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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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import java.util.*; |
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import java.util.concurrent.locks.*; |
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import sun.misc.Unsafe; |
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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 (<tt>add</tt>, <tt>set</tt>, 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 <tt>ConcurrentModificationException</tt>. |
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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 (<tt>remove</tt>, <tt>set</tt>, and |
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* <tt>add</tt>) are not supported. These methods throw |
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* <tt>UnsupportedOperationException</tt>. |
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* |
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* <p>All elements are permitted, including <tt>null</tt>. |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* <p> |
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* Memory visibility effects: As with other concurrent collections, state |
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* changes to any object made prior to placing it into a <tt>CopyOnWriteArrayList</tt> |
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* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> |
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* that element is accessed via or removed from the <tt>CopyOnWriteArrayList</tt>. |
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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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transient final ReentrantLock lock = new ReentrantLock(); |
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|
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/** The array, accessed only via getArray/setArray. */ |
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private volatile transient Object[] array; |
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|
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Object[] getArray() { return array; } |
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void setArray(Object[] a) { array = a; } |
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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 = new Object[c.size()]; |
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int size = 0; |
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for (E e : c) |
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elements[size++] = e; |
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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 <tt>true</tt> if this list contains no elements. |
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* |
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* @return <tt>true</tt> 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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* Test 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 <tt>true</tt> if this list contains the specified element. |
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* More formally, returns <tt>true</tt> if and only if this list contains |
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* at least one element <tt>e</tt> 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 <tt>true</tt> 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 <tt>index</tt>, or returns -1 if |
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* the element is not found. |
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* More formally, returns the lowest index <tt>i</tt> 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 <tt>index</tt> or later in the list; |
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* <tt>-1</tt> 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 <tt>index</tt>, or returns -1 if |
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* the element is not found. |
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* More formally, returns the highest index <tt>i</tt> 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 <tt>index</tt> 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.) |
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* |
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* @return a clone of this list |
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*/ |
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public Object clone() { |
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try { |
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return super.clone(); |
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} catch (CloneNotSupportedException e) { |
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// this shouldn't happen, since we are Cloneable |
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throw new InternalError(); |
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} |
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} |
