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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 (<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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* @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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* |
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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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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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* 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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copyIn(toCopyIn, 0, toCopyIn.length); |
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} |
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|
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/** |
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* Replaces 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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* 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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* 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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E[] elementData = array(); |
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int len = elementData.length; |
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return indexOf(o, elementData, len) >= 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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E[] elementData = array(); |
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int len = elementData.length; |
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return indexOf(o, elementData, len); |
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} |
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|
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/** |
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* static version allows repeated call without needing |
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* to grab lock for array each time |
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*/ |
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private static int indexOf(Object o, Object[] elementData, int len) { |
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if (o == 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 (o.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 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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E[] elementData = array(); |
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int elementCount = elementData.length; |
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|
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if (e == 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 (e.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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* {@inheritDoc} |
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*/ |
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public int lastIndexOf(Object o) { |
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E[] elementData = array(); |
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int len = elementData.length; |
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return lastIndexOf(o, elementData, len); |
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} |
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|
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private static int lastIndexOf(Object o, Object[] elementData, int len) { |
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if (o == 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 (o.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 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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// needed in order to compile on 1.2b3 |
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E[] elementData = array(); |
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if (e == 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 (e.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 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. |
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* |
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* @return an array containing all the elements in this list |
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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 |
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* proper sequence (from first to last element); the runtime type of |
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* 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 |
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* array is allocated with the runtime type of the specified array and |
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* the size of this list. |
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* |
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* <p>If this list fits in the specified array with room to spare |
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* (i.e., the array has more elements than this list), the element in |
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* the array immediately following the end of the list is set to |
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* <tt>null</tt>. (This is useful in determining the length of this |
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* list <i>only</i> if the caller knows that this list does not contain |
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* any null elements.) |
313 |
* |
314 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
315 |
* array-based and collection-based APIs. Further, this method allows |
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* precise control over the runtime type of the output array, and may, |
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* under certain circumstances, be used to save allocation costs. |
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* |
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* <p>Suppose <tt>x</tt> is a list known to contain only strings. |
320 |
* The following code can be used to dump the list into a newly |
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* allocated array of <tt>String</tt>: |
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* |
323 |
* <pre> |
324 |
* String[] y = x.toArray(new String[0]);</pre> |
325 |
* |
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* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
327 |
* <tt>toArray()</tt>. |
328 |
* |
329 |
* @param a the array into which the elements of the list are to |
330 |
* 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 all the elements in this list |
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* @throws ArrayStoreException if the runtime type of the specified array |
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* is not a supertype of the runtime type of every element in |
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* this list |
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* @throws NullPointerException if the specified array is null |
337 |
*/ |
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public <T> T[] toArray(T a[]) { |
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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; |
350 |
|
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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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* {@inheritDoc} |
358 |
* |
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* @throws IndexOutOfBoundsException {@inheritDoc} |
360 |
*/ |
361 |
public E get(int index) { |
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return array()[index]; |
363 |
} |
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|
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/** |
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* Replaces the element at the specified position in this list with the |
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* specified element. |
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* |
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* @throws IndexOutOfBoundsException {@inheritDoc} |
370 |
*/ |
371 |
public synchronized E set(int index, E element) { |
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int len = array.length; |
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E oldValue = array[index]; |
374 |
|
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boolean same = (oldValue == element || |
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(element != null && element.equals(oldValue))); |
377 |
if (!same) { |
378 |
E[] newArray = (E[]) new Object[len]; |
379 |
System.arraycopy(array, 0, newArray, 0, len); |
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newArray[index] = element; |
381 |
array = newArray; |
382 |
} |
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return oldValue; |
384 |
} |
385 |
|
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/** |
