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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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|
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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 (add, set, and so on) are implemented by making a fresh |
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* 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 (remove, set, and add) are not |
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* supported. These methods throw |
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* <tt>UnsupportedOperationException</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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* @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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/** |
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* The held array. Directly accessed only within synchronized |
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* methods |
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*/ |
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private volatile transient E[] array; |
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|
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/** |
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* Accessor to the array intended to be called from |
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* within unsynchronized read-only methods |
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**/ |
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private E[] array() { return array; } |
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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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array = (E[]) 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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* @param c the collection of initially held elements |
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*/ |
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public CopyOnWriteArrayList(Collection<? extends E> c) { |
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array = (E[]) new Object[c.size()]; |
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Iterator<? extends E> i = c.iterator(); |
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int size = 0; |
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while (i.hasNext()) |
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array[size++] = i.next(); |
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} |
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|
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/** |
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* Create a new CopyOnWriteArrayList holding a copy of 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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**/ |
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public CopyOnWriteArrayList(E[] toCopyIn) { |
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copyIn(toCopyIn, 0, toCopyIn.length); |
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} |
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|
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/** |
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* Replace the held array with a copy of the <tt>n</tt> elements |
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* of the provided array, starting at position <tt>first</tt>. To |
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* copy an entire array, call with arguments (array, 0, |
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* array.length). |
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* @param toCopyIn the array. A copy of the indicated elements of |
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* this array is used as the internal array. |
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* @param first The index of first position of the array to |
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* start copying from. |
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* @param n the number of elements to copy. This will be the new size of |
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* the list. |
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**/ |
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private synchronized void copyIn(E[] toCopyIn, int first, int n) { |
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array = (E[]) new Object[n]; |
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System.arraycopy(toCopyIn, first, array, 0, n); |
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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 array().length; |
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} |
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|
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/** |
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* Tests if this list has no elements. |
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* |
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* @return <tt>true</tt> if this list has no elements; |
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* <tt>false</tt> otherwise. |
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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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* Returns <tt>true</tt> if this list contains the specified element. |
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* |
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* @param elem element whose presence in this List is to be tested. |
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* @return <code>true</code> if the specified element is present; |
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* <code>false</code> otherwise. |
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*/ |
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public boolean contains(Object elem) { |
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E[] elementData = array(); |
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int len = elementData.length; |
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return indexOf(elem, elementData, len) >= 0; |
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} |
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|
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/** |