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|
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/** |
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* Returns an array containing all of the elements in this list |
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* in proper sequence (from first to last element). |
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* |
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* <p>The returned array will be "safe" in that no references to it are |
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* maintained by this list. (In other words, this method must allocate |
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* a new array). The caller is thus free to modify the returned array. |
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* |
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* <p>This method acts as bridge between array-based and collection-based |
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* APIs. |
269 |
* |
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* @return an array containing all the elements in this list |
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*/ |
272 |
public Object[] toArray() { |
273 |
Object[] elements = getArray(); |
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return Arrays.copyOf(elements, elements.length); |
275 |
} |
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|
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/** |
278 |
* Returns an array containing all of the elements in this list in |
279 |
* proper sequence (from first to last element); the runtime type of |
280 |
* the returned array is that of the specified array. If the list fits |
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* in the specified array, it is returned therein. Otherwise, a new |
282 |
* array is allocated with the runtime type of the specified array and |
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* the size of this list. |
284 |
* |
285 |
* <p>If this list fits in the specified array with room to spare |
286 |
* (i.e., the array has more elements than this list), the element in |
287 |
* the array immediately following the end of the list is set to |
288 |
* <tt>null</tt>. (This is useful in determining the length of this |
289 |
* list <i>only</i> if the caller knows that this list does not contain |
290 |
* any null elements.) |
291 |
* |
292 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
293 |
* array-based and collection-based APIs. Further, this method allows |
294 |
* precise control over the runtime type of the output array, and may, |
295 |
* under certain circumstances, be used to save allocation costs. |
296 |
* |
297 |
* <p>Suppose <tt>x</tt> is a list known to contain only strings. |
298 |
* The following code can be used to dump the list into a newly |
299 |
* allocated array of <tt>String</tt>: |
300 |
* |
301 |
* <pre> |
302 |
* String[] y = x.toArray(new String[0]);</pre> |
303 |
* |
304 |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
305 |
* <tt>toArray()</tt>. |
306 |
* |
307 |
* @param a the array into which the elements of the list are to |
308 |
* be stored, if it is big enough; otherwise, a new array of the |
309 |
* same runtime type is allocated for this purpose. |
310 |
* @return an array containing all the elements in this list |
311 |
* @throws ArrayStoreException if the runtime type of the specified array |
312 |
* is not a supertype of the runtime type of every element in |
313 |
* this list |
314 |
* @throws NullPointerException if the specified array is null |
315 |
*/ |
316 |
public <T> T[] toArray(T a[]) { |
317 |
Object[] elements = getArray(); |
318 |
int len = elements.length; |
319 |
if (a.length < len) |
320 |
return (T[]) Arrays.copyOf(elements, len, a.getClass()); |
321 |
else { |
322 |
System.arraycopy(elements, 0, a, 0, len); |
323 |
if (a.length > len) |
324 |
a[len] = null; |
325 |
return a; |
326 |
} |
327 |
} |
328 |
|
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// Positional Access Operations |
330 |
|
331 |
/** |
332 |
* {@inheritDoc} |
333 |
* |
334 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
335 |
*/ |
336 |
public E get(int index) { |
337 |
return (E)(getArray()[index]); |
338 |
} |
339 |
|
340 |
/** |
341 |
* Replaces the element at the specified position in this list with the |
342 |
* specified element. |
343 |
* |
344 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
345 |
*/ |
346 |
public E set(int index, E element) { |
347 |
final ReentrantLock lock = this.lock; |
348 |
lock.lock(); |
349 |
try { |
350 |
Object[] elements = getArray(); |
351 |
int len = elements.length; |
352 |
Object oldValue = elements[index]; |
353 |
|
354 |
if (oldValue != element) { |
355 |
Object[] newElements = Arrays.copyOf(elements, len); |
356 |
newElements[index] = element; |
357 |
setArray(newElements); |
358 |
} |
359 |
return (E)oldValue; |
360 |
} finally { |
361 |
lock.unlock(); |
362 |
} |
363 |
} |
364 |
|
365 |
/** |
366 |
* Appends the specified element to the end of this list. |
367 |
* |
368 |
* @param e element to be appended to this list |
369 |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
370 |
*/ |
371 |
public boolean add(E e) { |