387 |
* Appends the specified element to the end of this list. |
388 |
* |
389 |
* @param element element to be appended to this list |
390 |
* @return <tt>true</tt> (as per the spec for {@link Collection#add}) |
391 |
*/ |
392 |
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). |
405 |
* |
406 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
407 |
*/ |
408 |
public synchronized void add(int index, E element) { |
409 |
int len = array.length; |
410 |
if (index > len || index < 0) |
411 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: "+len); |
412 |
|
413 |
E[] newArray = (E[]) new Object[len+1]; |
414 |
System.arraycopy(array, 0, newArray, 0, index); |
415 |
newArray[index] = element; |
416 |
System.arraycopy(array, index, newArray, index+1, len - index); |
417 |
array = newArray; |
418 |
} |
419 |
|
420 |
/** |
421 |
* Removes the element at the specified position in this list. |
422 |
* Shifts any subsequent elements to the left (subtracts one from their |
423 |
* indices). Returns the element that was removed from the list. |
424 |
* |
425 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
426 |
*/ |
427 |
public synchronized E remove(int index) { |
428 |
int len = array.length; |
429 |
E oldValue = array[index]; |
430 |
E[] newArray = (E[]) new Object[len-1]; |
431 |
System.arraycopy(array, 0, newArray, 0, index); |
432 |
int numMoved = len - index - 1; |
433 |
if (numMoved > 0) |
434 |
System.arraycopy(array, index+1, newArray, index, numMoved); |
435 |
array = newArray; |
436 |
return oldValue; |
437 |
} |
438 |
|
439 |
/** |
440 |
* Removes the first occurrence of the specified element from this list, |
441 |
* if it is present. If this list does not contain the element, it is |
442 |
* unchanged. More formally, removes the element with the lowest index |
443 |
* <tt>i</tt> such that |
444 |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> |
445 |
* (if such an element exists). Returns <tt>true</tt> if this list |
446 |
* contained the specified element (or equivalently, if this list |
447 |
* changed as a result of the call). |
448 |
* |
449 |
* @param o element to be removed from this list, if present |
450 |
* @return <tt>true</tt> if this list contained the specified element |
451 |
*/ |
452 |
public synchronized boolean remove(Object o) { |
453 |
int len = array.length; |
454 |
if (len == 0) return false; |
455 |
|
456 |
// Copy while searching for element to remove |
457 |
// This wins in the normal case of element being present |
458 |
|
459 |
int newlen = len-1; |
460 |
E[] newArray = (E[]) new Object[newlen]; |
461 |
|
462 |
for (int i = 0; i < newlen; ++i) { |
463 |
if (o == array[i] || |
464 |
(o != null && o.equals(array[i]))) { |
465 |
// found one; copy remaining and exit |
466 |
for (int k = i + 1; k < len; ++k) newArray[k-1] = array[k]; |
467 |
array = newArray; |
468 |
return true; |
469 |
} else |
470 |
newArray[i] = array[i]; |
471 |
} |
472 |
// special handling for last cell |
473 |
|
474 |
if (o == array[newlen] || |
475 |
(o != null && o.equals(array[newlen]))) { |
476 |
array = newArray; |
477 |
return true; |
478 |
} else |
479 |
return false; // throw away copy |
480 |
} |
481 |
|
482 |
/** |
483 |
* Removes from this list all of the elements whose index is between |
484 |
* <tt>fromIndex</tt>, inclusive, and <tt>toIndex</tt>, exclusive. |
485 |
* Shifts any succeeding elements to the left (reduces their index). |
486 |
* This call shortens the list by <tt>(toIndex - fromIndex)</tt> elements. |
487 |
* (If <tt>toIndex==fromIndex</tt>, this operation has no effect.) |
488 |
* |
489 |
* @param fromIndex index of first element to be removed |
490 |
* @param toIndex index after last element to be removed |
491 |
* @throws IndexOutOfBoundsException if fromIndex or toIndex out of |
492 |
* range (fromIndex < 0 || fromIndex >= size() || toIndex |
493 |
* > size() || toIndex < fromIndex) |
494 |
*/ |
495 |
private synchronized void removeRange(int fromIndex, int toIndex) { |
496 |
int len = array.length; |
497 |
|
498 |
if (fromIndex < 0 || fromIndex >= len || |
499 |
toIndex > len || toIndex < fromIndex) |
500 |
throw new IndexOutOfBoundsException(); |
501 |
|
502 |
int numMoved = len - toIndex; |
503 |
int newlen = len - (toIndex-fromIndex); |
504 |
E[] newArray = (E[]) new Object[newlen]; |
505 |
System.arraycopy(array, 0, newArray, 0, fromIndex); |
506 |
System.arraycopy(array, toIndex, newArray, fromIndex, numMoved); |
507 |
array = newArray; |
508 |
} |
509 |
|
510 |
/** |
511 |
* Append the element if not present. |
512 |
* |
513 |
* @param element element to be added to this list, if absent |
514 |