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* Searches for the first occurrence of the given argument, testing |
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* for equality using the <tt>equals</tt> method. |
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* |
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* @param elem an object. |
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* @return the index of the first occurrence of the argument in this |
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* list; returns <tt>-1</tt> if the object is not found. |
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* @see Object#equals(Object) |
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*/ |
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public int indexOf(Object elem) { |
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E[] elementData = array(); |
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int len = elementData.length; |
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return indexOf(elem, elementData, len); |
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} |
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|
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/** |
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* static version allows repeated call without needed |
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* to grab lock for array each time |
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**/ |
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private static int indexOf(Object elem, Object[] elementData, int len) { |
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if (elem == null) { |
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for (int i = 0; i < len; i++) |
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if (elementData[i]==null) |
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return i; |
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} else { |
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for (int i = 0; i < len; i++) |
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if (elem.equals(elementData[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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* Searches for the first occurrence of the given argument, beginning |
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* the search at <tt>index</tt>, and testing for equality using |
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* the <tt>equals</tt> method. |
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* |
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* @param elem an object. |
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* @param index the index to start searching from. |
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* @return the index of the first occurrence of the object argument in |
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* this List at position <tt>index</tt> or later in the |
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* List; returns <tt>-1</tt> if the object is not found. |
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* @see Object#equals(Object) |
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*/ |
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public int indexOf(E elem, int index) { |
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E[] elementData = array(); |
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int elementCount = elementData.length; |
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|
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if (elem == null) { |
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for (int i = index ; i < elementCount ; i++) |
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if (elementData[i]==null) |
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return i; |
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} else { |
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for (int i = index ; i < elementCount ; i++) |
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if (elem.equals(elementData[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 the index of the last occurrence of the specified object in |
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* this list. |
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* |
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* @param elem the desired element. |
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* @return the index of the last occurrence of the specified object in |
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* this list; returns -1 if the object is not found. |
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*/ |
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public int lastIndexOf(Object elem) { |
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E[] elementData = array(); |
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int len = elementData.length; |
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return lastIndexOf(elem, elementData, len); |
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} |
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|
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private static int lastIndexOf(Object elem, Object[] elementData, int len) { |
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if (elem == null) { |
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for (int i = len-1; i >= 0; i--) |
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if (elementData[i]==null) |
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return i; |
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} else { |
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for (int i = len-1; i >= 0; i--) |
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if (elem.equals(elementData[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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* Searches backwards for the specified object, starting from the |
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* specified index, and returns an index to it. |
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* |
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* @param elem the desired element. |
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* @param index the index to start searching from. |
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* @return the index of the last occurrence of the specified object in this |
