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/* |
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* %W% %E% |
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* |
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* Copyright 2003 Sun Microsystems, Inc. All rights reserved. |
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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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* 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, queue, or double-ended queue (deque).<p> |
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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>Queue</tt> interface, providing |
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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>, etc. Other stack and deque operations could be |
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* easily recast in terms of the standard list operations. They're |
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* included here primarily for convenience, though they may run |
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* slightly faster than the equivalent List operations.<p> |
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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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* 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><p> |
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* </pre> |
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* |
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* The iterators returned by the this class's <tt>iterator</tt> and |
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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 any way |
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* except through the Iterator's own <tt>remove</tt> or <tt>add</tt> methods, |
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* the iterator will throw a <tt>ConcurrentModificationException</tt>. Thus, |
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* in the face of concurrent modification, the iterator fails quickly and |
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* cleanly, rather than risking arbitrary, non-deterministic behavior at an |
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* undetermined time in the future. |
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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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* 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><p> |
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* should be used only to detect bugs.</i> |
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* |
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* This class is a member of the |
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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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public class LinkedList<E> |
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extends AbstractSequentialList<E> |
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implements List<E>, Queue<E>, Cloneable, java.io.Serializable |
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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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* 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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* @param e 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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public void addFirst(E e) { |
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addBefore(e, 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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* @param e 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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public void addLast(E e) { |
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addBefore(e, header); |
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} |
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|
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/** |
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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 specified index is out of |
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* range (<tt>index < 0 || index > size()</tt>). |
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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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* @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 specified index is is out of |
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* range (<tt>index < 0 || index >= size()</tt>). |
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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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* @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 specified index is out of |
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* range (<tt>index < 0 || index >= size()</tt>). |
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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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* @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 specified index is out of |
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* range (<tt>index < 0 || index > size()</tt>). |
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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 void add(int index, E element) { |
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addBefore(element, (index==size ? header : entry(index))); |
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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 specified index is out of |
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* range (<tt>index < 0 || index >= size()</tt>). |
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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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* Return the indexed entry. |
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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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|
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/** |
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* Retrieves, but does not remove, the head (first element) of this list. |
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* @return the head of this queue, or <tt>null</tt> if this queue is empty. |
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* @return the head of this list, or <tt>null</tt> if this list is empty. |
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* @since 1.5 |
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*/ |
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public E peek() { |
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|
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/** |
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* Retrieves, but does not remove, the head (first element) of this list. |
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* @return the head of this queue. |
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* @throws NoSuchElementException if this queue is empty. |
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* @return the head of this list. |
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* @throws NoSuchElementException if this list is empty. |
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* @since 1.5 |
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*/ |
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public E element() { |
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|
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/** |
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* Retrieves and removes the head (first element) of this list. |
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* @return the head of this queue, or <tt>null</tt> if this queue is empty. |
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* @return the head of this list, or <tt>null</tt> if this list is empty. |
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* @since 1.5 |
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*/ |
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public E poll() { |
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|
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/** |
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* Retrieves and removes the head (first element) of this list. |
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* @return the head of this queue. |
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* @throws NoSuchElementException if this queue is empty. |
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* @return the head of this list. |
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* @throws NoSuchElementException if this list is empty. |
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* @since 1.5 |
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*/ |
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public E remove() { |
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return add(o); |
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} |
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|
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// Deque operations |
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/** |
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* Inserts the specified element at the front of this list. |
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* |
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* @param e the element to insert |
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* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst}) |