* @return <tt>true</tt> if the element was added |
515 |
*/ |
516 |
public synchronized boolean addIfAbsent(E element) { |
517 |
// Copy while checking if already present. |
518 |
// This wins in the most common case where it is not present |
519 |
int len = array.length; |
520 |
E[] newArray = (E[]) new Object[len + 1]; |
521 |
for (int i = 0; i < len; ++i) { |
522 |
if (element == array[i] || |
523 |
(element != null && element.equals(array[i]))) |
524 |
return false; // exit, throwing away copy |
525 |
else |
526 |
newArray[i] = array[i]; |
527 |
} |
528 |
newArray[len] = element; |
529 |
array = newArray; |
530 |
return true; |
531 |
} |
532 |
|
533 |
/** |
534 |
* Returns <tt>true</tt> if this list contains all of the elements of the |
535 |
* specified collection. |
536 |
* |
537 |
* @param c collection to be checked for containment in this list |
538 |
* @return <tt>true</tt> if this list contains all of the elements of the |
539 |
* specified collection |
540 |
* @throws NullPointerException if the specified collection is null |
541 |
* @see #contains(Object) |
542 |
*/ |
543 |
public boolean containsAll(Collection<?> c) { |
544 |
E[] elementData = array(); |
545 |
int len = elementData.length; |
546 |
Iterator e = c.iterator(); |
547 |
while (e.hasNext()) |
548 |
if (indexOf(e.next(), elementData, len) < 0) |
549 |
return false; |
550 |
|
551 |
return true; |
552 |
} |
553 |
|
554 |
/** |
555 |
* Removes from this list all of its elements that are contained in |
556 |
* the specified collection. This is a particularly expensive operation |
557 |
* in this class because of the need for an internal temporary array. |
558 |
* |
559 |
* @param c collection containing elements to be removed from this list |
560 |
* @return <tt>true</tt> if this list changed as a result of the call |
561 |
* @throws ClassCastException if the class of an element of this list |
562 |
* is incompatible with the specified collection (optional) |
563 |
* @throws NullPointerException if this list contains a null element and the |
564 |
* specified collection does not permit null elements (optional), |
565 |
* or if the specified collection is null |
566 |
* @see #remove(Object) |
567 |
*/ |
568 |
public synchronized boolean removeAll(Collection<?> c) { |
569 |
E[] elementData = array; |
570 |
int len = elementData.length; |
571 |
if (len == 0) return false; |
572 |
|
573 |
// temp array holds those elements we know we want to keep |
574 |
E[] temp = (E[]) new Object[len]; |
575 |
int newlen = 0; |
576 |
for (int i = 0; i < len; ++i) { |
577 |
E element = elementData[i]; |
578 |
if (!c.contains(element)) { |
579 |
temp[newlen++] = element; |
580 |
} |
581 |
} |
582 |
|
583 |
if (newlen == len) return false; |
584 |
|
585 |
// copy temp as new array |
586 |
E[] newArray = (E[]) new Object[newlen]; |
587 |
System.arraycopy(temp, 0, newArray, 0, newlen); |
588 |
array = newArray; |
589 |
return true; |
590 |
} |
591 |
|
592 |
/** |
593 |
* Retains only the elements in this list that are contained in the |
594 |
* specified collection. In other words, removes from this list all of |
595 |
* its elements that are not contained in the specified collection. |
596 |
* |
597 |
* @param c collection containing elements to be retained in this list |
598 |
* @return <tt>true</tt> if this list changed as a result of the call |
599 |
* @throws ClassCastException if the class of an element of this list |
600 |
* is incompatible with the specified collection (optional) |
601 |
* @throws NullPointerException if this list contains a null element and the |
602 |
* specified collection does not permit null elements (optional), |
603 |
* or if the specified collection is null |
604 |
* @see #remove(Object) |
605 |
*/ |
606 |
public synchronized boolean retainAll(Collection<?> c) { |
607 |
E[] elementData = array; |
608 |
int len = elementData.length; |
609 |
if (len == 0) return false; |
610 |
|
611 |
E[] temp = (E[]) new Object[len]; |
612 |
int newlen = 0; |
613 |
for (int i = 0; i < len; ++i) { |
614 |
E element = elementData[i]; |
615 |
if (c.contains(element)) { |
616 |
temp[newlen++] = element; |
617 |
} |
618 |
} |
619 |
|
620 |
if (newlen == len) return false; |
621 |
|
622 |
E[] newArray = (E[]) new Object[newlen]; |
623 |
System.arraycopy(temp, 0, newArray, 0, newlen); |
624 |
array = newArray; |
625 |
return true; |
626 |
} |
627 |
|
628 |
/** |
629 |
* Appends all of the elements in the specified collection that |
630 |
* are not already contained in this list, to the end of |
631 |
* this list, in the order that they are returned by the |
632 |
* specified collection's iterator. |
633 |
* |
634 |
* @param c collection containing elements to be added to this list |