372 |
final ReentrantLock lock = this.lock; |
373 |
lock.lock(); |
374 |
try { |
375 |
Object[] elements = getArray(); |
376 |
int len = elements.length; |
377 |
Object[] newElements = Arrays.copyOf(elements, len + 1); |
378 |
newElements[len] = e; |
379 |
setArray(newElements); |
380 |
return true; |
381 |
} finally { |
382 |
lock.unlock(); |
383 |
} |
384 |
} |
385 |
|
386 |
/** |
387 |
* Inserts the specified element at the specified position in this |
388 |
* list. Shifts the element currently at that position (if any) and |
389 |
* any subsequent elements to the right (adds one to their indices). |
390 |
* |
391 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
392 |
*/ |
393 |
public void add(int index, E element) { |
394 |
final ReentrantLock lock = this.lock; |
395 |
lock.lock(); |
396 |
try { |
397 |
Object[] elements = getArray(); |
398 |
int len = elements.length; |
399 |
if (index > len || index < 0) |
400 |
throw new IndexOutOfBoundsException("Index: "+index+ |
401 |
", Size: "+len); |
402 |
Object[] newElements; |
403 |
int numMoved = len - index; |
404 |
if (numMoved == 0) |
405 |
newElements = Arrays.copyOf(elements, len + 1); |
406 |
else { |
407 |
newElements = new Object[len + 1]; |
408 |
System.arraycopy(elements, 0, newElements, 0, index); |
409 |
System.arraycopy(elements, index, newElements, index + 1, |
410 |
numMoved); |
411 |
} |
412 |
newElements[index] = element; |
413 |
setArray(newElements); |
414 |
} finally { |
415 |
lock.unlock(); |
416 |
} |
417 |
} |
418 |
|
419 |
/** |
420 |
* Removes the element at the specified position in this list. |
421 |
* Shifts any subsequent elements to the left (subtracts one from their |
422 |
* indices). Returns the element that was removed from the list. |
423 |
* |
424 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
425 |
*/ |
426 |
public E remove(int index) { |
427 |
final ReentrantLock lock = this.lock; |
428 |
lock.lock(); |
429 |
try { |
430 |
Object[] elements = getArray(); |
431 |
int len = elements.length; |
432 |
Object oldValue = elements[index]; |
433 |
int numMoved = len - index - 1; |
434 |
if (numMoved == 0) |
435 |
setArray(Arrays.copyOf(elements, len - 1)); |
436 |
else { |
437 |
Object[] newElements = new Object[len - 1]; |
438 |
System.arraycopy(elements, 0, newElements, 0, index); |
439 |
System.arraycopy(elements, index + 1, newElements, index, |
440 |
numMoved); |
441 |
setArray(newElements); |
442 |
} |
443 |
return (E)oldValue; |
444 |
} finally { |
445 |
lock.unlock(); |
446 |
} |
447 |
} |
448 |
|
449 |
/** |
450 |
* Removes the first occurrence of the specified element from this list, |
451 |
* if it is present. If this list does not contain the element, it is |
452 |
* unchanged. More formally, removes the element with the lowest index |
453 |
* <tt>i</tt> such that |
454 |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> |
455 |
* (if such an element exists). Returns <tt>true</tt> if this list |
456 |
* contained the specified element (or equivalently, if this list |
457 |
* changed as a result of the call). |
458 |
* |
459 |
* @param o element to be removed from this list, if present |
460 |
* @return <tt>true</tt> if this list contained the specified element |
461 |
*/ |
462 |
public boolean remove(Object o) { |
463 |
final ReentrantLock lock = this.lock; |
464 |
lock.lock(); |
465 |
try { |
466 |
Object[] elements = getArray(); |
467 |
int len = elements.length; |
468 |
if (len != 0) { |
469 |
// Copy while searching for element to remove |
470 |
// This wins in the normal case of element being present |
471 |
int newlen = len - 1; |
472 |
Object[] newElements = new Object[newlen]; |
473 |
|
474 |
for (int i = 0; i < newlen; ++i) { |
475 |
if (eq(o, elements[i])) { |
476 |
// found one; copy remaining and exit |
477 |
for (int k = i + 1; k < len; ++k) |
478 |
newElements[k-1] = elements[k]; |
479 |
setArray(newElements); |
480 |
return true; |
481 |
} else |
482 |
newElements[i] = elements[i]; |
483 |
} |
484 |
|
485 |
// special handling for last cell |
486 |
if (eq(o, elements[newlen])) { |
487 |
setArray(newElements); |
488 |
return true; |
489 |
} |
490 |
} |
491 |
return false; |
492 |
} finally { |
493 |
lock.unlock(); |
494 |
} |
495 |
} |
496 |
|
497 |
/** |
498 |
* Removes from this list all of the elements whose index is between |
499 |
* <tt>fromIndex</tt>, inclusive, and <tt>toIndex</tt>, exclusive. |
500 |
* Shifts any succeeding elements to the left (reduces their index). |
501 |
* This call shortens the list by <tt>(toIndex - fromIndex)</tt> elements. |
502 |
* (If <tt>toIndex==fromIndex</tt>, this operation has no effect.) |
503 |
* |
504 |
* @param fromIndex index of first element to be removed |
505 |
* @param toIndex index after last element to be removed |
506 |
* @throws IndexOutOfBoundsException if fromIndex or toIndex out of |
507 |
* range (fromIndex < 0 || fromIndex >= size() || toIndex |
508 |
* > size() || toIndex < fromIndex) |
509 |
*/ |
510 |
private void removeRange(int fromIndex, int toIndex) { |
511 |
final ReentrantLock lock = this.lock; |
512 |
lock.lock(); |
513 |
try { |
514 |
Object[] elements = getArray(); |
515 |
int len = elements.length; |
516 |
|
517 |
if (fromIndex < 0 || fromIndex >= len || |