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* List at position less than index in the List; |
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* -1 if the object is not found. |
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*/ |
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public int lastIndexOf(E elem, int index) { |
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// needed in order to compile on 1.2b3 |
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E[] elementData = array(); |
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if (elem == null) { |
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for (int i = index; i >= 0; i--) |
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if (elementData[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 (elem.equals(elementData[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 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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E[] elementData = array(); |
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CopyOnWriteArrayList<E> v = (CopyOnWriteArrayList<E>)super.clone(); |
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v.array = (E[]) new Object[elementData.length]; |
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System.arraycopy(elementData, 0, v.array, 0, elementData.length); |
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return v; |
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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 the correct order. |
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* @return an array containing all of the elements in this list |
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* in the correct order. |
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*/ |
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public Object[] toArray() { |
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Object[] elementData = array(); |
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Object[] result = new Object[elementData.length]; |
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System.arraycopy(elementData, 0, result, 0, elementData.length); |
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return result; |
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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 in the |
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* correct order. The runtime type of the returned array is that of the |
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* specified array. If the list fits in the specified array, it is |
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* returned therein. Otherwise, a new array is allocated with the runtime |
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* type of the specified array and the size of this list. |
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* <p> |
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* If the list fits in the specified array with room to spare |
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* (i.e., the array has more elements than the list), |
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* the element in the array immediately following the end of the |
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* collection is set to null. This is useful in determining the length |
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* of the list <em>only</em> if the caller knows that the list |
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* does not contain any null elements. |
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* |
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* @param a the array into which the elements of the list are to |
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* be stored, if it is big enough; otherwise, a new array of the |
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* same runtime type is allocated for this purpose. |
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* @return an array containing the elements of the list. |
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* @throws ArrayStoreException if the runtime type of a is not a supertype |
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* of the runtime type of every element in this list. |
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*/ |
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public <T> T[] toArray(T a[]) { |
310 |
E[] elementData = array(); |
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|
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if (a.length < elementData.length) |
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a = (T[]) |
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java.lang.reflect.Array.newInstance(a.getClass().getComponentType(), |
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elementData.length); |
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|
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System.arraycopy(elementData, 0, a, 0, elementData.length); |
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|
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if (a.length > elementData.length) |
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a[elementData.length] = null; |
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|
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return a; |
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} |
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|
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// Positional Access Operations |
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|
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/** |
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* Returns the element at the specified position in this list. |
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* |
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* @param index index of element to return. |
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* @return the element at the specified position in this list. |
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* @throws IndexOutOfBoundsException if index is out of range <tt>(index |
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* < 0 || index >= size())</tt>. |
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*/ |
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public E get(int index) { |
