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/* |
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* @(#)LinkedList.java 1.43 01/12/03 |
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* %W% %E% |
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* |
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* Copyright 2002 Sun Microsystems, Inc. All rights reserved. |
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* Copyright 2003 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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package java.util; |
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/** |
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– |
* <b>JSR166: Added Queue operations</b>.<p> |
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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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* 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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* |
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* All of the stack/queue/deque operations could be easily recast in terms of |
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* the standard list operations. They're included here primarily for |
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* convenience, though they may run slightly faster than the equivalent List |
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* operations.<p> |
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* The class implements the <tt>Queue</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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* |
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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 begining or the end, whichever is closer to the specified index.<p> |
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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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* <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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* 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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* should be used only to detect bugs.</i><p> |
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* |
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* 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 1.43, 12/03/01 |
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* @see java.util.List |
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* @see java.util.ArrayList |
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* @see java.util.Vector |
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* @see java.util.Collections#synchronizedList(java.util.List) |
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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 extends AbstractSequentialList |
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implements List, Queue, Cloneable, java.io.Serializable |
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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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{ |
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private transient Entry header = new Entry(null, null, null); |
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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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* @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 c) { |
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this(); |
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addAll(c); |
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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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* @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 Object getFirst() { |
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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 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 Object getLast() { |
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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 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 Object removeFirst() { |
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Object first = header.next.element; |
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public E removeFirst() { |
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E first = header.next.element; |
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remove(header.next); |
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return first; |
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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 Object removeLast() { |
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Object last = header.previous.element; |
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public E removeLast() { |
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E last = header.previous.element; |
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remove(header.previous); |
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return last; |
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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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* |
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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(Object o) { |
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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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> |
* |
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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(Object o) { |
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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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* @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(Object o) { |
