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/* |
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* %W% %E% |
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* |
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* Copyright 2004 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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|
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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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/** |
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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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* @param e 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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public boolean add(E e) { |
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addBefore(e, header); |
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return true; |
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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 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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* |
355 |
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* @throws IndexOutOfBoundsException if the specified index is out of |
356 |
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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. |
458 |
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* @return the head of this queue. |
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* @throws NoSuchElementException if this queue is empty. |
458 |
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* @return the head of this list. |
459 |
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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. |
479 |
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* @return the head of this queue. |
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* @throws NoSuchElementException if this queue is empty. |
479 |
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* @return the head of this list. |
480 |
> |
* @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() { |
487 |
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/** |
488 |
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* Adds the specified element as the tail (last element) of this list. |
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* |
490 |
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* @param o the element to add. |
490 |
> |
* @param e the element to add. |
491 |
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* @return <tt>true</tt> (as per the general contract of |
492 |
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* <tt>Queue.offer</tt>) |
493 |
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* @since 1.5 |
494 |
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*/ |
495 |
< |
public boolean offer(E o) { |
496 |
< |
return add(o); |
495 |
> |
public boolean offer(E e) { |
496 |
> |
return add(e); |
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 |
|
/** |
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 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 |
|
* @see List#listIterator(int) |
670 |
|
*/ |
671 |
|
public ListIterator<E> listIterator(int index) { |
746 |
|
expectedModCount++; |
747 |
|
} |
748 |
|
|
749 |
< |
public void set(E o) { |
749 |
> |
public void set(E e) { |
750 |
|
if (lastReturned == header) |
751 |
|
throw new IllegalStateException(); |
752 |
|
checkForComodification(); |
753 |
< |
lastReturned.element = o; |
753 |
> |
lastReturned.element = e; |
754 |
|
} |
755 |
|
|
756 |
< |
public void add(E o) { |
756 |
> |
public void add(E e) { |
757 |
|
checkForComodification(); |
758 |
|
lastReturned = header; |
759 |
< |
addBefore(o, next); |
759 |
> |
addBefore(e, next); |
760 |
|
nextIndex++; |
761 |
|
expectedModCount++; |
762 |
|
} |
779 |
|
} |
780 |
|
} |
781 |
|
|
782 |
< |
private Entry<E> addBefore(E o, Entry<E> e) { |
783 |
< |
Entry<E> newEntry = new Entry<E>(o, e, e.previous); |
782 |
> |
private Entry<E> addBefore(E e, Entry<E> entry) { |
783 |
> |
Entry<E> newEntry = new Entry<E>(e, entry, entry.previous); |
784 |
|
newEntry.previous.next = newEntry; |
785 |
|
newEntry.next.previous = newEntry; |
786 |
|
size++; |