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/* |
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* %W% %E% |
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* |
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* Copyright 2005 Sun Microsystems, Inc. All rights reserved. |
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* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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*/ |
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|
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package java.util; |
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|
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/** |
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* Linked list implementation of the <tt>List</tt> interface. Implements all |
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* optional list operations, and permits all elements (including |
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* <tt>null</tt>). In addition to implementing the <tt>List</tt> interface, |
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* the <tt>LinkedList</tt> class provides uniformly named methods to |
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* <tt>get</tt>, <tt>remove</tt> and <tt>insert</tt> an element at the |
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* beginning and end of the list. These operations allow linked lists to be |
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* used as a stack, {@linkplain Queue queue}, or {@linkplain Deque |
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* double-ended queue}. <p> |
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* |
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* The class implements the <tt>Deque</tt> interface, providing |
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* first-in-first-out queue operations for <tt>add</tt>, |
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* <tt>poll</tt>, along with other stack and deque operations.<p> |
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* |
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* All of the operations perform as could be expected for a doubly-linked |
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* list. Operations that index into the list will traverse the list from |
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* the beginning or the end, whichever is closer to the specified index.<p> |
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* |
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* <b>Note that this implementation is not synchronized.</b> If multiple |
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* threads access a list concurrently, and at least one of the threads |
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* modifies the list structurally, it <i>must</i> be synchronized |
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* externally. (A structural modification is any operation that adds or |
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* deletes one or more elements; merely setting the value of an element is not |
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* a structural modification.) This is typically accomplished by |
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* synchronizing on some object that naturally encapsulates the list. If no |
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* such object exists, the list should be "wrapped" using the |
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* Collections.synchronizedList method. This is best done at creation time, |
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* to prevent accidental unsynchronized access to the list: <pre> |
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* List list = Collections.synchronizedList(new LinkedList(...)); |
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* </pre> |
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* |
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* <p>The iterators returned by this class's <tt>iterator</tt> and |
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* <tt>listIterator</tt> methods are <i>fail-fast</i>: if the list is |
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* structurally modified at any time after the iterator is created, in |
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* any way except through the Iterator's own <tt>remove</tt> or |
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* <tt>add</tt> methods, the iterator will throw a {@link |
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* ConcurrentModificationException}. Thus, in the face of concurrent |
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* modification, the iterator fails quickly and cleanly, rather than |
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* risking arbitrary, non-deterministic behavior at an undetermined |
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* time in the future. |
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* |
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* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
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* as it is, generally speaking, impossible to make any hard guarantees in the |
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* presence of unsynchronized concurrent modification. Fail-fast iterators |
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* throw <tt>ConcurrentModificationException</tt> on a best-effort basis. |
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* Therefore, it would be wrong to write a program that depended on this |
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* exception for its correctness: <i>the fail-fast behavior of iterators |
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* should be used only to detect bugs.</i> |
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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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* @author Josh Bloch |
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* @version %I%, %G% |
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* @see List |
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* @see ArrayList |
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* @see Vector |
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* @see Collections#synchronizedList(List) |
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* @since 1.2 |