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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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public boolean remove(Object o) { |
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if (o==null) { |
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< |
for (Entry e = header.next; e != header; e = e.next) { |
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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 { |
223 |
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for (Entry e = header.next; e != header; e = e.next) { |
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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; |
242 |
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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. |
244 |
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*/ |
245 |
< |
public boolean addAll(Collection c) { |
245 |
> |
public boolean addAll(Collection<? extends E> c) { |
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return addAll(size, c); |
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} |
248 |
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|
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* range (<tt>index < 0 || index > size()</tt>). |
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* @throws NullPointerException if the specified collection is null. |
264 |
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*/ |
265 |
< |
public boolean addAll(int index, Collection c) { |
266 |
< |
int numNew = c.size(); |
265 |
> |
public boolean addAll(int index, Collection<? extends E> c) { |
266 |
> |
if (index < 0 || index > size) |
267 |
> |
throw new IndexOutOfBoundsException("Index: "+index+ |
268 |
> |
", Size: "+size); |
269 |
> |
Object[] a = c.toArray(); |
270 |
> |
int numNew = a.length; |
271 |
|
if (numNew==0) |
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return false; |
273 |
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modCount++; |
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|
275 |
< |
Entry successor = (index==size ? header : entry(index)); |
276 |
< |
Entry predecessor = successor.previous; |
266 |
< |
Iterator it = c.iterator(); |
275 |
> |
Entry<E> successor = (index==size ? header : entry(index)); |
276 |
> |
Entry<E> predecessor = successor.previous; |
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for (int i=0; i<numNew; i++) { |
278 |
< |
Entry e = new Entry(it.next(), successor, predecessor); |
278 |
> |
Entry<E> e = new Entry<E>((E)a[i], successor, predecessor); |
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predecessor.next = e; |
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predecessor = e; |
281 |
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} |
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* |
303 |
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* @param index index of element to return. |
304 |
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* @return the element at the specified position in this list. |
305 |
< |
* |
305 |
> |
* |
306 |
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* @throws IndexOutOfBoundsException if the specified index is is out of |
307 |
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* range (<tt>index < 0 || index >= size()</tt>). |
308 |
|
*/ |
309 |
< |
public Object get(int index) { |
309 |
> |
public E get(int index) { |
310 |
|
return entry(index).element; |
311 |
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} |
312 |
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|
320 |
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* @throws IndexOutOfBoundsException if the specified index is out of |
321 |
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* range (<tt>index < 0 || index >= size()</tt>). |
322 |
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*/ |
323 |
< |
public Object set(int index, Object element) { |
324 |
< |
Entry e = entry(index); |
325 |
< |
Object oldVal = e.element; |
323 |
> |
public E set(int index, E element) { |
324 |
> |
Entry<E> e = entry(index); |
325 |
> |
E oldVal = e.element; |
326 |
|
e.element = element; |
327 |
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return oldVal; |
328 |
|
} |
334 |
|
* |
335 |
|
* @param index index at which the specified element is to be inserted. |
336 |
|
* @param element element to be inserted. |
337 |
< |
* |
337 |
> |
* |
338 |
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* @throws IndexOutOfBoundsException if the specified index is out of |
339 |
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* range (<tt>index < 0 || index > size()</tt>). |
340 |
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*/ |
341 |
< |
public void add(int index, Object element) { |
341 |
> |
public void add(int index, E element) { |
342 |
|
addBefore(element, (index==size ? header : entry(index))); |
343 |
|
} |
344 |
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|
349 |
|
* |
350 |
|
* @param index the index of the element to removed. |
351 |
|
* @return the element previously at the specified position. |
352 |
< |
* |
352 |
> |
* |
353 |
|
* @throws IndexOutOfBoundsException if the specified index is out of |
354 |
|
* range (<tt>index < 0 || index >= size()</tt>). |
355 |
|
*/ |
356 |
< |
public Object remove(int index) { |
357 |
< |
Entry e = entry(index); |
356 |
> |
public E remove(int index) { |
357 |
> |
Entry<E> e = entry(index); |
358 |
|
remove(e); |
359 |
|
return e.element; |
360 |
|
} |
362 |
|
/** |
363 |
|
* Return the indexed entry. |
364 |
|
*/ |
365 |
< |
private Entry entry(int index) { |
365 |
> |
private Entry<E> entry(int index) { |
366 |
|
if (index < 0 || index >= size) |
367 |
|
throw new IndexOutOfBoundsException("Index: "+index+ |
368 |
|
", Size: "+size); |
369 |
< |