635 |
* @return the number of elements added |
636 |
* @throws NullPointerException if the specified collection is null |
637 |
* @see #addIfAbsent(Object) |
638 |
*/ |
639 |
public synchronized int addAllAbsent(Collection<? extends E> c) { |
640 |
int numNew = c.size(); |
641 |
if (numNew == 0) return 0; |
642 |
|
643 |
E[] elementData = array; |
644 |
int len = elementData.length; |
645 |
|
646 |
E[] temp = (E[]) new Object[numNew]; |
647 |
int added = 0; |
648 |
Iterator<? extends E> e = c.iterator(); |
649 |
while (e.hasNext()) { |
650 |
E element = e.next(); |
651 |
if (indexOf(element, elementData, len) < 0) { |
652 |
if (indexOf(element, temp, added) < 0) { |
653 |
temp[added++] = element; |
654 |
} |
655 |
} |
656 |
} |
657 |
|
658 |
if (added == 0) return 0; |
659 |
|
660 |
E[] newArray = (E[]) new Object[len+added]; |
661 |
System.arraycopy(elementData, 0, newArray, 0, len); |
662 |
System.arraycopy(temp, 0, newArray, len, added); |
663 |
array = newArray; |
664 |
return added; |
665 |
} |
666 |
|
667 |
/** |
668 |
* Removes all of the elements from this list. |
669 |
* The list will be empty after this call returns. |
670 |
*/ |
671 |
public synchronized void clear() { |
672 |
array = (E[]) new Object[0]; |
673 |
} |
674 |
|
675 |
/** |
676 |
* Appends all of the elements in the specified collection to the end |
677 |
* of this list, in the order that they are returned by the specified |
678 |
* collection's iterator. |
679 |
* |
680 |
* @param c collection containing elements to be added to this list |
681 |
* @return <tt>true</tt> if this list changed as a result of the call |
682 |
* @throws NullPointerException if the specified collection is null |
683 |
* @see #add(Object) |
684 |
*/ |
685 |
public synchronized boolean addAll(Collection<? extends E> c) { |
686 |
int numNew = c.size(); |
687 |
if (numNew == 0) return false; |
688 |
|
689 |
int len = array.length; |
690 |
E[] newArray = (E[]) new Object[len+numNew]; |
691 |
System.arraycopy(array, 0, newArray, 0, len); |
692 |
Iterator<? extends E> e = c.iterator(); |
693 |
for (int i=0; i<numNew; i++) |
694 |
newArray[len++] = e.next(); |
695 |
array = newArray; |
696 |
|
697 |
return true; |
698 |
} |
699 |
|
700 |
/** |
701 |
* Inserts all of the elements in the specified collection into this |
702 |
* list, starting at the specified position. Shifts the element |
703 |
* currently at that position (if any) and any subsequent elements to |
704 |
* the right (increases their indices). The new elements will appear |
705 |
* in this list in the order that they are returned by the |
706 |
* specified collection's iterator. |
707 |
* |
708 |
* @param index index at which to insert the first element |
709 |
* from the specified collection |
710 |
* @param c collection containing elements to be added to this list |
711 |
* @return <tt>true</tt> if this list changed as a result of the call |
712 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
713 |
* @throws NullPointerException if the specified collection is null |
714 |
* @see #add(int,Object) |
715 |
*/ |
716 |
public synchronized boolean addAll(int index, Collection<? extends E> c) { |
717 |
int len = array.length; |
718 |
if (index > len || index < 0) |
719 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: "+len); |
720 |
|
721 |
int numNew = c.size(); |
722 |
if (numNew == 0) return false; |
723 |
|
724 |
E[] newArray = (E[]) new Object[len+numNew]; |
725 |
System.arraycopy(array, 0, newArray, 0, len); |
726 |
int numMoved = len - index; |
727 |
if (numMoved > 0) |
728 |
System.arraycopy(array, index, newArray, index + numNew, numMoved); |
729 |
Iterator<? extends E> e = c.iterator(); |
730 |
for (int i=0; i<numNew; i++) |
731 |
newArray[index++] = e.next(); |
732 |
array = newArray; |
733 |
|
734 |
return true; |
735 |
} |
736 |
|
737 |
/** |
738 |
* Checks if the given index is in range. If not, throws an appropriate |
739 |
* runtime exception. |
740 |
*/ |
741 |
private void rangeCheck(int index, int length) { |
742 |
if (index >= length || index < 0) |
743 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: "+ length); |
744 |
} |
745 |
|
746 |
/** |
747 |
* Save the state of the list to a stream (i.e., serialize it). |
748 |
* |
749 |
* @serialData The length of the array backing the list is emitted |
750 |
* (int), followed by all of its elements (each an Object) |
751 |
* in the proper order. |
752 |
* @param s the stream |
753 |
*/ |
754 |
private void writeObject(java.io.ObjectOutputStream s) |
755 |
throws java.io.IOException{ |
756 |
|
757 |
// Write out element count, and any hidden stuff |
758 |
s.defaultWriteObject(); |