518 |
toIndex > len || toIndex < fromIndex) |
519 |
throw new IndexOutOfBoundsException(); |
520 |
int newlen = len - (toIndex - fromIndex); |
521 |
int numMoved = len - toIndex; |
522 |
if (numMoved == 0) |
523 |
setArray(Arrays.copyOf(elements, newlen)); |
524 |
else { |
525 |
Object[] newElements = new Object[newlen]; |
526 |
System.arraycopy(elements, 0, newElements, 0, fromIndex); |
527 |
System.arraycopy(elements, toIndex, newElements, |
528 |
fromIndex, numMoved); |
529 |
setArray(newElements); |
530 |
} |
531 |
} finally { |
532 |
lock.unlock(); |
533 |
} |
534 |
} |
535 |
|
536 |
/** |
537 |
* Append the element if not present. |
538 |
* |
539 |
* @param e element to be added to this list, if absent |
540 |
* @return <tt>true</tt> if the element was added |
541 |
*/ |
542 |
public boolean addIfAbsent(E e) { |
543 |
final ReentrantLock lock = this.lock; |
544 |
lock.lock(); |
545 |
try { |
546 |
// Copy while checking if already present. |
547 |
// This wins in the most common case where it is not present |
548 |
Object[] elements = getArray(); |
549 |
int len = elements.length; |
550 |
Object[] newElements = new Object[len + 1]; |
551 |
for (int i = 0; i < len; ++i) { |
552 |
if (eq(e, elements[i])) |
553 |
return false; // exit, throwing away copy |
554 |
else |
555 |
newElements[i] = elements[i]; |
556 |
} |
557 |
newElements[len] = e; |
558 |
setArray(newElements); |
559 |
return true; |
560 |
} finally { |
561 |
lock.unlock(); |
562 |
} |
563 |
} |
564 |
|
565 |
/** |
566 |
* Returns <tt>true</tt> if this list contains all of the elements of the |
567 |
* specified collection. |
568 |
* |
569 |
* @param c collection to be checked for containment in this list |
570 |
* @return <tt>true</tt> if this list contains all of the elements of the |
571 |
* specified collection |
572 |
* @throws NullPointerException if the specified collection is null |
573 |
* @see #contains(Object) |
574 |
*/ |
575 |
public boolean containsAll(Collection<?> c) { |
576 |
Object[] elements = getArray(); |
577 |
int len = elements.length; |
578 |
for (Object e : c) { |
579 |
if (indexOf(e, elements, 0, len) < 0) |
580 |
return false; |
581 |
} |
582 |
return true; |
583 |
} |
584 |
|
585 |
/** |
586 |
* Removes from this list all of its elements that are contained in |
587 |
* the specified collection. This is a particularly expensive operation |
588 |
* in this class because of the need for an internal temporary array. |
589 |
* |
590 |
* @param c collection containing elements to be removed from this list |
591 |
* @return <tt>true</tt> if this list changed as a result of the call |
592 |
* @throws ClassCastException if the class of an element of this list |
593 |
* is incompatible with the specified collection (optional) |
594 |
* @throws NullPointerException if this list contains a null element and the |
595 |
* specified collection does not permit null elements (optional), |
596 |
* or if the specified collection is null |
597 |
* @see #remove(Object) |
598 |
*/ |
599 |
public boolean removeAll(Collection<?> c) { |
600 |
final ReentrantLock lock = this.lock; |
601 |
lock.lock(); |
602 |
try { |
603 |
Object[] elements = getArray(); |
604 |
int len = elements.length; |
605 |
if (len != 0) { |
606 |
// temp array holds those elements we know we want to keep |
607 |
int newlen = 0; |
608 |
Object[] temp = new Object[len]; |
609 |
for (int i = 0; i < len; ++i) { |
610 |
Object element = elements[i]; |
611 |
if (!c.contains(element)) |
612 |
temp[newlen++] = element; |
613 |
} |
614 |
if (newlen != len) { |
615 |
setArray(Arrays.copyOf(temp, newlen)); |
616 |
return true; |
617 |
} |
618 |
} |
619 |
return false; |
620 |
} finally { |
621 |
lock.unlock(); |
622 |
} |
623 |
} |
624 |
|
625 |
/** |
626 |
* Retains only the elements in this list that are contained in the |
627 |
* specified collection. In other words, removes from this list all of |
628 |
* its elements that are not contained in the specified collection. |
629 |
* |
630 |
* @param c collection containing elements to be retained in this list |
631 |
* @return <tt>true</tt> if this list changed as a result of the call |
632 |
* @throws ClassCastException if the class of an element of this list |
633 |
* is incompatible with the specified collection (optional) |
634 |
* @throws NullPointerException if this list contains a null element and the |
635 |
* specified collection does not permit null elements (optional), |
636 |
* or if the specified collection is null |
637 |
* @see #remove(Object) |
638 |
*/ |
639 |
public boolean retainAll(Collection<?> c) { |
640 |
final ReentrantLock lock = this.lock; |
641 |
lock.lock(); |
642 |
try { |
643 |
Object[] elements = getArray(); |
644 |
int len = elements.length; |
645 |
if (len != 0) { |
646 |
// temp array holds those elements we know we want to keep |
647 |
int newlen = 0; |
648 |
Object[] temp = new Object[len]; |
649 |
for (int i = 0; i < len; ++i) { |
650 |
Object element = elements[i]; |
651 |
if (c.contains(element)) |
652 |
temp[newlen++] = element; |
653 |
} |
654 |
if (newlen != len) { |
655 |
setArray(Arrays.copyOf(temp, newlen)); |
656 |
return true; |
657 |
} |
658 |
} |
659 |
return false; |
660 |
} finally { |
661 |
lock.unlock(); |
662 |
