
/** |
956 |
* {@inheritDoc} |
957 |
* |
958 |
* <p>The returned iterator provides a snapshot of the state of the list |
959 |
* when the iterator was constructed. No synchronization is needed while |
960 |
* traversing the iterator. The iterator does <em>NOT</em> support the |
961 |
* {@code remove}, {@code set} or {@code add} methods. |
962 |
* |
963 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
964 |
*/ |
965 |
public ListIterator<E> listIterator(int index) { |
966 |
Object[] elements = getArray(); |
967 |
int len = elements.length; |
968 |
if (index < 0 || index > len) |
969 |
throw new IndexOutOfBoundsException("Index: "+index); |
970 |
|
971 |
return new COWIterator<E>(elements, index); |
972 |
} |
973 |
|
974 |
private static class COWIterator<E> implements ListIterator<E> { |
975 |
/** Snapshot of the array */ |
976 |
private final Object[] snapshot; |
977 |
/** Index of element to be returned by subsequent call to next. */ |
978 |
private int cursor; |
979 |
|
980 |
COWIterator(Object[] elements, int initialCursor) { |
981 |
cursor = initialCursor; |
982 |
snapshot = elements; |
983 |
} |
984 |
|
985 |
public boolean hasNext() { |
986 |
return cursor < snapshot.length; |
987 |
} |
988 |
|
989 |
public boolean hasPrevious() { |
990 |
return cursor > 0; |
991 |
} |
992 |
|
993 |
@SuppressWarnings("unchecked") |
994 |
public E next() { |
995 |
if (! hasNext()) |
996 |
throw new NoSuchElementException(); |
997 |
return (E) snapshot[cursor++]; |
998 |
} |
999 |
|
1000 |
@SuppressWarnings("unchecked") |
1001 |
public E previous() { |
1002 |
if (! hasPrevious()) |
1003 |
throw new NoSuchElementException(); |
1004 |
return (E) snapshot[--cursor]; |
1005 |
} |
1006 |
|
1007 |
public int nextIndex() { |
1008 |
return cursor; |
1009 |
} |
1010 |
|
1011 |
public int previousIndex() { |
1012 |
return cursor-1; |
1013 |
} |
1014 |
|
1015 |
/** |
1016 |
* Not supported. Always throws UnsupportedOperationException. |
1017 |
* @throws UnsupportedOperationException always; {@code remove} |
1018 |
* is not supported by this iterator. |
1019 |
*/ |
1020 |
public void remove() { |
1021 |
throw new UnsupportedOperationException(); |
1022 |
} |
1023 |
|
1024 |
/** |
1025 |
* Not supported. Always throws UnsupportedOperationException. |
1026 |
* @throws UnsupportedOperationException always; {@code set} |
1027 |
* is not supported by this iterator. |
1028 |
*/ |
1029 |
public void set(E e) { |
1030 |
throw new UnsupportedOperationException(); |
1031 |
} |
1032 |
|
1033 |
/** |
1034 |
* Not supported. Always throws UnsupportedOperationException. |
1035 |
* @throws UnsupportedOperationException always; {@code add} |
1036 |
* is not supported by this iterator. |
1037 |
*/ |
1038 |
public void add(E e) { |
1039 |
throw new UnsupportedOperationException(); |
1040 |
} |
1041 |
} |
1042 |
|
1043 |
/** |
1044 |
* Returns a view of the portion of this list between |
1045 |
* {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. |
1046 |
* The returned list is backed by this list, so changes in the |
1047 |
* returned list are reflected in this list. |
1048 |
* |
1049 |
* <p>The semantics of the list returned by this method become |
1050 |
* undefined if the backing list (i.e., this list) is modified in |
1051 |
* any way other than via the returned list. |
1052 |
* |
1053 |
* @param fromIndex low endpoint (inclusive) of the subList |
1054 |
* @param toIndex high endpoint (exclusive) of the subList |
1055 |
* @return a view of the specified range within this list |
1056 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
1057 |
*/ |
1058 |
public List<E> subList(int fromIndex, int toIndex) { |
1059 |
final ReentrantLock lock = this.lock; |
1060 |
lock.lock(); |
1061 |
try { |
1062 |
Object[] elements = getArray(); |
1063 |
int len = elements.length; |