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* @param <E> the type of elements held in this collection |
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*/ |
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|
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public class LinkedList<E> |
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extends AbstractSequentialList<E> |
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implements List<E>, Deque<E>, Cloneable, java.io.Serializable |
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{ |
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private transient Entry<E> header = new Entry<E>(null, null, null); |
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private transient int size = 0; |
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|
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/** |
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* Constructs an empty list. |
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*/ |
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public LinkedList() { |
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header.next = header.previous = header; |
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} |
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|
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/** |
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* Constructs 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 whose elements are to be placed into this list. |
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* @throws NullPointerException if the specified collection is null. |
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*/ |
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public LinkedList(Collection<? extends E> c) { |
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this(); |
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addAll(c); |
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} |
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|
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/** |
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* Returns the first element in this list. |
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* |
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* @return the first element in this list. |
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* @throws NoSuchElementException if this list is empty. |
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*/ |
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public E getFirst() { |
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if (size==0) |
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throw new NoSuchElementException(); |
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|
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return header.next.element; |
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} |
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|
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/** |
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* Returns the last element in this list. |
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* |
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* @return the last element in this list. |
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* @throws NoSuchElementException if this list is empty. |
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*/ |
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public E getLast() { |
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if (size==0) |
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throw new NoSuchElementException(); |
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|
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return header.previous.element; |
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} |
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|
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/** |
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* Removes and returns the first element from this list. |
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* |
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* @return the first element from this list. |
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* @throws NoSuchElementException if this list is empty. |
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*/ |
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public E removeFirst() { |
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return remove(header.next); |
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} |
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|
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/** |
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* Removes and returns the last element from this list. |
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* |
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* @return the last element from this list. |
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* @throws NoSuchElementException if this list is empty. |
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*/ |
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public E removeLast() { |
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return remove(header.previous); |
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} |
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|
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/** |
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* Inserts the given element at the beginning of this list. |
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* |
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* @param o the element to be inserted at the beginning of this list. |
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*/ |
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public void addFirst(E o) { |
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addBefore(o, header.next); |
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} |
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|
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/** |
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* Appends the given element to the end of this list. (Identical in |
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* function to the <tt>add</tt> method; included only for consistency.) |
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* |
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* @param o the element to be inserted at the end of this list. |