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E[] elementData = array(); |
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rangeCheck(index, elementData.length); |
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return elementData[index]; |
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} |
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|
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/** |
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* Replaces the element at the specified position in this list with |
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* the specified element. |
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* |
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* @param index index of element to replace. |
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* @param element element to be stored at the specified position. |
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* @return the element previously at the specified position. |
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* @throws IndexOutOfBoundsException if index out of range |
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* <tt>(index < 0 || index >= size())</tt>. |
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*/ |
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public synchronized E set(int index, E element) { |
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int len = array.length; |
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rangeCheck(index, len); |
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E oldValue = array[index]; |
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|
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boolean same = (oldValue == element || |
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(element != null && element.equals(oldValue))); |
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if (!same) { |
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E[] newArray = (E[]) new Object[len]; |
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System.arraycopy(array, 0, newArray, 0, len); |
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newArray[index] = element; |
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array = newArray; |
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} |
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return oldValue; |
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} |
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|
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/** |
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* Appends the specified element to the end of this list. |
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* |
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* @param element element to be appended to this list. |
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* @return true (as per the general contract of Collection.add). |
372 |
*/ |
373 |
public synchronized boolean add(E element) { |
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int len = array.length; |
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E[] newArray = (E[]) new Object[len+1]; |
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System.arraycopy(array, 0, newArray, 0, len); |
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newArray[len] = element; |
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array = newArray; |
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return true; |
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} |
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|
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/** |
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* Inserts the specified element at the specified position in this |
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* list. Shifts the element currently at that position (if any) and |
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* any subsequent elements to the right (adds one to their indices). |
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* |
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* @param index index at which the specified element is to be inserted. |
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* @param element element to be inserted. |
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* @throws IndexOutOfBoundsException if index is out of range |
390 |
* <tt>(index < 0 || index > size())</tt>. |
391 |
*/ |
392 |
public synchronized void add(int index, E element) { |
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int len = array.length; |
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if (index > len || index < 0) |
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throw new IndexOutOfBoundsException("Index: "+index+", Size: "+len); |
396 |
|
397 |
E[] newArray = (E[]) new Object[len+1]; |
398 |
System.arraycopy(array, 0, newArray, 0, index); |
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newArray[index] = element; |
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System.arraycopy(array, index, newArray, index+1, len - index); |
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array = newArray; |
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} |
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|
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/** |
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* Removes the element at the specified position in this list. |
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* Shifts any subsequent elements to the left (subtracts one from their |
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* indices). |
408 |
* |
409 |
* @param index the index of the element to removed. |
410 |
* @return the element that was removed from the list. |
411 |
* @throws IndexOutOfBoundsException if index out of range <tt>(index |
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* < 0 || index >= size())</tt>. |
413 |
*/ |
414 |
public synchronized E remove(int index) { |
415 |
int len = array.length; |
416 |
rangeCheck(index, len); |
417 |
E oldValue = array[index]; |
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E[] newArray = (E[]) new Object[len-1]; |
419 |
System.arraycopy(array, 0, newArray, 0, index); |
420 |
int numMoved = len - index - 1; |
421 |
if (numMoved > 0) |
422 |
System.arraycopy(array, index+1, newArray, index, numMoved); |
423 |
array = newArray; |
424 |
return oldValue; |
425 |
} |
426 |
|