} |
663 |
} |
664 |
|
665 |
/** |
666 |
* Appends all of the elements in the specified collection that |
667 |
* are not already contained in this list, to the end of |
668 |
* this list, in the order that they are returned by the |
669 |
* specified collection's iterator. |
670 |
* |
671 |
* @param c collection containing elements to be added to this list |
672 |
* @return the number of elements added |
673 |
* @throws NullPointerException if the specified collection is null |
674 |
* @see #addIfAbsent(Object) |
675 |
*/ |
676 |
public int addAllAbsent(Collection<? extends E> c) { |
677 |
int numNew = c.size(); |
678 |
if (numNew == 0) |
679 |
return 0; |
680 |
final ReentrantLock lock = this.lock; |
681 |
lock.lock(); |
682 |
try { |
683 |
Object[] elements = getArray(); |
684 |
int len = elements.length; |
685 |
|
686 |
Object[] temp = new Object[numNew]; |
687 |
int added = 0; |
688 |
for (E e : c) { |
689 |
if (indexOf(e, elements, 0, len) < 0 && |
690 |
indexOf(e, temp, 0, added) < 0) |
691 |
temp[added++] = e; |
692 |
} |
693 |
if (added != 0) { |
694 |
Object[] newElements = Arrays.copyOf(elements, len + added); |
695 |
System.arraycopy(temp, 0, newElements, len, added); |
696 |
setArray(newElements); |
697 |
} |
698 |
return added; |
699 |
} finally { |
700 |
lock.unlock(); |
701 |
} |
702 |
} |
703 |
|
704 |
/** |
705 |
* Removes all of the elements from this list. |
706 |
* The list will be empty after this call returns. |
707 |
*/ |
708 |
public void clear() { |
709 |
final ReentrantLock lock = this.lock; |
710 |
lock.lock(); |
711 |
try { |
712 |
setArray(new Object[0]); |
713 |
} finally { |
714 |
lock.unlock(); |
715 |
} |
716 |
} |
717 |
|
718 |
/** |
719 |
* Appends all of the elements in the specified collection to the end |
720 |
* of this list, in the order that they are returned by the specified |
721 |
* collection's iterator. |
722 |
* |
723 |
* @param c collection containing elements to be added to this list |
724 |
* @return <tt>true</tt> if this list changed as a result of the call |
725 |
* @throws NullPointerException if the specified collection is null |
726 |
* @see #add(Object) |
727 |
*/ |
728 |
public boolean addAll(Collection<? extends E> c) { |
729 |
int numNew = c.size(); |
730 |
if (numNew == 0) |
731 |
return false; |
732 |
final ReentrantLock lock = this.lock; |
733 |
lock.lock(); |
734 |
try { |
735 |
Object[] elements = getArray(); |
736 |
int len = elements.length; |
737 |
Object[] newElements = Arrays.copyOf(elements, len + numNew); |
738 |
for (E e : c) |
739 |
newElements[len++] = e; |
740 |
setArray(newElements); |
741 |
return true; |
742 |
} finally { |
743 |
lock.unlock(); |
744 |
} |
745 |
} |
746 |
|
747 |
/** |
748 |
* Inserts all of the elements in the specified collection into this |
749 |
* list, starting at the specified position. Shifts the element |
750 |
* currently at that position (if any) and any subsequent elements to |
751 |
* the right (increases their indices). The new elements will appear |
752 |
* in this list in the order that they are returned by the |
753 |
* specified collection's iterator. |
754 |
* |
755 |
* @param index index at which to insert the first element |
756 |
* from the specified collection |
757 |
* @param c collection containing elements to be added to this list |
758 |
* @return <tt>true</tt> if this list changed as a result of the call |
759 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
760 |
* @throws NullPointerException if the specified collection is null |
761 |
* @see #add(int,Object) |
762 |
*/ |
763 |
public boolean addAll(int index, Collection<? extends E> c) { |
764 |
int numNew = c.size(); |
765 |
final ReentrantLock lock = this.lock; |
766 |
lock.lock(); |
767 |
try { |
768 |
Object[] elements = getArray(); |
769 |
int len = elements.length; |
770 |
if (index > len || index < 0) |
771 |
throw new IndexOutOfBoundsException("Index: "+index+ |
772 |
", Size: "+len); |
773 |
if (numNew == 0) |
774 |
return false; |
775 |
int numMoved = len - index; |
776 |
Object[] newElements; |
777 |
if (numMoved == 0) |
778 |
newElements = Arrays.copyOf(elements, len + numNew); |
779 |
else { |
780 |
newElements = new Object[len + numNew]; |
781 |
System.arraycopy(elements, 0, newElements, 0, index); |
782 |
System.arraycopy(elements, index, |
783 |
newElements, index + numNew, |
784 |
numMoved); |
785 |
} |
786 |
for (E e : c) |
787 |
newElements[index++] = e; |
788 |
setArray(newElements); |
789 |
return true; |
790 |
} finally { |
791 |
lock.unlock(); |
792 |
} |
793 |
} |
794 |
|
795 |
/** |
796 |
* Save the state of the list to a stream (i.e., serialize it). |
797 |
* |
798 |
* @serialData The length of the array backing the list is emitted |
799 |
* (int), followed by all of its elements (each an Object) |
800 |
* in the proper order. |
801 |
* @param s the stream |
802 |
*/ |
803 |
private void writeObject(java.io.ObjectOutputStream s) |
804 |
throws java.io.IOException{ |
805 |
|
806 |
// Write out element count, and any hidden stuff |
807 |
s.defaultWriteObject(); |
808 |
|
809 |
Object[] elements = getArray(); |
810 |
int len = elements.length; |
811 |
// Write out array length |
812 |
s.writeInt(len); |
813 |
|
814 |
// Write out all elements in the proper order. |