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*/ |
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public void addLast(E o) { |
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addBefore(o, header); |
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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 <tt>(o==null ? e==null |
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* : 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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return indexOf(o) != -1; |
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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 size; |
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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 o element to be appended to this list. |
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* @return <tt>true</tt> (as per the general contract of |
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* <tt>Collection.add</tt>). |
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*/ |
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public boolean add(E o) { |
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addBefore(o, header); |
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return true; |
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} |
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|
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/** |
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* Removes the first occurrence of the specified element in this list. If |
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* the list does not contain the element, it is unchanged. More formally, |
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* removes the element with the lowest index <tt>i</tt> such that |
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* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> (if such an |
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* element exists). |
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* |
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* @param o element to be removed from this list, if present. |
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* @return <tt>true</tt> if the list contained the specified element. |
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*/ |
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public boolean remove(Object o) { |
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if (o==null) { |
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for (Entry<E> e = header.next; e != header; e = e.next) { |
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if (e.element==null) { |
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remove(e); |
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return true; |
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} |
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} |
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} else { |
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for (Entry<E> e = header.next; e != header; e = e.next) { |
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if (o.equals(e.element)) { |
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remove(e); |
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return true; |
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} |
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} |
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} |
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return false; |
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} |
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|
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/** |
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* Appends all of the elements in the specified collection to the end of |
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* this list, in the order that they are returned by the specified |
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* collection's iterator. The behavior of this operation is undefined if |
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* the specified collection is modified while the operation is in |
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* progress. (This implies that the behavior of this call is undefined if |
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* the specified Collection is this list, and this list is nonempty.) |
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* |
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* @param c the elements to be inserted into this list. |
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* @return <tt>true</tt> if this list changed as a result of the call. |
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* @throws NullPointerException if the specified collection is null. |
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*/ |
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public boolean addAll(Collection<? extends E> c) { |
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return addAll(size, c); |
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} |
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|
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/** |
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* Inserts all of the elements in the specified collection into this |
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* list, starting at the specified position. Shifts the element |
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* currently at that position (if any) and any subsequent elements to |
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* the right (increases their indices). The new elements will appear |
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* in the list in the order that they are returned by the |
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* specified collection's iterator. |
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* |
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* @param index index at which to insert first element |
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* from the specified collection. |
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* @param c elements to be inserted into this list. |
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* @return <tt>true</tt> if this list changed as a result of the call. |
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* @throws IndexOutOfBoundsException if the index is out of range |