427 |
/** |
428 |
* Removes a single instance of the specified element from this |
429 |
* list, if it is present (optional operation). More formally, |
430 |
* removes an element <tt>e</tt> such that <tt>(o==null ? e==null : |
431 |
* o.equals(e))</tt>, if the list contains one or more such |
432 |
* elements. Returns <tt>true</tt> if the list contained the |
433 |
* specified element (or equivalently, if the list changed as a |
434 |
* result of the call).<p> |
435 |
* |
436 |
* @param o element to be removed from this list, if present. |
437 |
* @return <tt>true</tt> if the list contained the specified element. |
438 |
*/ |
439 |
public synchronized boolean remove(Object o) { |
440 |
int len = array.length; |
441 |
if (len == 0) return false; |
442 |
|
443 |
// Copy while searching for element to remove |
444 |
// This wins in the normal case of element being present |
445 |
|
446 |
int newlen = len-1; |
447 |
E[] newArray = (E[]) new Object[newlen]; |
448 |
|
449 |
for (int i = 0; i < newlen; ++i) { |
450 |
if (o == array[i] || |
451 |
(o != null && o.equals(array[i]))) { |
452 |
// found one; copy remaining and exit |
453 |
for (int k = i + 1; k < len; ++k) newArray[k-1] = array[k]; |
454 |
array = newArray; |
455 |
return true; |
456 |
} else |
457 |
newArray[i] = array[i]; |
458 |
} |
459 |
// special handling for last cell |
460 |
|
461 |
if (o == array[newlen] || |
462 |
(o != null && o.equals(array[newlen]))) { |
463 |
array = newArray; |
464 |
return true; |
465 |
} else |
466 |
return false; // throw away copy |
467 |
} |
468 |
|
469 |
|
470 |
/** |
471 |
* Removes from this List all of the elements whose index is between |
472 |
* fromIndex, inclusive and toIndex, exclusive. Shifts any succeeding |
473 |
* elements to the left (reduces their index). |
474 |
* This call shortens the list by <tt>(toIndex - fromIndex)</tt> elements. |
475 |
* (If <tt>toIndex==fromIndex</tt>, this operation has no effect.) |
476 |
* |
477 |
* @param fromIndex index of first element to be removed. |
478 |
* @param toIndex index after last element to be removed. |
479 |
* @throws IndexOutOfBoundsException if fromIndex or toIndex out of |
480 |
* range (fromIndex < 0 || fromIndex >= size() || toIndex |
481 |
* > size() || toIndex < fromIndex). |
482 |
*/ |
483 |
private synchronized void removeRange(int fromIndex, int toIndex) { |
484 |
int len = array.length; |
485 |
|
486 |
if (fromIndex < 0 || fromIndex >= len || |
487 |
toIndex > len || toIndex < fromIndex) |
488 |
throw new IndexOutOfBoundsException(); |
489 |
|
490 |
int numMoved = len - toIndex; |
491 |
int newlen = len - (toIndex-fromIndex); |
492 |
E[] newArray = (E[]) new Object[newlen]; |
493 |
System.arraycopy(array, 0, newArray, 0, fromIndex); |
494 |
System.arraycopy(array, toIndex, newArray, fromIndex, numMoved); |
495 |
array = newArray; |
496 |
} |
497 |
|
498 |
|
499 |
/** |
500 |
* Append the element if not present. |
501 |
* @param element element to be added to this Collection, if absent. |
502 |
* @return true if added |
503 |
**/ |
504 |
public synchronized boolean addIfAbsent(E element) { |
505 |
// Copy while checking if already present. |
506 |
// This wins in the most common case where it is not present |
507 |
int len = array.length; |
508 |
E[] newArray = (E[]) new Object[len + 1]; |
509 |
for (int i = 0; i < len; ++i) { |
510 |
if (element == array[i] || |
511 |
(element != null && element.equals(array[i]))) |
512 |
return false; // exit, throwing away copy |
513 |
else |
514 |
newArray[i] = array[i]; |
515 |
} |
516 |
newArray[len] = element; |
517 |
array = newArray; |
518 |
return true; |
519 |
} |
520 |
|
521 |
/** |
522 |
* Returns true if this Collection contains all of the elements in the |
523 |
* specified Collection. |
524 |
* <p> |
525 |
* This implementation iterates over the specified Collection, checking |
526 |
* each element returned by the Iterator in turn to see if it's |
527 |
* contained in this Collection. If all elements are so contained |
528 |
* true is returned, otherwise false. |
529 |
* @param c the collection |
530 |
* @return true if all elements are contained |
531 |
*/ |
532 |
public boolean containsAll(Collection<?> c) { |
533 |
E[] elementData = array(); |
534 |
int len = elementData.length; |
535 |
Iterator e = c.iterator(); |
536 |
while (e.hasNext()) |
537 |
if (indexOf(e.next(), elementData, len) < 0) |
538 |
return false; |
539 |
|
540 |
return true; |
541 |
} |
542 |
|
543 |
|
544 |
/** |
545 |
* Removes from this Collection all of its elements that are contained in |
546 |
* the specified Collection. This is a particularly expensive operation |
547 |
* in this class because of the need for an internal temporary array. |
548 |
* <p> |
549 |
* |
550 |
* @param c the collection |
551 |
* @return true if this Collection changed as a result of the call. |
552 |
*/ |
553 |
public synchronized boolean removeAll(Collection<?> c) { |
554 |
E[] elementData = array; |
555 |
int len = elementData.length; |
556 |
if (len == 0) return false; |
557 |
|
558 |
// temp array holds those elements we know we want to keep |
559 |
E[] temp = (E[]) new Object[len]; |
560 |
int newlen = 0; |
561 |
for (int i = 0; i < len; ++i) { |
562 |
E element = elementData[i]; |
563 |
if (!c.contains(element)) { |
564 |
temp[newlen++] = element; |
565 |
} |
566 |
} |
567 |
|
568 |
if (newlen == len) return false; |
569 |
|
570 |
// copy temp as new array |
571 |
E[] newArray = (E[]) new Object[newlen]; |
572 |
System.arraycopy(temp, 0, newArray, 0, newlen); |
573 |
array = newArray; |
574 |
return true; |
575 |
} |
576 |
|
577 |
/** |
578 |
* Retains only the elements in this Collection that are contained in the |
579 |
* specified Collection (optional operation). In other words, removes from |
580 |
* this Collection all of its elements that are not contained in the |
581 |
* specified Collection. |
582 |
* @param c the collection |
583 |
* @return true if this Collection changed as a result of the call. |
584 |
*/ |
585 |
public synchronized boolean retainAll(Collection<?> c) { |
586 |
E[] elementData = array; |
587 |
int len = elementData.length; |
588 |
if (len == 0) return false; |
589 |
|
590 |
E[] temp = (E[]) new Object[len]; |
591 |
int newlen = 0; |
592 |
for (int i = 0; i < len; ++i) { |
593 |
E element = elementData[i]; |
594 |
if (c.contains(element)) { |
595 |
temp[newlen++] = element; |
596 |
} |
597 |
} |
598 |
|
599 |
if (newlen == len) return false; |
600 |
|
601 |
E[] newArray = (E[]) new Object[newlen]; |
602 |
System.arraycopy(temp, 0, newArray, 0, newlen); |