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* @since 1.6 |
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*/ |
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public boolean offerFirst(E e) { |
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addFirst(e); |
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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 end of this list. |
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* |
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* @param e the element to insert |
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* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast}) |
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* @since 1.6 |
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*/ |
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public boolean offerLast(E e) { |
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addLast(e); |
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return true; |
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} |
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|
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/** |
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* Retrieves, but does not remove, the first element of this list, |
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* returning <tt>null</tt> if this list is empty. |
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* |
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* @return the first element of this list, or <tt>null</tt> if |
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* this list is empty |
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* @since 1.6 |
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*/ |
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public E peekFirst() { |
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if (size==0) |
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return null; |
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return getFirst(); |
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} |
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|
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/** |
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* Retrieves, but does not remove, the last element of this list, |
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* returning <tt>null</tt> if this list is empty. |
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* |
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* @return the last element of this list, or <tt>null</tt> if this list |
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* is empty |
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* @since 1.6 |
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*/ |
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public E peekLast() { |
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if (size==0) |
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return null; |
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return getLast(); |
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} |
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|
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/** |
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* Retrieves and removes the first element of this list, or |
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* <tt>null</tt> if this list is empty. |
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* |
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* @return the first element of this list, or <tt>null</tt> if |
557 |
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* this list is empty |
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* @since 1.6 |
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*/ |
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public E pollFirst() { |
561 |
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if (size==0) |
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return null; |
563 |
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return removeFirst(); |
564 |
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} |
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|
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/** |
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* Retrieves and removes the last element of this list, or |
568 |
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* <tt>null</tt> if this list is empty. |
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* |
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* @return the last element of this list, or <tt>null</tt> if |
571 |
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* this list is empty |
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* @since 1.6 |
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*/ |
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public E pollLast() { |
575 |
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if (size==0) |
576 |
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return null; |
577 |
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return removeLast(); |
578 |
+ |
} |
579 |
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|
580 |
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/** |
581 |
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* Pushes an element onto the stack represented by this list. In other |
582 |
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* words, inserts the element at the front of this list. |
583 |
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* |
584 |
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* <p>This method is equivalent to {@link #addFirst}. |
585 |
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* |
586 |
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* @param e the element to push |
587 |
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* @since 1.6 |
588 |
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*/ |
589 |
+ |
public void push(E e) { |
590 |
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addFirst(e); |
591 |
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} |
592 |
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|
593 |
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/** |
594 |
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* Pops an element from the stack represented by this list. In other |
595 |
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* words, removes and returns the first element of this list. |
596 |
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* |
597 |
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* <p>This method is equivalent to {@link #removeFirst()}. |
598 |
+ |
* |
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* @return the element at the front of this list (which is the top |
600 |
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* of the stack represented by this list) |
601 |
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* @throws NoSuchElementException if this list is empty. |
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* @since 1.6 |
603 |
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*/ |
604 |
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public E pop() { |
605 |
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return removeFirst(); |
606 |
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} |
607 |
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|
608 |
+ |
/** |
609 |
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* Removes the first occurrence of the specified element in this |
610 |
+ |
* list (when traversing the list from head to tail). If the list |
611 |
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* does not contain the element, it is unchanged. |
612 |
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* |
613 |
+ |
* @param o element to be removed from this list, if present |
614 |
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* @return <tt>true</tt> if the list contained the specified element |
615 |
+ |
* @since 1.6 |
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*/ |
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public boolean removeFirstOccurrence(Object o) { |
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+ |
return remove(o); |
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} |
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|
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/** |
622 |
+ |
* Removes the last occurrence of the specified element in this |
623 |
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* list (when traversing the list from head to tail). If the list |
624 |
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* 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 |
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} |
646 |
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return false; |
647 |
+ |
} |
648 |
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|
649 |
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/** |
650 |
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* Returns a list-iterator of the elements in this list (in proper |
651 |
|
* sequence), starting at the specified position in the list. |
664 |
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* list-iterator (by a call to <tt>next</tt>). |
665 |
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* @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 index is out of range |
668 |
< |
* (<tt>index < 0 || index > size()</tt>). |
667 |
> |
* @throws IndexOutOfBoundsException if the index is out of range |
668 |
> |
* (<tt>index < 0 || index > size()</tt>). |
669 |
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* @see List#listIterator(int) |
670 |
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*/ |
671 |
|
public ListIterator<E> listIterator(int index) { |