815 |
for (int i = 0; i < len; i++) |
816 |
s.writeObject(elements[i]); |
817 |
} |
818 |
|
819 |
/** |
820 |
* Reconstitute the list from a stream (i.e., deserialize it). |
821 |
* @param s the stream |
822 |
*/ |
823 |
private void readObject(java.io.ObjectInputStream s) |
824 |
throws java.io.IOException, ClassNotFoundException { |
825 |
|
826 |
// Read in size, and any hidden stuff |
827 |
s.defaultReadObject(); |
828 |
|
829 |
// bind to new lock |
830 |
resetLock(); |
831 |
|
832 |
// Read in array length and allocate array |
833 |
int len = s.readInt(); |
834 |
Object[] elements = new Object[len]; |
835 |
|
836 |
// Read in all elements in the proper order. |
837 |
for (int i = 0; i < len; i++) |
838 |
elements[i] = s.readObject(); |
839 |
setArray(elements); |
840 |
} |
841 |
|
842 |
/** |
843 |
* Returns a string representation of this list, containing |
844 |
* the String representation of each element. |
845 |
*/ |
846 |
public String toString() { |
847 |
Object[] elements = getArray(); |
848 |
int maxIndex = elements.length - 1; |
849 |
StringBuilder sb = new StringBuilder(); |
850 |
sb.append("["); |
851 |
for (int i = 0; i <= maxIndex; i++) { |
852 |
sb.append(String.valueOf(elements[i])); |
853 |
if (i < maxIndex) |
854 |
sb.append(", "); |
855 |
} |
856 |
sb.append("]"); |
857 |
return sb.toString(); |
858 |
} |
859 |
|
860 |
/** |
861 |
* Compares the specified object with this list for equality. |
862 |
* Returns true if and only if the specified object is also a {@link |
863 |
* List}, both lists have the same size, and all corresponding pairs |
864 |
* of elements in the two lists are <em>equal</em>. (Two elements |
865 |
* <tt>e1</tt> and <tt>e2</tt> are <em>equal</em> if <tt>(e1==null ? |
866 |
* e2==null : e1.equals(e2))</tt>.) In other words, two lists are |
867 |
* defined to be equal if they contain the same elements in the same |
868 |
* order. |
869 |
* |
870 |
* @param o the object to be compared for equality with this list |
871 |
* @return <tt>true</tt> if the specified object is equal to this list |
872 |
*/ |
873 |
public boolean equals(Object o) { |
874 |
if (o == this) |
875 |
return true; |
876 |
if (!(o instanceof List)) |
877 |
return false; |
878 |
|
879 |
List<?> l2 = (List<?>)(o); |
880 |
if (size() != l2.size()) |
881 |
return false; |
882 |
|
883 |
ListIterator<?> e1 = listIterator(); |
884 |
ListIterator<?> e2 = l2.listIterator(); |
885 |
while (e1.hasNext()) { |
886 |
if (!eq(e1.next(), e2.next())) |
887 |
return false; |
888 |
} |
889 |
return true; |
890 |
} |
891 |
|
892 |
/** |
893 |
* Returns the hash code value for this list. |
894 |
* |
895 |
* <p>This implementation uses the definition in {@link List#hashCode}. |
896 |
* |
897 |
* @return the hash code value for this list |
898 |
*/ |
899 |
public int hashCode() { |
900 |
int hashCode = 1; |
901 |
Object[] elements = getArray(); |
902 |
int len = elements.length; |
903 |
for (int i = 0; i < len; ++i) { |
904 |
Object obj = elements[i]; |
905 |
hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode()); |
906 |
} |
907 |
return hashCode; |
908 |
} |
909 |
|
910 |
/** |
911 |
* Returns an iterator over the elements in this list in proper sequence. |
912 |
* |
913 |
* <p>The returned iterator provides a snapshot of the state of the list |
914 |
* when the iterator was constructed. No synchronization is needed while |
915 |
* traversing the iterator. The iterator does <em>NOT</em> support the |
916 |
* <tt>remove</tt> method. |
917 |
* |
918 |
* @return an iterator over the elements in this list in proper sequence |
919 |
*/ |
920 |
public Iterator<E> iterator() { |
921 |
return new COWIterator<E>(getArray(), 0); |
922 |
} |
923 |
|
924 |
/** |
925 |
* {@inheritDoc} |
926 |
* |
927 |
* <p>The returned iterator provides a snapshot of the state of the list |
928 |
* when the iterator was constructed. No synchronization is needed while |
929 |
* traversing the iterator. The iterator does <em>NOT</em> support the |
930 |
* <tt>remove</tt>, <tt>set</tt> or <tt>add</tt> methods. |
931 |
*/ |
932 |
public ListIterator<E> listIterator() { |
933 |
return new COWIterator<E>(getArray(), 0); |
934 |
} |
935 |
|
936 |
/** |
937 |
* {@inheritDoc} |
938 |
* |
939 |
* <p>The returned iterator provides a snapshot of the state of the list |
940 |
* when the iterator was constructed. No synchronization is needed while |
941 |
* traversing the iterator. The iterator does <em>NOT</em> support the |
942 |
* <tt>remove</tt>, <tt>set</tt> or <tt>add</tt> methods. |
943 |
* |
944 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
945 |
*/ |
946 |
public ListIterator<E> listIterator(final int index) { |
947 |
Object[] elements = getArray(); |
948 |
int len = elements.length; |
949 |
if (index<0 || index>len) |
950 |
throw new IndexOutOfBoundsException("Index: "+index); |
951 |
|
952 |
return new COWIterator<E>(elements, index); |
953 |
} |
954 |
|
955 |
private static class COWIterator<E> implements ListIterator<E> { |
956 |
/** Snapshot of the array **/ |
957 |
private final Object[] snapshot; |
958 |
/** Index of element to be returned by subsequent call to next. */ |
959 |
private int cursor; |
960 |
|
961 |
private COWIterator(Object[] elements, int initialCursor) { |