1064 |
if (fromIndex < 0 || toIndex > len || fromIndex > toIndex) |
1065 |
throw new IndexOutOfBoundsException(); |
1066 |
return new COWSubList<E>(this, fromIndex, toIndex); |
1067 |
} finally { |
1068 |
lock.unlock(); |
1069 |
} |
1070 |
} |
1071 |
|
1072 |
/** |
1073 |
* Sublist for CopyOnWriteArrayList. |
1074 |
* This class extends AbstractList merely for convenience, to |
1075 |
* avoid having to define addAll, etc. This doesn't hurt, but |
1076 |
* is wasteful. This class does not need or use modCount |
1077 |
* mechanics in AbstractList, but does need to check for |
1078 |
* concurrent modification using similar mechanics. On each |
1079 |
* operation, the array that we expect the backing list to use |
1080 |
* is checked and updated. Since we do this for all of the |
1081 |
* base operations invoked by those defined in AbstractList, |
1082 |
* all is well. While inefficient, this is not worth |
1083 |
* improving. The kinds of list operations inherited from |
1084 |
* AbstractList are already so slow on COW sublists that |
1085 |
* adding a bit more space/time doesn't seem even noticeable. |
1086 |
*/ |
1087 |
private static class COWSubList<E> |
1088 |
extends AbstractList<E> |
1089 |
implements RandomAccess |
1090 |
{ |
1091 |
private final CopyOnWriteArrayList<E> l; |
1092 |
private final int offset; |
1093 |
private int size; |
1094 |
private Object[] expectedArray; |
1095 |
|
1096 |
// only call this holding l's lock |
1097 |
COWSubList(CopyOnWriteArrayList<E> list, |
1098 |
int fromIndex, int toIndex) { |
1099 |
l = list; |
1100 |
expectedArray = l.getArray(); |
1101 |
offset = fromIndex; |
1102 |
size = toIndex - fromIndex; |
1103 |
} |
1104 |
|
1105 |
// only call this holding l's lock |
1106 |
private void checkForComodification() { |
1107 |
if (l.getArray() != expectedArray) |
1108 |
throw new ConcurrentModificationException(); |
1109 |
} |
1110 |
|
1111 |
// only call this holding l's lock |
1112 |
private void rangeCheck(int index) { |
1113 |
if (index < 0 || index >= size) |
1114 |
throw new IndexOutOfBoundsException("Index: "+index+ |
1115 |
",Size: "+size); |
1116 |
} |
1117 |
|
1118 |
public E set(int index, E element) { |
1119 |
final ReentrantLock lock = l.lock; |
1120 |
lock.lock(); |
1121 |
try { |
1122 |
rangeCheck(index); |
1123 |
checkForComodification(); |
1124 |
E x = l.set(index+offset, element); |
1125 |
expectedArray = l.getArray(); |
1126 |
return x; |
1127 |
} finally { |
1128 |
lock.unlock(); |
1129 |
} |
1130 |
} |
1131 |
|
1132 |
public E get(int index) { |
1133 |
final ReentrantLock lock = l.lock; |
1134 |
lock.lock(); |
1135 |
try { |
1136 |
rangeCheck(index); |
1137 |
checkForComodification(); |
1138 |
return l.get(index+offset); |
1139 |
} finally { |
1140 |
lock.unlock(); |
1141 |
} |
1142 |
} |
1143 |
|
1144 |
public int size() { |
1145 |
final ReentrantLock lock = l.lock; |
1146 |
lock.lock(); |
1147 |
try { |
1148 |
checkForComodification(); |
1149 |
return size; |
1150 |
} finally { |
1151 |
lock.unlock(); |
1152 |
} |
1153 |
} |
1154 |
|
1155 |
public void add(int index, E element) { |
1156 |
final ReentrantLock lock = l.lock; |
1157 |
lock.lock(); |
1158 |
try { |
1159 |
checkForComodification(); |
1160 |
if (index < 0 || index > size) |
1161 |
throw new IndexOutOfBoundsException(); |
1162 |
l.add(index+offset, element); |
1163 |
expectedArray = l.getArray(); |
1164 |
size++; |
1165 |
} finally { |
1166 |
lock.unlock(); |
1167 |
} |
1168 |
} |
1169 |
|
1170 |
public void clear() { |
1171 |
final ReentrantLock lock = l.lock; |
1172 |
lock.lock(); |
1173 |
try { |
1174 |
checkForComodification(); |
1175 |
l.removeRange(offset, offset+size); |
1176 |
expectedArray = l.getArray(); |
1177 |
size = 0; |
1178 |
} finally { |
1179 |
lock.unlock(); |
1180 |
} |
1181 |
} |
1182 |
|
1183 |