759 |
|
760 |
E[] elementData = array(); |
761 |
// Write out array length |
762 |
s.writeInt(elementData.length); |
763 |
|
764 |
// Write out all elements in the proper order. |
765 |
for (int i=0; i<elementData.length; i++) |
766 |
s.writeObject(elementData[i]); |
767 |
} |
768 |
|
769 |
/** |
770 |
* Reconstitute the list from a stream (i.e., deserialize it). |
771 |
* @param s the stream |
772 |
*/ |
773 |
private void readObject(java.io.ObjectInputStream s) |
774 |
throws java.io.IOException, ClassNotFoundException { |
775 |
|
776 |
// Read in size, and any hidden stuff |
777 |
s.defaultReadObject(); |
778 |
|
779 |
// Read in array length and allocate array |
780 |
int arrayLength = s.readInt(); |
781 |
E[] elementData = (E[]) new Object[arrayLength]; |
782 |
|
783 |
// Read in all elements in the proper order. |
784 |
for (int i=0; i<elementData.length; i++) |
785 |
elementData[i] = (E) s.readObject(); |
786 |
array = elementData; |
787 |
} |
788 |
|
789 |
/** |
790 |
* Returns a string representation of this list, containing |
791 |
* the String representation of each element. |
792 |
*/ |
793 |
public String toString() { |
794 |
StringBuffer buf = new StringBuffer(); |
795 |
Iterator e = iterator(); |
796 |
buf.append("["); |
797 |
int maxIndex = size() - 1; |
798 |
for (int i = 0; i <= maxIndex; i++) { |
799 |
buf.append(String.valueOf(e.next())); |
800 |
if (i < maxIndex) |
801 |
buf.append(", "); |
802 |
} |
803 |
buf.append("]"); |
804 |
return buf.toString(); |
805 |
} |
806 |
|
807 |
/** |
808 |
* Compares the specified object with this list for equality. |
809 |
* Returns true if and only if the specified object is also a {@link |
810 |
* List}, both lists have the same size, and all corresponding pairs |
811 |
* of elements in the two lists are <em>equal</em>. (Two elements |
812 |
* <tt>e1</tt> and <tt>e2</tt> are <em>equal</em> if <tt>(e1==null ? |
813 |
* e2==null : e1.equals(e2))</tt>.) In other words, two lists are |
814 |
* defined to be equal if they contain the same elements in the same |
815 |
* order. |
816 |
* |
817 |
* @param o the object to be compared for equality with this list |
818 |
* @return <tt>true</tt> if the specified object is equal to this list |
819 |
*/ |
820 |
public boolean equals(Object o) { |
821 |
if (o == this) |
822 |
return true; |
823 |
if (!(o instanceof List)) |
824 |
return false; |
825 |
|
826 |
List<E> l2 = (List<E>)(o); |
827 |
if (size() != l2.size()) |
828 |
return false; |
829 |
|
830 |
ListIterator<E> e1 = listIterator(); |
831 |
ListIterator<E> e2 = l2.listIterator(); |
832 |
while (e1.hasNext()) { |
833 |
E o1 = e1.next(); |
834 |
E o2 = e2.next(); |
835 |
if (!(o1==null ? o2==null : o1.equals(o2))) |
836 |
return false; |
837 |
} |
838 |
return true; |
839 |
} |
840 |
|
841 |
/** |
842 |
* Returns the hash code value for this list. |
843 |
* |
844 |
* <p> This implementation uses the definition in {@link |
845 |
* List#hashCode}. |
846 |
* @return the hash code |
847 |
*/ |
848 |
public int hashCode() { |
849 |
int hashCode = 1; |
850 |
Iterator<E> i = iterator(); |
851 |
while (i.hasNext()) { |
852 |
E obj = i.next(); |
853 |
hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode()); |
854 |
} |
855 |
return hashCode; |
856 |
} |
857 |
|
858 |
/** |
859 |
* Returns an iterator over the elements in this list in proper sequence. |
860 |
* |
861 |
* <p>The returned iterator provides a snapshot of the state of the list |
862 |
* when the iterator was constructed. No synchronization is needed while |
863 |
* traversing the iterator. The iterator does <em>NOT</em> support the |
864 |
* <tt>remove</tt> method. |
865 |
* |
866 |
* @return an iterator over the elements in this list in proper sequence |
867 |
*/ |
868 |
public Iterator<E> iterator() { |
869 |
return new COWIterator<E>(array(), 0); |
870 |
} |
871 |
|
872 |
/** |
873 |
* {@inheritDoc} |
874 |
* |
875 |
* <p>The returned iterator provides a snapshot of the state of the list |
876 |
* when the iterator was constructed. No synchronization is needed while |
877 |
* traversing the iterator. The iterator does <em>NOT</em> support the |
878 |
* <tt>remove</tt>, <tt>set</tt> or <tt>add</tt> methods. |
879 |
*/ |
880 |
public ListIterator<E> listIterator() { |
881 |
return new COWIterator<E>(array(), 0); |
882 |
} |
883 |
|
884 |
/** |
885 |
* {@inheritDoc} |
886 |
* |
887 |
* <p>The list iterator returned by this implementation will throw an |
888 |
* <tt>UnsupportedOperationException</tt> in its <tt>remove</tt>, |
889 |
* <tt>set</tt> and <tt>add</tt> methods. |
890 |
* |
891 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
892 |
*/ |
893 |