962 |
cursor = initialCursor; |
963 |
snapshot = elements; |
964 |
} |
965 |
|
966 |
public boolean hasNext() { |
967 |
return cursor < snapshot.length; |
968 |
} |
969 |
|
970 |
public boolean hasPrevious() { |
971 |
return cursor > 0; |
972 |
} |
973 |
|
974 |
public E next() { |
975 |
try { |
976 |
return (E)(snapshot[cursor++]); |
977 |
} catch (IndexOutOfBoundsException ex) { |
978 |
throw new NoSuchElementException(); |
979 |
} |
980 |
} |
981 |
|
982 |
public E previous() { |
983 |
try { |
984 |
return (E)(snapshot[--cursor]); |
985 |
} catch (IndexOutOfBoundsException e) { |
986 |
throw new NoSuchElementException(); |
987 |
} |
988 |
} |
989 |
|
990 |
public int nextIndex() { |
991 |
return cursor; |
992 |
} |
993 |
|
994 |
public int previousIndex() { |
995 |
return cursor-1; |
996 |
} |
997 |
|
998 |
/** |
999 |
* Not supported. Always throws UnsupportedOperationException. |
1000 |
* @throws UnsupportedOperationException always; <tt>remove</tt> |
1001 |
* is not supported by this iterator. |
1002 |
*/ |
1003 |
public void remove() { |
1004 |
throw new UnsupportedOperationException(); |
1005 |
} |
1006 |
|
1007 |
/** |
1008 |
* Not supported. Always throws UnsupportedOperationException. |
1009 |
* @throws UnsupportedOperationException always; <tt>set</tt> |
1010 |
* is not supported by this iterator. |
1011 |
*/ |
1012 |
public void set(E e) { |
1013 |
throw new UnsupportedOperationException(); |
1014 |
} |
1015 |
|
1016 |
/** |
1017 |
* Not supported. Always throws UnsupportedOperationException. |
1018 |
* @throws UnsupportedOperationException always; <tt>add</tt> |
1019 |
* is not supported by this iterator. |
1020 |
*/ |
1021 |
public void add(E e) { |
1022 |
throw new UnsupportedOperationException(); |
1023 |
} |
1024 |
} |
1025 |
|
1026 |
/** |
1027 |
* Returns a view of the portion of this list between |
1028 |
* <tt>fromIndex</tt>, inclusive, and <tt>toIndex</tt>, exclusive. |
1029 |
* The returned list is backed by this list, so changes in the |
1030 |
* returned list are reflected in this list, and vice-versa. |
1031 |
* While mutative operations are supported, they are probably not |
1032 |
* very useful for CopyOnWriteArrayLists. |
1033 |
* |
1034 |
* <p>The semantics of the list returned by this method become |
1035 |
* undefined if the backing list (i.e., this list) is |
1036 |
* <i>structurally modified</i> in any way other than via the |
1037 |
* returned list. (Structural modifications are those that change |
1038 |
* the size of the list, or otherwise perturb it in such a fashion |
1039 |
* that iterations in progress may yield incorrect results.) |
1040 |
* |
1041 |
* @param fromIndex low endpoint (inclusive) of the subList |
1042 |
* @param toIndex high endpoint (exclusive) of the subList |
1043 |
* @return a view of the specified range within this list |
1044 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
1045 |
*/ |
1046 |
public List<E> subList(int fromIndex, int toIndex) { |
1047 |
final ReentrantLock lock = this.lock; |
1048 |
lock.lock(); |
1049 |
try { |
1050 |
Object[] elements = getArray(); |
1051 |
int len = elements.length; |
1052 |
if (fromIndex < 0 || toIndex > len || fromIndex > toIndex) |
1053 |
throw new IndexOutOfBoundsException(); |
1054 |
return new COWSubList<E>(this, fromIndex, toIndex); |
1055 |
} finally { |
1056 |
lock.unlock(); |
1057 |
} |
1058 |
} |
1059 |
|
1060 |
/** |
1061 |
* Sublist for CopyOnWriteArrayList. |
1062 |
* This class extends AbstractList merely for convenience, to |
1063 |
* avoid having to define addAll, etc. This doesn't hurt, but |
1064 |
* is wasteful. This class does not need or use modCount |
1065 |
* mechanics in AbstractList, but does need to check for |
1066 |
* concurrent modification using similar mechanics. On each |
1067 |
* operation, the array that we expect the backing list to use |
1068 |
* is checked and updated. Since we do this for all of the |
1069 |
* base operations invoked by those defined in AbstractList, |
1070 |
* all is well. While inefficient, this is not worth |
1071 |
* improving. The kinds of list operations inherited from |
1072 |
* AbstractList are already so slow on COW sublists that |
1073 |
* adding a bit more space/time doesn't seem even noticeable. |
1074 |
*/ |
1075 |
private static class COWSubList<E> extends AbstractList<E> { |
1076 |
private final CopyOnWriteArrayList<E> l; |
1077 |
private final int offset; |
1078 |
private int size; |
1079 |
private Object[] expectedArray; |
1080 |
|
1081 |
// only call this holding l's lock |
1082 |
private COWSubList(CopyOnWriteArrayList<E> list, |
1083 |
int fromIndex, int toIndex) { |
1084 |
l = list; |
1085 |
expectedArray = l.getArray(); |
1086 |
offset = fromIndex; |
1087 |
size = toIndex - fromIndex; |
1088 |
} |
1089 |
|
1090 |
// only call this holding l's lock |
1091 |
private void checkForComodification() { |
1092 |
if (l.getArray() != expectedArray) |
1093 |
throw new ConcurrentModificationException(); |
1094 |
} |
1095 |
|
1096 |
// only call this holding l's lock |
1097 |
private void rangeCheck(int index) { |
1098 |
if (index<0 || index>=size) |
1099 |
throw new IndexOutOfBoundsException("Index: "+index+ |
1100 |
",Size: "+size); |
1101 |
} |
1102 |
|
1103 |