public E remove(int index) { |
1184 |
final ReentrantLock lock = l.lock; |
1185 |
lock.lock(); |
1186 |
try { |
1187 |
rangeCheck(index); |
1188 |
checkForComodification(); |
1189 |
E result = l.remove(index+offset); |
1190 |
expectedArray = l.getArray(); |
1191 |
size--; |
1192 |
return result; |
1193 |
} finally { |
1194 |
lock.unlock(); |
1195 |
} |
1196 |
} |
1197 |
|
1198 |
public boolean remove(Object o) { |
1199 |
int index = indexOf(o); |
1200 |
if (index == -1) |
1201 |
return false; |
1202 |
remove(index); |
1203 |
return true; |
1204 |
} |
1205 |
|
1206 |
public Iterator<E> iterator() { |
1207 |
final ReentrantLock lock = l.lock; |
1208 |
lock.lock(); |
1209 |
try { |
1210 |
checkForComodification(); |
1211 |
return new COWSubListIterator<E>(l, 0, offset, size); |
1212 |
} finally { |
1213 |
lock.unlock(); |
1214 |
} |
1215 |
} |
1216 |
|
1217 |
public ListIterator<E> listIterator(int index) { |
1218 |
final ReentrantLock lock = l.lock; |
1219 |
lock.lock(); |
1220 |
try { |
1221 |
checkForComodification(); |
1222 |
if (index < 0 || index > size) |
1223 |
throw new IndexOutOfBoundsException("Index: "+index+ |
1224 |
", Size: "+size); |
1225 |
return new COWSubListIterator<E>(l, index, offset, size); |
1226 |
} finally { |
1227 |
lock.unlock(); |
1228 |
} |
1229 |
} |
1230 |
|
1231 |
public List<E> subList(int fromIndex, int toIndex) { |
1232 |
final ReentrantLock lock = l.lock; |
1233 |
lock.lock(); |
1234 |
try { |
1235 |
checkForComodification(); |
1236 |
if (fromIndex < 0 || toIndex > size || fromIndex > toIndex) |
1237 |
throw new IndexOutOfBoundsException(); |
1238 |
return new COWSubList<E>(l, fromIndex + offset, |
1239 |
toIndex + offset); |
1240 |
} finally { |
1241 |
lock.unlock(); |
1242 |
} |
1243 |
} |
1244 |
|
1245 |
} |
1246 |
|
1247 |
|
1248 |
private static class COWSubListIterator<E> implements ListIterator<E> { |
1249 |
private final ListIterator<E> it; |
1250 |
private final int offset; |
1251 |
private final int size; |
1252 |
|
1253 |
COWSubListIterator(List<E> l, int index, int offset, int size) { |
1254 |
this.offset = offset; |
1255 |
this.size = size; |
1256 |
it = l.listIterator(index+offset); |
1257 |
} |
1258 |
|
1259 |
public boolean hasNext() { |
1260 |
return nextIndex() < size; |
1261 |
} |
1262 |
|
1263 |
public E next() { |
1264 |
if (hasNext()) |
1265 |
return it.next(); |
1266 |
else |
1267 |
throw new NoSuchElementException(); |
1268 |
} |
1269 |
|
1270 |
public boolean hasPrevious() { |
1271 |
return previousIndex() >= 0; |
1272 |
} |
1273 |
|
1274 |
public E previous() { |
1275 |
if (hasPrevious()) |
1276 |
return it.previous(); |
1277 |
else |
1278 |
throw new NoSuchElementException(); |
1279 |
} |
1280 |
|
1281 |
public int nextIndex() { |
1282 |
return it.nextIndex() - offset; |
1283 |
} |
1284 |
|
1285 |
public int previousIndex() { |
1286 |
return it.previousIndex() - offset; |
1287 |
} |
1288 |
|
1289 |
public void remove() { |
1290 |
throw new UnsupportedOperationException(); |
1291 |
} |
1292 |
|
1293 |
public void set(E e) { |
1294 |
throw new UnsupportedOperationException(); |
1295 |
} |
1296 |
|
1297 |
public void add(E e) { |
1298 |
throw new UnsupportedOperationException(); |
1299 |
} |
1300 |
} |
1301 |
|
1302 |
// Support for resetting lock while deserializing |
1303 |
private void resetLock() { |
1304 |
UNSAFE.putObjectVolatile(this, lockOffset, new ReentrantLock()); |
1305 |
} |
1306 |
private static final sun.misc.Unsafe UNSAFE; |
1307 |
private static final long lockOffset; |
1308 |
static { |
1309 |
try { |
1310 |
UNSAFE = sun.misc.Unsafe.getUnsafe(); |
1311 |
Class<?> k = CopyOnWriteArrayList.class; |
1312 |
lockOffset = UNSAFE.objectFieldOffset |
1313 |
(k.getDeclaredField("lock")); |
1314 |
} catch (Exception e) { |
1315 |
throw new Error(e); |
1316 |
} |
1317 |
} |
1318 |
} |