public ListIterator<E> listIterator(final int index) { |
894 |
E[] elementData = array(); |
895 |
int len = elementData.length; |
896 |
if (index<0 || index>len) |
897 |
throw new IndexOutOfBoundsException("Index: "+index); |
898 |
|
899 |
return new COWIterator<E>(array(), index); |
900 |
} |
901 |
|
902 |
private static class COWIterator<E> implements ListIterator<E> { |
903 |
|
904 |
/** Snapshot of the array **/ |
905 |
private final E[] array; |
906 |
|
907 |
/** |
908 |
* Index of element to be returned by subsequent call to next. |
909 |
*/ |
910 |
private int cursor; |
911 |
|
912 |
private COWIterator(E[] elementArray, int initialCursor) { |
913 |
array = elementArray; |
914 |
cursor = initialCursor; |
915 |
} |
916 |
|
917 |
public boolean hasNext() { |
918 |
return cursor < array.length; |
919 |
} |
920 |
|
921 |
public boolean hasPrevious() { |
922 |
return cursor > 0; |
923 |
} |
924 |
|
925 |
public E next() { |
926 |
try { |
927 |
return array[cursor++]; |
928 |
} catch (IndexOutOfBoundsException ex) { |
929 |
throw new NoSuchElementException(); |
930 |
} |
931 |
} |
932 |
|
933 |
public E previous() { |
934 |
try { |
935 |
return array[--cursor]; |
936 |
} catch (IndexOutOfBoundsException e) { |
937 |
throw new NoSuchElementException(); |
938 |
} |
939 |
} |
940 |
|
941 |
public int nextIndex() { |
942 |
return cursor; |
943 |
} |
944 |
|
945 |
public int previousIndex() { |
946 |
return cursor-1; |
947 |
} |
948 |
|
949 |
/** |
950 |
* Not supported. Always throws UnsupportedOperationException. |
951 |
* @throws UnsupportedOperationException always; <tt>remove</tt> |
952 |
* is not supported by this iterator. |
953 |
*/ |
954 |
public void remove() { |
955 |
throw new UnsupportedOperationException(); |
956 |
} |
957 |
|
958 |
/** |
959 |
* Not supported. Always throws UnsupportedOperationException. |
960 |
* @throws UnsupportedOperationException always; <tt>set</tt> |
961 |
* is not supported by this iterator. |
962 |
*/ |
963 |
public void set(E e) { |
964 |
throw new UnsupportedOperationException(); |
965 |
} |
966 |
|
967 |
/** |
968 |
* Not supported. Always throws UnsupportedOperationException. |
969 |
* @throws UnsupportedOperationException always; <tt>add</tt> |
970 |
* is not supported by this iterator. |
971 |
*/ |
972 |
public void add(E e) { |
973 |
throw new UnsupportedOperationException(); |
974 |
} |
975 |
} |
976 |
|
977 |
/** |
978 |
* Returns a view of the portion of this list between <tt>fromIndex</tt>, |
979 |
* inclusive, and <tt>toIndex</tt>, exclusive. The returned list is |
980 |
* backed by this list, so changes in the returned list are reflected in |
981 |
* this list, and vice-versa. While mutative operations are supported, |
982 |
* they are probably not very useful for CopyOnWriteArrayLists. |
983 |
* |
984 |
* <p>The semantics of the list returned by this method become undefined if |
985 |
* the backing list (i.e., this list) is <i>structurally modified</i> in |
986 |
* any way other than via the returned list. (Structural modifications are |
987 |
* those that change the size of the list, or otherwise perturb it in such |
988 |
* a fashion that iterations in progress may yield incorrect results.) |
989 |
* |
990 |
* @param fromIndex low endpoint (inclusive) of the subList |
991 |
* @param toIndex high endpoint (exclusive) of the subList |
992 |
* @return a view of the specified range within this list |
993 |
* @throws IndexOutOfBoundsException {@inheritDoc} |
994 |
*/ |
995 |
public synchronized List<E> subList(int fromIndex, int toIndex) { |
996 |
// synchronized since sublist constructor depends on it. |
997 |
int len = array.length; |
998 |
if (fromIndex<0 || toIndex>len || fromIndex>toIndex) |
999 |
throw new IndexOutOfBoundsException(); |
1000 |
return new COWSubList<E>(this, fromIndex, toIndex); |
1001 |
} |
1002 |
|
1003 |
private static class COWSubList<E> extends AbstractList<E> { |
1004 |
|
1005 |
/* |
1006 |
This class extends AbstractList merely for convenience, to |
1007 |
avoid having to define addAll, etc. This doesn't hurt, but |
1008 |
is wasteful. This class does not need or use modCount |
1009 |
mechanics in AbstractList, but does need to check for |
1010 |
concurrent modification using similar mechanics. On each |
1011 |
operation, the array that we expect the backing list to use |
1012 |
is checked and updated. Since we do this for all of the |
1013 |
base operations invoked by those defined in AbstractList, |
1014 |
all is well. While inefficient, this is not worth |
1015 |
improving. The kinds of list operations inherited from |
1016 |
AbstractList are already so slow on COW sublists that |
1017 |
adding a bit more space/time doesn't seem even noticeable. |