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* (<tt>index < 0 || index > size()</tt>). |
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* @throws NullPointerException if the specified collection is null. |
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*/ |
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public boolean addAll(int index, Collection<? extends E> c) { |
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if (index < 0 || index > size) |
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throw new IndexOutOfBoundsException("Index: "+index+ |
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", Size: "+size); |
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Object[] a = c.toArray(); |
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int numNew = a.length; |
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if (numNew==0) |
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return false; |
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modCount++; |
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|
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Entry<E> successor = (index==size ? header : entry(index)); |
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Entry<E> predecessor = successor.previous; |
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for (int i=0; i<numNew; i++) { |
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Entry<E> e = new Entry<E>((E)a[i], successor, predecessor); |
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predecessor.next = e; |
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predecessor = e; |
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} |
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successor.previous = predecessor; |
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|
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size += numNew; |
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return true; |
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} |
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|
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/** |
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* Removes all of the elements from this list. |
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*/ |
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public void clear() { |
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Entry<E> e = header.next; |
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while (e != header) { |
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Entry<E> next = e.next; |
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e.next = e.previous = null; |
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e.element = null; |
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e = next; |
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} |
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header.next = header.previous = header; |
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size = 0; |
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modCount++; |
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} |
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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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* |
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* @throws IndexOutOfBoundsException if the index is out of range |
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* (<tt>index < 0 || index > size()</tt>). |
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*/ |
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public E get(int index) { |
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return entry(index).element; |
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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 the |
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* 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 the index is out of range |
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* (<tt>index < 0 || index > size()</tt>). |
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*/ |
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public E set(int index, E element) { |
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Entry<E> e = entry(index); |
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E oldVal = e.element; |
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e.element = element; |
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return oldVal; |
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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 list. |
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* Shifts the element currently at that position (if any) and any |
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* subsequent elements to the right (adds one to their indices). |
336 |
* |
337 |
* @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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* |
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* @throws IndexOutOfBoundsException if the index is out of range |
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* (<tt>index < 0 || index > size()</tt>). |
342 |
*/ |
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public void add(int index, E element) { |
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addBefore(element, (index==size ? header : entry(index))); |
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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. Shifts any |
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* subsequent elements to the left (subtracts one from their indices). |
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* Returns the element that was removed from the list. |
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* |
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* @param index the index of the element to removed. |
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* @return the element previously at the specified position. |
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* |
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* @throws IndexOutOfBoundsException if the index is out of range |
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* (<tt>index < 0 || index > size()</tt>). |
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*/ |
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public E remove(int index) { |
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return remove(entry(index)); |
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} |