public E set(int index, E element) { |
1104 |
final ReentrantLock lock = l.lock; |
1105 |
lock.lock(); |
1106 |
try { |
1107 |
rangeCheck(index); |
1108 |
checkForComodification(); |
1109 |
E x = l.set(index+offset, element); |
1110 |
expectedArray = l.getArray(); |
1111 |
return x; |
1112 |
} finally { |
1113 |
lock.unlock(); |
1114 |
} |
1115 |
} |
1116 |
|
1117 |
public E get(int index) { |
1118 |
final ReentrantLock lock = l.lock; |
1119 |
lock.lock(); |
1120 |
try { |
1121 |
rangeCheck(index); |
1122 |
checkForComodification(); |
1123 |
return l.get(index+offset); |
1124 |
} finally { |
1125 |
lock.unlock(); |
1126 |
} |
1127 |
} |
1128 |
|
1129 |
public int size() { |
1130 |
final ReentrantLock lock = l.lock; |
1131 |
lock.lock(); |
1132 |
try { |
1133 |
checkForComodification(); |
1134 |
return size; |
1135 |
} finally { |
1136 |
lock.unlock(); |
1137 |
} |
1138 |
} |
1139 |
|
1140 |
public void add(int index, E element) { |
1141 |
final ReentrantLock lock = l.lock; |
1142 |
lock.lock(); |
1143 |
try { |
1144 |
checkForComodification(); |
1145 |
if (index<0 || index>size) |
1146 |
throw new IndexOutOfBoundsException(); |
1147 |
l.add(index+offset, element); |
1148 |
expectedArray = l.getArray(); |
1149 |
size++; |
1150 |
} finally { |
1151 |
lock.unlock(); |
1152 |
} |
1153 |
} |
1154 |
|
1155 |
public void clear() { |
1156 |
final ReentrantLock lock = l.lock; |
1157 |
lock.lock(); |
1158 |
try { |
1159 |
checkForComodification(); |
1160 |
l.removeRange(offset, offset+size); |
1161 |
expectedArray = l.getArray(); |
1162 |
size = 0; |
1163 |
} finally { |
1164 |
lock.unlock(); |
1165 |
} |
1166 |
} |
1167 |
|
1168 |
public E remove(int index) { |
1169 |
final ReentrantLock lock = l.lock; |
1170 |
lock.lock(); |
1171 |
try { |
1172 |
rangeCheck(index); |
1173 |
checkForComodification(); |
1174 |
E result = l.remove(index+offset); |
1175 |
expectedArray = l.getArray(); |
1176 |
size--; |
1177 |
return result; |
1178 |
} finally { |
1179 |
lock.unlock(); |
1180 |
} |
1181 |
} |
1182 |
|
1183 |
public Iterator<E> iterator() { |
1184 |
final ReentrantLock lock = l.lock; |
1185 |
lock.lock(); |
1186 |
try { |
1187 |
checkForComodification(); |
1188 |
return new COWSubListIterator<E>(l, 0, offset, size); |
1189 |
} finally { |
1190 |
lock.unlock(); |
1191 |
} |
1192 |
} |
1193 |
|
1194 |
public ListIterator<E> listIterator(final int index) { |
1195 |
final ReentrantLock lock = l.lock; |
1196 |
lock.lock(); |
1197 |
try { |
1198 |
checkForComodification(); |
1199 |
if (index<0 || index>size) |
1200 |
throw new IndexOutOfBoundsException("Index: "+index+ |
1201 |
", Size: "+size); |
1202 |
return new COWSubListIterator<E>(l, index, offset, size); |
1203 |
} finally { |
1204 |
lock.unlock(); |
1205 |
} |
1206 |
} |
1207 |
|
1208 |
public List<E> subList(int fromIndex, int toIndex) { |
1209 |
final ReentrantLock lock = l.lock; |
1210 |
lock.lock(); |
1211 |
try { |
1212 |
checkForComodification(); |
1213 |
if (fromIndex<0 || toIndex>size) |
1214 |
throw new IndexOutOfBoundsException(); |
1215 |
return new COWSubList<E>(l, fromIndex + offset, |
1216 |
toIndex + offset); |
1217 |
} finally { |
1218 |
lock.unlock(); |
1219 |
} |
1220 |
} |
1221 |
|
1222 |
} |
1223 |
|
1224 |
|
1225 |
private static class COWSubListIterator<E> implements ListIterator<E> { |
1226 |
private final ListIterator<E> i; |
1227 |
private final int index; |
1228 |
private final int offset; |
1229 |
private final int size; |
1230 |
private COWSubListIterator(List<E> l, int index, int offset, |
1231 |
int size) { |
1232 |
this.index = index; |
1233 |
this.offset = offset; |
1234 |
this.size = size; |
1235 |
i = l.listIterator(index+offset); |
1236 |
} |
1237 |
|
1238 |
public boolean hasNext() { |
1239 |
return nextIndex() < size; |
1240 |
} |
1241 |
|
1242 |
public E next() { |
1243 |
if (hasNext()) |
1244 |
return i.next(); |
1245 |
else |
1246 |
throw new NoSuchElementException(); |
1247 |
} |
1248 |
|
1249 |
public boolean hasPrevious() { |
1250 |
return previousIndex() >= 0; |
1251 |
} |
1252 |
|
1253 |
public E previous() { |
1254 |
if (hasPrevious()) |
1255 |
return i.previous(); |
1256 |
else |
1257 |
throw new NoSuchElementException(); |
1258 |
} |
1259 |
|
1260 |
public int nextIndex() { |
1261 |
return i.nextIndex() - offset; |
1262 |
} |
1263 |
|
1264 |
public int previousIndex() { |
1265 |
return i.previousIndex() - offset; |
1266 |
} |
1267 |
|
1268 |
public void remove() { |
1269 |
throw new UnsupportedOperationException(); |
1270 |
} |
1271 |
|
1272 |
public void set(E e) { |
1273 |
throw new UnsupportedOperationException(); |
1274 |
} |
1275 |
|
1276 |
public void add(E e) { |
1277 |
throw new UnsupportedOperationException(); |
1278 |
} |
1279 |
} |
1280 |
|
1281 |
// Support for resetting lock while deserializing |
1282 |
private static final Unsafe unsafe = Unsafe.getUnsafe(); |
1283 |
private static final long lockOffset; |
1284 |
static { |
1285 |
try { |
1286 |
lockOffset = unsafe.objectFieldOffset |
1287 |
(CopyOnWriteArrayList.class.getDeclaredField("lock")); |
1288 |
} catch (Exception ex) { throw new Error(ex); } |
1289 |
} |
1290 |
private void resetLock() { |
1291 |
unsafe.putObjectVolatile(this, lockOffset, new ReentrantLock()); |
1292 |
} |
1293 |
|
1294 |
} |