1018 |
*/ |
1019 |
|
1020 |
private final CopyOnWriteArrayList<E> l; |
1021 |
private final int offset; |
1022 |
private int size; |
1023 |
private E[] expectedArray; |
1024 |
|
1025 |
private COWSubList(CopyOnWriteArrayList<E> list, |
1026 |
int fromIndex, int toIndex) { |
1027 |
l = list; |
1028 |
expectedArray = l.array(); |
1029 |
offset = fromIndex; |
1030 |
size = toIndex - fromIndex; |
1031 |
} |
1032 |
|
1033 |
// only call this holding l's lock |
1034 |
private void checkForComodification() { |
1035 |
if (l.array != expectedArray) |
1036 |
throw new ConcurrentModificationException(); |
1037 |
} |
1038 |
|
1039 |
// only call this holding l's lock |
1040 |
private void rangeCheck(int index) { |
1041 |
if (index<0 || index>=size) |
1042 |
throw new IndexOutOfBoundsException("Index: "+index+ ",Size: "+size); |
1043 |
} |
1044 |
|
1045 |
|
1046 |
public E set(int index, E element) { |
1047 |
synchronized(l) { |
1048 |
rangeCheck(index); |
1049 |
checkForComodification(); |
1050 |
E x = l.set(index+offset, element); |
1051 |
expectedArray = l.array; |
1052 |
return x; |
1053 |
} |
1054 |
} |
1055 |
|
1056 |
public E get(int index) { |
1057 |
synchronized(l) { |
1058 |
rangeCheck(index); |
1059 |
checkForComodification(); |
1060 |
return l.get(index+offset); |
1061 |
} |
1062 |
} |
1063 |
|
1064 |
public int size() { |
1065 |
synchronized(l) { |
1066 |
checkForComodification(); |
1067 |
return size; |
1068 |
} |
1069 |
} |
1070 |
|
1071 |
public void add(int index, E element) { |
1072 |
synchronized(l) { |
1073 |
checkForComodification(); |
1074 |
if (index<0 || index>size) |
1075 |
throw new IndexOutOfBoundsException(); |
1076 |
l.add(index+offset, element); |
1077 |
expectedArray = l.array; |
1078 |
size++; |
1079 |
} |
1080 |
} |
1081 |
|
1082 |
public void clear() { |
1083 |
synchronized(l) { |
1084 |
checkForComodification(); |
1085 |
l.removeRange(offset, offset+size); |
1086 |
expectedArray = l.array; |
1087 |
size = 0; |
1088 |
} |
1089 |
} |
1090 |
|
1091 |
public E remove(int index) { |
1092 |
synchronized(l) { |
1093 |
rangeCheck(index); |
1094 |
checkForComodification(); |
1095 |
E result = l.remove(index+offset); |
1096 |
expectedArray = l.array; |
1097 |
size--; |
1098 |
return result; |
1099 |
} |
1100 |
} |
1101 |
|
1102 |
public Iterator<E> iterator() { |
1103 |
synchronized(l) { |
1104 |
checkForComodification(); |
1105 |
return new COWSubListIterator<E>(l, 0, offset, size); |
1106 |
} |
1107 |
} |
1108 |
|
1109 |
public ListIterator<E> listIterator(final int index) { |
1110 |
synchronized(l) { |
1111 |
checkForComodification(); |
1112 |
if (index<0 || index>size) |
1113 |
throw new IndexOutOfBoundsException("Index: "+index+", Size: "+size); |
1114 |
return new COWSubListIterator<E>(l, index, offset, size); |
1115 |
} |
1116 |
} |
1117 |
|
1118 |
public List<E> subList(int fromIndex, int toIndex) { |
1119 |
synchronized(l) { |
1120 |
checkForComodification(); |
1121 |
if (fromIndex<0 || toIndex>size) |
1122 |
throw new IndexOutOfBoundsException(); |
1123 |
return new COWSubList<E>(l, fromIndex+offset, toIndex+offset); |
1124 |
} |
1125 |
} |
1126 |
|
1127 |
} |
1128 |
|
1129 |
|
1130 |
private static class COWSubListIterator<E> implements ListIterator<E> { |
1131 |
private final ListIterator<E> i; |
1132 |
private final int index; |
1133 |
private final int offset; |
1134 |
private final int size; |
1135 |
private COWSubListIterator(List<E> l, int index, int offset, int size) { |
1136 |
this.index = index; |
1137 |
this.offset = offset; |
1138 |
this.size = size; |
1139 |
i = l.listIterator(index+offset); |
1140 |
} |
1141 |
|
1142 |
public boolean hasNext() { |
1143 |
return nextIndex() < size; |
1144 |
} |
1145 |
|
1146 |
public E next() { |
1147 |
if (hasNext()) |
1148 |
return i.next(); |
1149 |
else |
1150 |
throw new NoSuchElementException(); |
1151 |
} |
1152 |
|
1153 |
public boolean hasPrevious() { |
1154 |
return previousIndex() >= 0; |
1155 |
} |
1156 |
|
1157 |
public E previous() { |
1158 |
if (hasPrevious()) |
1159 |
return i.previous(); |
1160 |
else |
1161 |
throw new NoSuchElementException(); |
1162 |
} |
1163 |
|
1164 |
public int nextIndex() { |
1165 |
return i.nextIndex() - offset; |
1166 |
} |
1167 |
|
1168 |
public int previousIndex() { |
1169 |
return i.previousIndex() - offset; |
1170 |
} |
1171 |
|
1172 |
public void remove() { |
1173 |
throw new UnsupportedOperationException(); |
1174 |
} |
1175 |
|
1176 |
public void set(E e) { |
1177 |
throw new UnsupportedOperationException(); |
1178 |
} |
1179 |
|
1180 |
public void add(E e) { |
1181 |
throw new UnsupportedOperationException(); |
1182 |
} |
1183 |
} |
1184 |
|
1185 |
} |