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|
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/** |
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* Returns the indexed entry. |
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*/ |
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private Entry<E> entry(int index) { |
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if (index < 0 || index >= size) |
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throw new IndexOutOfBoundsException("Index: "+index+ |
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", Size: "+size); |
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Entry<E> e = header; |
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if (index < (size >> 1)) { |
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for (int i = 0; i <= index; i++) |
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e = e.next; |
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} else { |
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for (int i = size; i > index; i--) |
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e = e.previous; |
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} |
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return e; |
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} |
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|
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|
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// Search Operations |
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|
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/** |
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* Returns the index in this list of the first occurrence of the |
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* specified element, or -1 if the List does not contain this |
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* element. More formally, returns the lowest index i such that |
387 |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, or -1 if |
388 |
* there is no such index. |
389 |
* |
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* @param o element to search for. |
391 |
* @return the index in this list of the first occurrence of the |
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* specified element, or -1 if the list does not contain this |
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* element. |
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*/ |
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public int indexOf(Object o) { |
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int index = 0; |
397 |
if (o==null) { |
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for (Entry e = header.next; e != header; e = e.next) { |
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if (e.element==null) |
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return index; |
401 |
index++; |
402 |
} |
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} else { |
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for (Entry e = header.next; e != header; e = e.next) { |
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if (o.equals(e.element)) |
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return index; |
407 |
index++; |
408 |
} |
409 |
} |
410 |
return -1; |
411 |
} |
412 |
|
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/** |
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* Returns the index in this list of the last occurrence of the |
415 |
* specified element, or -1 if the list does not contain this |
416 |
* element. More formally, returns the highest index i such that |
417 |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, or -1 if |
418 |
* there is no such index. |
419 |
* |
420 |
* @param o element to search for. |
421 |
* @return the index in this list of the last occurrence of the |
422 |
* specified element, or -1 if the list does not contain this |
423 |
* element. |
424 |
*/ |
425 |
public int lastIndexOf(Object o) { |
426 |
int index = size; |
427 |
if (o==null) { |
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for (Entry e = header.previous; e != header; e = e.previous) { |
429 |
index--; |
430 |
if (e.element==null) |
431 |
return index; |
432 |
} |
433 |
} else { |
434 |
for (Entry e = header.previous; e != header; e = e.previous) { |
435 |
index--; |
436 |
if (o.equals(e.element)) |
437 |
return index; |
438 |
} |
439 |
} |
440 |
return -1; |
441 |
} |
442 |
|
443 |
// Queue operations. |
444 |
|
445 |
/** |
446 |
* Retrieves, but does not remove, the head (first element) of this list. |
447 |
* @return the head of this list, or <tt>null</tt> if this list is empty. |
448 |
* @since 1.5 |
449 |
*/ |
450 |
public E peek() { |
451 |
if (size==0) |
452 |
return null; |
453 |
return getFirst(); |
454 |
} |
455 |
|
456 |
/** |
457 |
* Retrieves, but does not remove, the head (first element) of this list. |
458 |
* @return the head of this list. |
459 |
* @throws NoSuchElementException if this list is empty. |
460 |
* @since 1.5 |
461 |
*/ |
462 |
public E element() { |
463 |
return getFirst(); |
464 |
} |
465 |
|
466 |
/** |
467 |
* Retrieves and removes the head (first element) of this list. |
468 |
* @return the head of this list, or <tt>null</tt> if this list is empty. |
469 |
* @since 1.5 |
470 |
*/ |
471 |
public E poll() { |
472 |
if (size==0) |
473 |
return null; |
474 |
return removeFirst(); |
475 |
} |
476 |
|
477 |
/** |
478 |
* Retrieves and removes the head (first element) of this list. |
479 |
* @return the head of this list. |
480 |
* @throws NoSuchElementException if this list is empty. |
481 |
* @since 1.5 |
482 |
*/ |
483 |
public E remove() { |
484 |
return removeFirst(); |
485 |
} |
486 |
|
487 |
/** |
488 |
* Adds the specified element as the tail (last element) of this list. |
489 |
* |
490 |
* @param o the element to add. |
491 |
* @return <tt>true</tt> (as per the general contract of |
492 |
* <tt>Queue.offer</tt>) |
493 |
* @since 1.5 |
494 |
*/ |
495 |
public boolean offer(E o) { |
496 |
return add(o); |
497 |
} |
498 |
|
499 |
// Deque operations |
500 |
/** |
501 |
* Inserts the specified element at the front of this list. |
502 |
* |
503 |
* @param e the element to insert |
504 |
* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst}) |
505 |
* @since 1.6 |
506 |
*/ |
507 |
public boolean offerFirst(E e) { |
508 |
addFirst(e); |
509 |
return true; |
510 |
} |
511 |
|
512 |
/** |
513 |
* Inserts the specified element at the end of this list. |
514 |
* |
515 |
* @param e the element to insert |
516 |
* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast}) |
517 |
* @since 1.6 |
518 |
*/ |