603 |
array = newArray; |
604 |
return true; |
605 |
} |
606 |
|
607 |
/** |
608 |
* Appends all of the elements in the specified Collection that |
609 |
* are not already contained in this list, to the end of |
610 |
* this list, in the order that they are returned by the |
611 |
* specified Collection's Iterator. |
612 |
* |
613 |
* @param c elements to be added into this list. |
614 |
* @return the number of elements added |
615 |
*/ |
616 |
public synchronized int addAllAbsent(Collection<? extends E> c) { |
617 |
int numNew = c.size(); |
618 |
if (numNew == 0) return 0; |
619 |
|
620 |
E[] elementData = array; |
621 |
int len = elementData.length; |
622 |
|
623 |
E[] temp = (E[]) new Object[numNew]; |
624 |
int added = 0; |
625 |
Iterator<? extends E> e = c.iterator(); |
626 |
while (e.hasNext()) { |
627 |
E element = e.next(); |
628 |
if (indexOf(element, elementData, len) < 0) { |
629 |
if (indexOf(element, temp, added) < 0) { |
630 |
temp[added++] = element; |
631 |
} |
632 |
} |
633 |
} |
634 |
|
635 |
if (added == 0) return 0; |
636 |
|
637 |
E[] newArray = (E[]) new Object[len+added]; |
638 |
System.arraycopy(elementData, 0, newArray, 0, len); |
639 |
System.arraycopy(temp, 0, newArray, len, added); |
640 |
array = newArray; |
641 |
return added; |
642 |
} |
643 |
|
644 |
/** |
645 |
* Removes all of the elements from this list. |
646 |
* |
647 |
*/ |
648 |
public synchronized void clear() { |
649 |
array = (E[]) new Object[0]; |
650 |
} |
651 |
|
652 |
/** |
653 |
* Appends all of the elements in the specified Collection to the end of |
654 |
* this list, in the order that they are returned by the |
655 |
* specified Collection's Iterator. |
656 |
* |
657 |
* @param c elements to be inserted into this list. |
658 |
* @return true if any elements are added |
659 |
*/ |
660 |
public synchronized boolean addAll(Collection<? extends E> c) { |
661 |
int numNew = c.size(); |
662 |
if (numNew == 0) return false; |
663 |
|
664 |
int len = array.length; |
665 |
E[] newArray = (E[]) new Object[len+numNew]; |
666 |
System.arraycopy(array, 0, newArray, 0, len); |
667 |
Iterator<? extends E> e = c.iterator(); |
668 |
for (int i=0; i<numNew; i++) |
669 |
newArray[len++] = e.next(); |
670 |
array = newArray; |
671 |
|
672 |
return true; |
673 |
} |
674 |
|
675 |
/** |
676 |
* Inserts all of the elements in the specified Collection into this |
677 |
* list, starting at the specified position. Shifts the element |
678 |
* currently at that position (if any) and any subsequent elements to |
679 |
* the right (increases their indices). The new elements will appear |
680 |
* in the list in the order that they are returned by the |
681 |
* specified Collection's iterator. |
682 |
* |
683 |
* @param index index at which to insert first element |
684 |
* from the specified collection. |
685 |
* @param c elements to be inserted into this list. |
686 |
* @throws IndexOutOfBoundsException if index out of range (index |
687 |
* < 0 || index > size()). |
688 |
* @return true if any elements are added |
689 |
*/ |
690 |
public synchronized boolean addAll(int index, Collection<? extends E> c) { |
691 |
int len = array.length; |
692 |
if (index > len || index < 0) |
693 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: "+len); |
694 |
|
695 |
int numNew = c.size(); |
696 |
if (numNew == 0) return false; |
697 |
|
698 |
E[] newArray = (E[]) new Object[len+numNew]; |
699 |
System.arraycopy(array, 0, newArray, 0, len); |
700 |
int numMoved = len - index; |
701 |
if (numMoved > 0) |
702 |
System.arraycopy(array, index, newArray, index + numNew, numMoved); |
703 |
Iterator<? extends E> e = c.iterator(); |
704 |
for (int i=0; i<numNew; i++) |
705 |
newArray[index++] = e.next(); |
706 |
array = newArray; |
707 |
|
708 |
return true; |
709 |
} |
710 |
|
711 |
/** |
712 |
* Check if the given index is in range. If not, throw an appropriate |
713 |
* runtime exception. |
714 |
*/ |
715 |
private void rangeCheck(int index, int length) { |
716 |
if (index >= length || index < 0) |
717 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: "+ length); |
718 |
} |
719 |
|
720 |
/** |
721 |
* Save the state of the list to a stream (i.e., serialize it). |
722 |
* |
723 |
* @serialData The length of the array backing the list is emitted |
724 |
* (int), followed by all of its elements (each an Object) |
725 |
* in the proper order. |
726 |
* @param s the stream |
727 |
*/ |
728 |
private void writeObject(java.io.ObjectOutputStream s) |
729 |
throws java.io.IOException{ |
730 |
|
731 |
// Write out element count, and any hidden stuff |
732 |
s.defaultWriteObject(); |
733 |
|
734 |
E[] elementData = array(); |
735 |
// Write out array length |
736 |
s.writeInt(elementData.length); |
737 |
|
738 |
// Write out all elements in the proper order. |
739 |
for (int i=0; i<elementData.length; i++) |
740 |
s.writeObject(elementData[i]); |
741 |
} |
742 |
|
743 |
/** |
744 |
* Reconstitute the list from a stream (i.e., deserialize it). |
745 |
* @param s the stream |
746 |
*/ |
747 |
private void readObject(java.io.ObjectInputStream s) |
748 |
throws java.io.IOException, ClassNotFoundException { |
749 |
|
750 |
// Read in size, and any hidden stuff |
751 |
s.defaultReadObject(); |
752 |
|
753 |
// Read in array length and allocate array |
754 |
int arrayLength = s.readInt(); |
755 |
E[] elementData = (E[]) new Object[arrayLength]; |
756 |
|
757 |
// Read in all elements in the proper order. |
758 |
for (int i=0; i<elementData.length; i++) |
759 |
elementData[i] = (E) s.readObject(); |
760 |
array = elementData; |
761 |
} |
762 |
|
763 |
/** |
764 |
* Returns a string representation of this Collection, containing |
765 |
* the String representation of each element. |
766 |
*/ |
767 |
public String toString() { |
768 |
StringBuffer buf = new StringBuffer(); |
769 |
Iterator e = iterator(); |
770 |
buf.append("["); |
771 |
int maxIndex = size() - 1; |
772 |
for (int i = 0; i <= maxIndex; i++) { |
773 |
buf.append(String.valueOf(e.next())); |
774 |
if (i < maxIndex) |
775 |
buf.append(", "); |
776 |
} |
777 |
buf.append("]"); |
778 |
return buf.toString(); |
779 |
} |
780 |
|
781 |
|
782 |
/** |
783 |
* Compares the specified Object with this List for equality. Returns true |
784 |
* if and only if the specified Object is also a List, both Lists have the |
785 |
* same size, and all corresponding pairs of elements in the two Lists are |
786 |
* <em>equal</em>. (Two elements <tt>e1</tt> and <tt>e2</tt> are |
787 |
* <em>equal</em> if <tt>(e1==null ? e2==null : e1.equals(e2))</tt>.) |
788 |
