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* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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*/ |
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package java.util; |
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package java.util; |
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/** |
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* Linked list implementation of the <tt>List</tt> interface. Implements all |
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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, queue, or double-ended queue ({@link Deque}).<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. |
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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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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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return add(o); |
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} |
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// Deque operations |
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/** |
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* Inserts the specified element to the front this deque. |
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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 to the end this deque. |
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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 deque, |
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* returning <tt>null</tt> if this deque is empty. |
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* |
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* @return the first element of this deque, or <tt>null</tt> if |
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* this deque 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 removeFirst(); |
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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 deque, |
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* returning <tt>null</tt> if this deque is empty. |
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* |
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* @return the last element of this deque, or <tt>null</tt> if this deque |
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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 removeLast(); |
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} |
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|
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/** |
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* Retrieves and removes the first element of this deque, or |
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* <tt>null</tt> if this deque is empty. |
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* |
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* @return the first element of this deque, or <tt>null</tt> if |
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* this deque is empty |
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* @since 1.6 |
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*/ |
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public E pollFirst() { |
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if (size==0) |
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return null; |
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return removeFirst(); |
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} |
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|
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/** |
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* Retrieves and removes the last element of this deque, or |
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* <tt>null</tt> if this deque is empty. |
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* |
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* @return the last element of this deque, or <tt>null</tt> if |
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* this deque is empty |
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* @since 1.6 |
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*/ |
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public E pollLast() { |
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if (size==0) |
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return null; |
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return removeLast(); |
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} |
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|
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/** |
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* Pushes an element onto the stack represented by this deque. In other |
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* words, inserts the element to the front this deque. |
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* |
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* <p>This method is equivalent to {@link #addFirst}. |
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* |
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* @param e the element to push |
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* @since 1.6 |
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*/ |
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public void push(E e) { |
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addFirst(e); |
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} |
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|
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/** |
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* Pops an element from the stack represented by this deque. In other |
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* words, removes and returns the the first element of this deque. |
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* |
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* <p>This method is equivalent to {@link #removeFirst()}. |
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* |
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* @return the element at the front of this deque (which is the top |
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* of the stack represented by this deque) |
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* @throws NoSuchElementException if this deque is empty |
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* @since 1.6 |
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*/ |
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public E pop() { |
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return removeFirst(); |
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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 |
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* deque (when traversing the deque from head to tail). If the deque |
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* does not contain the element, it is unchanged. |
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* |
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* @param e element to be removed from this deque, if present |
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* @return <tt>true</tt> if the deque contained the specified element |
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* @since 1.6 |
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*/ |
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public boolean removeFirstOccurrence(Object e) { |
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return remove(e); |
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} |
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|
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/** |
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* Removes the last occurrence of the specified element in this |
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* deque (when traversing the deque from head to tail). If the deque |
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* does not contain the element, it is unchanged. |
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* |
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* @param o element to be removed from this deque, if present |
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* @return <tt>true</tt> if the deque contained the specified element |
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* @since 1.6 |
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*/ |
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public boolean removeLastOccurrence(Object o) { |
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if (o==null) { |
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for (Entry e = header.previous; e != header; e = e.previous) { |
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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 = header.previous; e != header; e = e.previous) { |
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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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* Returns a list-iterator of the elements in this list (in proper |
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* sequence), starting at the specified position in the list. |