519 |
public boolean offerLast(E e) { |
520 |
addLast(e); |
521 |
return true; |
522 |
} |
523 |
|
524 |
/** |
525 |
* Retrieves, but does not remove, the first element of this list, |
526 |
* returning <tt>null</tt> if this list is empty. |
527 |
* |
528 |
* @return the first element of this list, or <tt>null</tt> if |
529 |
* this list is empty |
530 |
* @since 1.6 |
531 |
*/ |
532 |
public E peekFirst() { |
533 |
if (size==0) |
534 |
return null; |
535 |
return getFirst(); |
536 |
} |
537 |
|
538 |
/** |
539 |
* Retrieves, but does not remove, the last element of this list, |
540 |
* returning <tt>null</tt> if this list is empty. |
541 |
* |
542 |
* @return the last element of this list, or <tt>null</tt> if this list |
543 |
* is empty |
544 |
* @since 1.6 |
545 |
*/ |
546 |
public E peekLast() { |
547 |
if (size==0) |
548 |
return null; |
549 |
return getLast(); |
550 |
} |
551 |
|
552 |
/** |
553 |
* Retrieves and removes the first element of this list, or |
554 |
* <tt>null</tt> if this list is empty. |
555 |
* |
556 |
* @return the first element of this list, or <tt>null</tt> if |
557 |
* this list is empty |
558 |
* @since 1.6 |
559 |
*/ |
560 |
public E pollFirst() { |
561 |
if (size==0) |
562 |
return null; |
563 |
return removeFirst(); |
564 |
} |
565 |
|
566 |
/** |
567 |
* Retrieves and removes the last element of this list, or |
568 |
* <tt>null</tt> if this list is empty. |
569 |
* |
570 |
* @return the last element of this list, or <tt>null</tt> if |
571 |
* this list is empty |
572 |
* @since 1.6 |
573 |
*/ |
574 |
public E pollLast() { |
575 |
if (size==0) |
576 |
return null; |
577 |
return removeLast(); |
578 |
} |
579 |
|
580 |
/** |
581 |
* Pushes an element onto the stack represented by this list. In other |
582 |
* words, inserts the element at the front of this list. |
583 |
* |
584 |
* <p>This method is equivalent to {@link #addFirst}. |
585 |
* |
586 |
* @param e the element to push |
587 |
* @since 1.6 |
588 |
*/ |
589 |
public void push(E e) { |
590 |
addFirst(e); |
591 |
} |
592 |
|
593 |
/** |
594 |
* Pops an element from the stack represented by this list. In other |
595 |
* words, removes and returns the first element of this list. |
596 |
* |
597 |
* <p>This method is equivalent to {@link #removeFirst()}. |
598 |
* |
599 |
* @return the element at the front of this list (which is the top |
600 |
* of the stack represented by this list) |
601 |
* @throws NoSuchElementException if this list is empty. |
602 |
* @since 1.6 |
603 |
*/ |
604 |
public E pop() { |
605 |
return removeFirst(); |
606 |
} |
607 |
|
608 |
/** |
609 |
* Removes the first occurrence of the specified element in this |
610 |
* list (when traversing the list from head to tail). If the list |
611 |
* does not contain the element, it is unchanged. |
612 |
* |
613 |
* @param o element to be removed from this list, if present |
614 |
* @return <tt>true</tt> if the list contained the specified element |
615 |
* @since 1.6 |
616 |
*/ |
617 |
public boolean removeFirstOccurrence(Object o) { |
618 |
return remove(o); |
619 |
} |
620 |
|
621 |
/** |
622 |
* Removes the last occurrence of the specified element in this |
623 |
* list (when traversing the list from head to tail). If the list |
624 |
* does not contain the element, it is unchanged. |
625 |
* |
626 |
* @param o element to be removed from this list, if present |
627 |
* @return <tt>true</tt> if the list contained the specified element |
628 |
* @since 1.6 |
629 |
*/ |
630 |
public boolean removeLastOccurrence(Object o) { |
631 |
if (o==null) { |
632 |
for (Entry e = header.previous; e != header; e = e.previous) { |
633 |
if (e.element==null) { |
634 |
remove(e); |
635 |
return true; |
636 |
} |
637 |
} |
638 |
} else { |
639 |
for (Entry e = header.previous; e != header; e = e.previous) { |
640 |
if (o.equals(e.element)) { |
641 |
remove(e); |
642 |
return true; |
643 |
} |
644 |
} |
645 |
} |
646 |
return false; |
647 |
} |
648 |
|
649 |
/** |
650 |
* Returns a list-iterator of the elements in this list (in proper |
651 |
* sequence), starting at the specified position in the list. |
652 |
* Obeys the general contract of <tt>List.listIterator(int)</tt>.<p> |
653 |
* |
654 |
* The list-iterator is <i>fail-fast</i>: if the list is structurally |
655 |
* modified at any time after the Iterator is created, in any way except |
656 |
* through the list-iterator's own <tt>remove</tt> or <tt>add</tt> |
657 |
* methods, the list-iterator will throw a |
658 |
* <tt>ConcurrentModificationException</tt>. Thus, in the face of |
659 |
* concurrent modification, the iterator fails quickly and cleanly, rather |
660 |
* than risking arbitrary, non-deterministic behavior at an undetermined |
661 |
* time in the future. |
662 |
* |
663 |
* @param index index of first element to be returned from the |
664 |
* list-iterator (by a call to <tt>next</tt>). |
665 |
* @return a ListIterator of the elements in this list (in proper |
666 |
* sequence), starting at the specified position in the list. |
667 |
* @throws IndexOutOfBoundsException if the index is out of range |
668 |
* (<tt>index < 0 || index > size()</tt>). |
669 |
* @see List#listIterator(int) |
670 |
*/ |
671 |
public ListIterator<E> listIterator(int index) { |
672 |
return new ListItr(index); |
673 |
} |
674 |
|
675 |
private class ListItr implements ListIterator<E> { |
676 |
private Entry<E> lastReturned = header; |
677 |
private Entry<E> next; |
678 |
private int nextIndex; |
679 |
private int expectedModCount = modCount; |
680 |
|
681 |
ListItr(int index) { |
682 |
if (index < 0 || index > size) |
683 |
throw new IndexOutOfBoundsException("Index: "+index+ |
684 |
", Size: "+size); |
685 |
if (index < (size >> 1)) { |
686 |
next = header.next; |
687 |
for (nextIndex=0; nextIndex<index; nextIndex++) |
688 |
next = next.next; |
689 |
} else { |
690 |
next = header; |
691 |
for (nextIndex=size; nextIndex>index; nextIndex--) |
692 |
next = next.previous; |
693 |
} |
694 |
} |
695 |
|
696 |
public boolean hasNext() { |
697 |
return nextIndex != size; |
698 |
} |
699 |
|
700 |
public E next() { |
701 |
checkForComodification(); |
702 |
if (nextIndex == size) |
703 |
throw new NoSuchElementException(); |
704 |
|
705 |
lastReturned = next; |
706 |
next = next.next; |
707 |
nextIndex++; |
708 |
return lastReturned.element; |
709 |
} |
710 |
|
711 |
public boolean hasPrevious() { |
712 |
return nextIndex != 0; |
713 |
} |
714 |
|
715 |
public E previous() { |
716 |
if (nextIndex == 0) |
717 |
throw new NoSuchElementException(); |
718 |
|
719 |
lastReturned = next = next.previous; |
720 |
nextIndex--; |
721 |
checkForComodification(); |
722 |
return lastReturned.element; |