* In other words, two Lists are defined to be equal if they contain the |
789 |
* same elements in the same order. |
790 |
* <p> |
791 |
* This implementation first checks if the specified object is this |
792 |
* List. If so, it returns true; if not, it checks if the specified |
793 |
* object is a List. If not, it returns false; if so, it iterates over |
794 |
* both lists, comparing corresponding pairs of elements. If any |
795 |
* comparison returns false, this method returns false. If either |
796 |
* Iterator runs out of elements before the other it returns false |
797 |
* (as the Lists are of unequal length); otherwise it returns true when |
798 |
* the iterations complete. |
799 |
* |
800 |
* @param o the Object to be compared for equality with this List. |
801 |
* @return true if the specified Object is equal to this List. |
802 |
*/ |
803 |
public boolean equals(Object o) { |
804 |
if (o == this) |
805 |
return true; |
806 |
if (!(o instanceof List)) |
807 |
return false; |
808 |
|
809 |
List<E> l2 = (List<E>)(o); |
810 |
if (size() != l2.size()) |
811 |
return false; |
812 |
|
813 |
ListIterator<E> e1 = listIterator(); |
814 |
ListIterator<E> e2 = l2.listIterator(); |
815 |
while(e1.hasNext()) { |
816 |
E o1 = e1.next(); |
817 |
E o2 = e2.next(); |
818 |
if (!(o1==null ? o2==null : o1.equals(o2))) |
819 |
return false; |
820 |
} |
821 |
return true; |
822 |
} |
823 |
|
824 |
/** |
825 |
* Returns the hash code value for this List. |
826 |
* |
827 |
* <p> This implementation uses the definition in {@link |
828 |
* List#hashCode}. |
829 |
* @return the hash code |
830 |
*/ |
831 |
public int hashCode() { |
832 |
int hashCode = 1; |
833 |
Iterator<E> i = iterator(); |
834 |
while (i.hasNext()) { |
835 |
E obj = i.next(); |
836 |
hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode()); |
837 |
} |
838 |
return hashCode; |
839 |
} |
840 |
|
841 |
/** |
842 |
* Returns an Iterator over the elements contained in this collection. |
843 |
* The iterator provides a snapshot of the state of the list |
844 |
* when the iterator was constructed. No synchronization is |
845 |
* needed while traversing the iterator. The iterator does |
846 |
* <em>NOT</em> support the <tt>remove</tt> method. |
847 |
* @return the iterator |
848 |
*/ |
849 |
public Iterator<E> iterator() { |
850 |
return new COWIterator<E>(array(), 0); |
851 |
} |
852 |
|
853 |
/** |
854 |
* Returns an Iterator of the elements in this List (in proper sequence). |
855 |
* The iterator provides a snapshot of the state of the list |
856 |
* when the iterator was constructed. No synchronization is |
857 |
* needed while traversing the iterator. The iterator does |
858 |
* <em>NOT</em> support the <tt>remove</tt>, <tt>set</tt>, |
859 |
* or <tt>add</tt> methods. |
860 |
* @return the iterator |
861 |
* |
862 |
*/ |
863 |
public ListIterator<E> listIterator() { |
864 |
return new COWIterator<E>(array(), 0); |
865 |
} |
866 |
|
867 |
/** |
868 |
* Returns a ListIterator of the elements in this List (in proper |
869 |
* sequence), starting at the specified position in the List. The |
870 |
* specified index indicates the first element that would be returned by |
871 |
* an initial call to nextElement. An initial call to previousElement |
872 |
* would return the element with the specified index minus one. |
873 |
* The ListIterator returned by this implementation will throw |
874 |
* an UnsupportedOperationException in its remove, set and |
875 |
* add methods. |
876 |
* |
877 |
* @param index index of first element to be returned from the |
878 |
* ListIterator (by a call to getNext). |
879 |
* @return the iterator |
880 |
* @throws IndexOutOfBoundsException if index is out of range |
881 |
* (index < 0 || index > size()). |
882 |
*/ |
883 |
public ListIterator<E> listIterator(final int index) { |
884 |
E[] elementData = array(); |
885 |
int len = elementData.length; |
886 |
if (index<0 || index>len) |
887 |
throw new IndexOutOfBoundsException("Index: "+index); |
888 |
|
889 |
return new COWIterator<E>(array(), index); |
890 |
} |
891 |
|
892 |
private static class COWIterator<E> implements ListIterator<E> { |
893 |
|
894 |
/** Snapshot of the array **/ |
895 |
private final E[] array; |
896 |
|
897 |
/** |
898 |
* Index of element to be returned by subsequent call to next. |
899 |
*/ |
900 |
private int cursor; |
901 |
|
902 |
private COWIterator(E[] elementArray, int initialCursor) { |
903 |
array = elementArray; |
904 |
cursor = initialCursor; |
905 |
} |
906 |
|
907 |
public boolean hasNext() { |
908 |
return cursor < array.length; |
909 |
} |
910 |
|
911 |
public boolean hasPrevious() { |
912 |
return cursor > 0; |
913 |
} |
914 |
|
915 |
public E next() { |
916 |
try { |
917 |
return array[cursor++]; |
918 |
} catch (IndexOutOfBoundsException ex) { |
919 |
throw new NoSuchElementException(); |
920 |
} |
921 |
} |
922 |
|
923 |
public E previous() { |
924 |
try { |
925 |
return array[--cursor]; |
926 |
} catch(IndexOutOfBoundsException e) { |
927 |
throw new NoSuchElementException(); |
928 |
} |
929 |
} |
930 |
|
931 |
public int nextIndex() { |
932 |
return cursor; |
933 |
} |
934 |
|
935 |
public int previousIndex() { |
936 |
return cursor-1; |
937 |
} |
938 |
|
939 |
/** |
940 |
* Not supported. Always throws UnsupportedOperationException. |
941 |
* @throws UnsupportedOperationException always; remove is not supported |
942 |
* by this Iterator. |
943 |
*/ |
944 |
|
945 |
public void remove() { |
946 |
throw new UnsupportedOperationException(); |
947 |
} |
948 |
|
949 |
/** |
950 |
* Not supported. Always throws UnsupportedOperationException. |
951 |
* @throws UnsupportedOperationException always; set is not supported |
952 |
* by this Iterator. |
953 |
*/ |
954 |
public void set(E o) { |
955 |
throw new UnsupportedOperationException(); |
956 |
} |
957 |
|
958 |
/** |
959 |
* Not supported. Always throws UnsupportedOperationException. |
960 |
* @throws UnsupportedOperationException always; add is not supported |
961 |
* by this Iterator. |
962 |
*/ |
963 |
public void add(E o) { |
964 |
throw new UnsupportedOperationException(); |
965 |
} |
966 |
} |
967 |
|
968 |
|
969 |
/** |
970 |
* Returns a view of the portion of this List between fromIndex, |
971 |
* inclusive, and toIndex, exclusive. The returned List is backed by this |
972 |
* List, so changes in the returned List are reflected in this List, and |
973 |
* vice-versa. While mutative operations are supported, they are |
974 |
* probably not very useful for CopyOnWriteArrayLists. |
975 |
* <p> |
976 |