723 |
} |
724 |
|
725 |
public int nextIndex() { |
726 |
return nextIndex; |
727 |
} |
728 |
|
729 |
public int previousIndex() { |
730 |
return nextIndex-1; |
731 |
} |
732 |
|
733 |
public void remove() { |
734 |
checkForComodification(); |
735 |
Entry<E> lastNext = lastReturned.next; |
736 |
try { |
737 |
LinkedList.this.remove(lastReturned); |
738 |
} catch (NoSuchElementException e) { |
739 |
throw new IllegalStateException(); |
740 |
} |
741 |
if (next==lastReturned) |
742 |
next = lastNext; |
743 |
else |
744 |
nextIndex--; |
745 |
lastReturned = header; |
746 |
expectedModCount++; |
747 |
} |
748 |
|
749 |
public void set(E o) { |
750 |
if (lastReturned == header) |
751 |
throw new IllegalStateException(); |
752 |
checkForComodification(); |
753 |
lastReturned.element = o; |
754 |
} |
755 |
|
756 |
public void add(E o) { |
757 |
checkForComodification(); |
758 |
lastReturned = header; |
759 |
addBefore(o, next); |
760 |
nextIndex++; |
761 |
expectedModCount++; |
762 |
} |
763 |
|
764 |
final void checkForComodification() { |
765 |
if (modCount != expectedModCount) |
766 |
throw new ConcurrentModificationException(); |
767 |
} |
768 |
} |
769 |
|
770 |
private static class Entry<E> { |
771 |
E element; |
772 |
Entry<E> next; |
773 |
Entry<E> previous; |
774 |
|
775 |
Entry(E element, Entry<E> next, Entry<E> previous) { |
776 |
this.element = element; |
777 |
this.next = next; |
778 |
this.previous = previous; |
779 |
} |
780 |
} |
781 |
|
782 |
private Entry<E> addBefore(E o, Entry<E> e) { |
783 |
Entry<E> newEntry = new Entry<E>(o, e, e.previous); |
784 |
newEntry.previous.next = newEntry; |
785 |
newEntry.next.previous = newEntry; |
786 |
size++; |
787 |
modCount++; |
788 |
return newEntry; |
789 |
} |
790 |
|
791 |
private E remove(Entry<E> e) { |
792 |
if (e == header) |
793 |
throw new NoSuchElementException(); |
794 |
|
795 |
E result = e.element; |
796 |
e.previous.next = e.next; |
797 |
e.next.previous = e.previous; |
798 |
e.next = e.previous = null; |
799 |
e.element = null; |
800 |
size--; |
801 |
modCount++; |
802 |
return result; |
803 |
} |
804 |
|
805 |
/** |
806 |
* Returns a shallow copy of this <tt>LinkedList</tt>. (The elements |
807 |
* themselves are not cloned.) |
808 |
* |
809 |
* @return a shallow copy of this <tt>LinkedList</tt> instance. |
810 |
*/ |
811 |
public Object clone() { |
812 |
LinkedList<E> clone = null; |
813 |
try { |
814 |
clone = (LinkedList<E>) super.clone(); |
815 |
} catch (CloneNotSupportedException e) { |
816 |
throw new InternalError(); |
817 |
} |
818 |
|
819 |
// Put clone into "virgin" state |
820 |
clone.header = new Entry<E>(null, null, null); |
821 |
clone.header.next = clone.header.previous = clone.header; |
822 |
clone.size = 0; |
823 |
clone.modCount = 0; |
824 |
|
825 |
// Initialize clone with our elements |
826 |
for (Entry<E> e = header.next; e != header; e = e.next) |
827 |
clone.add(e.element); |
828 |
|
829 |
return clone; |
830 |
} |
831 |
|
832 |
/** |
833 |
* Returns an array containing all of the elements in this list |
834 |
* in the correct order. |
835 |
* |
836 |
* @return an array containing all of the elements in this list |
837 |
* in the correct order. |
838 |
*/ |
839 |
public Object[] toArray() { |
840 |
Object[] result = new Object[size]; |
841 |
int i = 0; |
842 |
for (Entry<E> e = header.next; e != header; e = e.next) |
843 |
result[i++] = e.element; |
844 |
return result; |
845 |
} |
846 |
|
847 |
/** |
848 |
* Returns an array containing all of the elements in this list in |
849 |
* the correct order; the runtime type of the returned array is that of |
850 |
* the specified array. If the list fits in the specified array, it |
851 |
* is returned therein. Otherwise, a new array is allocated with the |
852 |
* runtime type of the specified array and the size of this list.<p> |
853 |
* |
854 |
* If the list fits in the specified array with room to spare |
855 |
* (i.e., the array has more elements than the list), |
856 |
* the element in the array immediately following the end of the |
857 |
* collection is set to null. This is useful in determining the length |
858 |
* of the list <i>only</i> if the caller knows that the list |
859 |
* does not contain any null elements. |
860 |
* |
861 |
* @param a the array into which the elements of the list are to |
862 |
* be stored, if it is big enough; otherwise, a new array of the |
863 |
* same runtime type is allocated for this purpose. |
864 |
* @return an array containing the elements of the list. |
865 |
* @throws ArrayStoreException if the runtime type of a is not a |
866 |
* supertype of the runtime type of every element in this list. |
867 |
* @throws NullPointerException if the specified array is null. |
868 |
*/ |
869 |
public <T> T[] toArray(T[] a) { |
870 |
if (a.length < size) |
871 |
a = (T[])java.lang.reflect.Array.newInstance( |
872 |
a.getClass().getComponentType(), size); |
873 |
int i = 0; |
874 |
Object[] result = a; |
875 |
for (Entry<E> e = header.next; e != header; e = e.next) |
876 |
result[i++] = e.element; |
877 |
|
878 |
if (a.length > size) |
879 |
a[size] = null; |
880 |
|
881 |
return a; |
882 |
} |
883 |
|
884 |
private static final long serialVersionUID = 876323262645176354L; |
885 |
|
886 |
/** |
887 |
* Save the state of this <tt>LinkedList</tt> instance to a stream (that |
888 |
* is, serialize it). |
889 |
* |
890 |
* @serialData The size of the list (the number of elements it |
891 |
* contains) is emitted (int), followed by all of its |
892 |
* elements (each an Object) in the proper order. |
893 |
*/ |
894 |
private void writeObject(java.io.ObjectOutputStream s) |
895 |
throws java.io.IOException { |
896 |
// Write out any hidden serialization magic |
897 |
s.defaultWriteObject(); |
898 |
|
899 |
// Write out size |
900 |
s.writeInt(size); |
901 |
|
902 |
// Write out all elements in the proper order. |
903 |
for (Entry e = header.next; e != header; e = e.next) |
904 |
s.writeObject(e.element); |
905 |
} |
906 |
|
907 |
/** |
908 |
* Reconstitute this <tt>LinkedList</tt> instance from a stream (that is |
909 |
* deserialize it). |
910 |
*/ |
911 |
private void readObject(java.io.ObjectInputStream s) |
912 |
throws java.io.IOException, ClassNotFoundException { |
913 |
// Read in any hidden serialization magic |
914 |
s.defaultReadObject(); |
915 |
|
916 |
// Read in size |
917 |
int size = s.readInt(); |
918 |
|
919 |
// Initialize header |
920 |
header = new Entry<E>(null, null, null); |
921 |
header.next = header.previous = header; |
922 |
|
923 |
// Read in all elements in the proper order. |
924 |
for (int i=0; i<size; i++) |
925 |
addBefore((E)s.readObject(), header); |
926 |
} |
927 |
} |