* The semantics of the List returned by this method become undefined if |
977 |
* the backing list (i.e., this List) is <i>structurally modified</i> in |
978 |
* any way other than via the returned List. (Structural modifications are |
979 |
* those that change the size of the List, or otherwise perturb it in such |
980 |
* a fashion that iterations in progress may yield incorrect results.) |
981 |
* |
982 |
* @param fromIndex low endpoint (inclusive) of the subList. |
983 |
* @param toIndex high endpoint (exclusive) of the subList. |
984 |
* @return a view of the specified range within this List. |
985 |
* @throws IndexOutOfBoundsException if |
986 |
* (fromIndex < 0 || toIndex > size || fromIndex > toIndex). |
987 |
*/ |
988 |
public synchronized List<E> subList(int fromIndex, int toIndex) { |
989 |
// synchronized since sublist constructor depends on it. |
990 |
int len = array.length; |
991 |
if (fromIndex<0 || toIndex>len || fromIndex>toIndex) |
992 |
throw new IndexOutOfBoundsException(); |
993 |
return new COWSubList<E>(this, fromIndex, toIndex); |
994 |
} |
995 |
|
996 |
private static class COWSubList<E> extends AbstractList<E> { |
997 |
|
998 |
/* |
999 |
This class extends AbstractList merely for convenience, to |
1000 |
avoid having to define addAll, etc. This doesn't hurt, but |
1001 |
is wasteful. This class does not need or use modCount |
1002 |
mechanics in AbstractList, but does need to check for |
1003 |
concurrent modification using similar mechanics. On each |
1004 |
operation, the array that we expect the backing list to use |
1005 |
is checked and updated. Since we do this for all of the |
1006 |
base operations invoked by those defined in AbstractList, |
1007 |
all is well. While inefficient, this is not worth |
1008 |
improving. The kinds of list operations inherited from |
1009 |
AbstractList are already so slow on COW sublists that |
1010 |
adding a bit more space/time doesn't seem even noticeable. |
1011 |
*/ |
1012 |
|
1013 |
private final CopyOnWriteArrayList<E> l; |
1014 |
private final int offset; |
1015 |
private int size; |
1016 |
private E[] expectedArray; |
1017 |
|
1018 |
private COWSubList(CopyOnWriteArrayList<E> list, |
1019 |
int fromIndex, int toIndex) { |
1020 |
l = list; |
1021 |
expectedArray = l.array(); |
1022 |
offset = fromIndex; |
1023 |
size = toIndex - fromIndex; |
1024 |
} |
1025 |
|
1026 |
// only call this holding l's lock |
1027 |
private void checkForComodification() { |
1028 |
if (l.array != expectedArray) |
1029 |
throw new ConcurrentModificationException(); |
1030 |
} |
1031 |
|
1032 |
// only call this holding l's lock |
1033 |
private void rangeCheck(int index) { |
1034 |
if (index<0 || index>=size) |
1035 |
throw new IndexOutOfBoundsException("Index: "+index+ ",Size: "+size); |
1036 |
} |
1037 |
|
1038 |
|
1039 |
public E set(int index, E element) { |
1040 |
synchronized(l) { |
1041 |
rangeCheck(index); |
1042 |
checkForComodification(); |
1043 |
E x = l.set(index+offset, element); |
1044 |
expectedArray = l.array; |
1045 |
return x; |
1046 |
} |
1047 |
} |
1048 |
|
1049 |
public E get(int index) { |
1050 |
synchronized(l) { |
1051 |
rangeCheck(index); |
1052 |
checkForComodification(); |
1053 |
return l.get(index+offset); |
1054 |
} |
1055 |
} |
1056 |
|
1057 |
public int size() { |
1058 |
synchronized(l) { |
1059 |
checkForComodification(); |
1060 |
return size; |
1061 |
} |
1062 |
} |
1063 |
|
1064 |
public void add(int index, E element) { |
1065 |
synchronized(l) { |
1066 |
checkForComodification(); |
1067 |
if (index<0 || index>size) |
1068 |
throw new IndexOutOfBoundsException(); |
1069 |
l.add(index+offset, element); |
1070 |
expectedArray = l.array; |
1071 |
size++; |
1072 |
} |
1073 |
} |
1074 |
|
1075 |
public void clear() { |
1076 |
synchronized(l) { |
1077 |
checkForComodification(); |
1078 |
l.removeRange(offset, offset+size); |
1079 |
expectedArray = l.array; |
1080 |
size = 0; |
1081 |
} |
1082 |
} |
1083 |
|
1084 |
public E remove(int index) { |
1085 |
synchronized(l) { |
1086 |
rangeCheck(index); |
1087 |
checkForComodification(); |
1088 |
E result = l.remove(index+offset); |
1089 |
expectedArray = l.array; |
1090 |
size--; |
1091 |
return result; |
1092 |
} |
1093 |
} |
1094 |
|
1095 |
public Iterator<E> iterator() { |
1096 |
synchronized(l) { |
1097 |
checkForComodification(); |
1098 |
return new COWSubListIterator<E>(l, 0, offset, size); |
1099 |
} |
1100 |
} |
1101 |
|
1102 |
public ListIterator<E> listIterator(final int index) { |
1103 |
synchronized(l) { |
1104 |
checkForComodification(); |
1105 |
if (index<0 || index>size) |
1106 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: "+size); |
1107 |
return new COWSubListIterator<E>(l, index, offset, size); |
1108 |
} |
1109 |
} |
1110 |
|
1111 |
public List<E> subList(int fromIndex, int toIndex) { |
1112 |
synchronized(l) { |
1113 |
checkForComodification(); |
1114 |
if (fromIndex<0 || toIndex>size) |
1115 |
throw new IndexOutOfBoundsException(); |
1116 |
return new COWSubList<E>(l, fromIndex+offset, toIndex+offset); |
1117 |
} |
1118 |
} |
1119 |
|
1120 |
} |
1121 |
|
1122 |
|
1123 |
private static class COWSubListIterator<E> implements ListIterator<E> { |
1124 |
private final ListIterator<E> i; |
1125 |
private final int index; |
1126 |
private final int offset; |
1127 |
private final int size; |
1128 |
private COWSubListIterator(List<E> l, int index, int offset, int size) { |
1129 |
this.index = index; |
1130 |
this.offset = offset; |
1131 |
this.size = size; |
1132 |
i = l.listIterator(index+offset); |
1133 |
} |
1134 |
|
1135 |
public boolean hasNext() { |
1136 |
return nextIndex() < size; |
1137 |
} |
1138 |
|
1139 |
public E next() { |
1140 |
if (hasNext()) |
1141 |
return i.next(); |
1142 |
else |
1143 |
throw new NoSuchElementException(); |
1144 |
} |
1145 |
|
1146 |
public boolean hasPrevious() { |
1147 |
return previousIndex() >= 0; |
1148 |
} |
1149 |
|
1150 |
public E previous() { |
1151 |
if (hasPrevious()) |
1152 |
return i.previous(); |
1153 |
else |
1154 |
throw new NoSuchElementException(); |
1155 |
} |
1156 |
|
1157 |
public int nextIndex() { |
1158 |
return i.nextIndex() - offset; |
1159 |
} |
1160 |
|
1161 |
public int previousIndex() { |
1162 |
return i.previousIndex() - offset; |
1163 |
} |
1164 |
|
1165 |
public void remove() { |
1166 |
throw new UnsupportedOperationException(); |
1167 |
} |
1168 |
|
1169 |
public void set(E o) { |
1170 |
throw new UnsupportedOperationException(); |
1171 |
} |
1172 |
|
1173 |
public void add(E o) { |
1174 |
throw new UnsupportedOperationException(); |
1175 |
} |
1176 |
} |
1177 |
|
1178 |
} |