Entry e = header; |
369 |
> |
Entry<E> e = header; |
370 |
|
if (index < (size >> 1)) { |
371 |
|
for (int i = 0; i <= index; i++) |
372 |
|
e = e.next; |
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 queue, or <tt>null</tt> if this queue 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 queue. |
459 |
+ |
* @throws NoSuchElementException if this queue 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 queue, or <tt>null</tt> if this queue 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 queue. |
480 |
+ |
* @throws NoSuchElementException if this queue 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 |
|
/** |
500 |
|
* Returns a list-iterator of the elements in this list (in proper |
501 |
|
* sequence), starting at the specified position in the list. |
516 |
|
* sequence), starting at the specified position in the list. |
517 |
|
* @throws IndexOutOfBoundsException if index is out of range |
518 |
|
* (<tt>index < 0 || index > size()</tt>). |
519 |
< |
* @see java.util.List#listIterator(int) |
519 |
> |
* @see List#listIterator(int) |
520 |
|
*/ |
521 |
< |
public ListIterator listIterator(int index) { |
521 |
> |
public ListIterator<E> listIterator(int index) { |
522 |
|
return new ListItr(index); |
523 |
|
} |
524 |
|
|
525 |
< |
private class ListItr implements ListIterator { |
526 |
< |
private Entry lastReturned = header; |
527 |
< |
private Entry next; |
525 |
> |
private class ListItr implements ListIterator<E> { |
526 |
> |
private Entry<E> lastReturned = header; |
527 |
> |
private Entry<E> next; |
528 |
|
private int nextIndex; |
529 |
|
private int expectedModCount = modCount; |
530 |
|
|
547 |
|
return nextIndex != size; |
548 |
|
} |
549 |
|
|
550 |
< |
public Object next() { |
550 |
> |
public E next() { |
551 |
|
checkForComodification(); |
552 |
|
if (nextIndex == size) |
553 |
|
throw new NoSuchElementException(); |
562 |
|
return nextIndex != 0; |
563 |
|
} |
564 |
|
|
565 |
< |
public Object previous() { |
565 |
> |
public E previous() { |
566 |
|
if (nextIndex == 0) |
567 |
|
throw new NoSuchElementException(); |
568 |
|
|
595 |
|
expectedModCount++; |
596 |
|
} |
597 |
|
|
598 |
< |
public void set(Object o) { |
598 |
> |
public void set(E o) { |
599 |
|
if (lastReturned == header) |
600 |
|
throw new IllegalStateException(); |
601 |
|
checkForComodification(); |
602 |
|
lastReturned.element = o; |
603 |
|
} |
604 |
|
|
605 |
< |
public void add(Object o) { |
605 |
> |
public void add(E o) { |
606 |
|
checkForComodification(); |
607 |
|
lastReturned = header; |
608 |
|
addBefore(o, next); |
616 |
|
} |
617 |
|
} |
618 |
|
|
619 |
< |
private static class Entry { |
620 |
< |
Object element; |
621 |
< |
Entry next; |
622 |
< |
Entry previous; |
619 |
> |
private static class Entry<E> { |
620 |
> |
E element; |
621 |
> |
Entry<E> next; |
622 |
> |
Entry<E> previous; |
623 |
|
|
624 |
< |
Entry(Object element, Entry next, Entry previous) { |
624 |
> |
Entry(E element, Entry<E> next, Entry<E> previous) { |
625 |
|
this.element = element; |
626 |
|
this.next = next; |
627 |
|
this.previous = previous; |
628 |
|
} |
629 |
|
} |
630 |
|
|
631 |
< |
private Entry addBefore(Object o, Entry e) { |
632 |
< |
Entry newEntry = new Entry(o, e, e.previous); |
631 |
> |
private Entry<E> addBefore(E o, Entry<E> e) { |
632 |
> |
Entry<E> newEntry = new Entry<E>(o, e, e.previous); |
633 |
|
newEntry.previous.next = newEntry; |
634 |
|
newEntry.next.previous = newEntry; |
635 |
|
size++; |
637 |
|
return newEntry; |
638 |
|
} |
639 |
|
|
640 |
< |
private void remove(Entry e) { |
640 |
> |
private void remove(Entry<E> e) { |
641 |
|
if (e == header) |
642 |
|
throw new NoSuchElementException(); |
643 |
|
|
654 |
|
* @return a shallow copy of this <tt>LinkedList</tt> instance. |
655 |
|
*/ |
656 |
|
public Object clone() { |
657 |
< |
LinkedList clone = null; |
658 |
< |
try { |
659 |
< |
clone = (LinkedList)super.clone(); |
660 |
< |
} catch (CloneNotSupportedException e) { |
657 |
> |
LinkedList<E> clone = null; |
658 |
> |
try { |
659 |
> |
clone = (LinkedList<E>) super.clone(); |
660 |
> |
} catch (CloneNotSupportedException e) { |
661 |
|
throw new InternalError(); |
662 |
|
} |
663 |
|
|
664 |
|
// Put clone into "virgin" state |
665 |
< |
clone.header = new Entry(null, null, null); |
665 |
> |
clone.header = new Entry<E>(null, null, null); |
666 |
|
clone.header.next = clone.header.previous = clone.header; |
667 |
|
clone.size = 0; |
668 |
|
clone.modCount = 0; |
669 |
|
|
670 |
|
// Initialize clone with our elements |
671 |
< |
for (Entry e = header.next; e != header; e = e.next) |
671 |
> |
for (Entry<E> e = header.next; e != header; e = e.next) |
672 |
|
clone.add(e.element); |
673 |
|
|
674 |
|
return clone; |
684 |
|
public Object[] toArray() { |
685 |
|
Object[] result = new Object[size]; |
686 |
|
int i = 0; |
687 |
< |
for (Entry e = header.next; e != header; e = e.next) |
687 |
> |
for (Entry<E> e = header.next; e != header; e = e.next) |
688 |
|
result[i++] = e.element; |
689 |
|
return result; |
690 |
|
} |
711 |
|
* supertype of the runtime type of every element in this list. |
712 |
|
* @throws NullPointerException if the specified array is null. |
713 |
|
*/ |
714 |
< |
public Object[] toArray(Object a[]) { |
714 |
> |
public <T> T[] toArray(T[] a) { |
715 |
|
if (a.length < size) |
716 |
< |
a = (Object[])java.lang.reflect.Array.newInstance( |
716 |
> |
a = (T[])java.lang.reflect.Array.newInstance( |
717 |
|
a.getClass().getComponentType(), size); |
718 |
|
int i = 0; |
719 |
< |
for (Entry e = header.next; e != header; e = e.next) |
720 |
< |
a[i++] = e.element; |
719 |
> |
Object[] result = a; |
720 |
> |
for (Entry<E> e = header.next; e != header; e = e.next) |
721 |
> |
result[i++] = e.element; |
722 |
|
|
723 |
|
if (a.length > size) |
724 |
|
a[size] = null; |
734 |
|
* |
735 |
|
* @serialData The size of the list (the number of elements it |
736 |
|
* contains) is emitted (int), followed by all of its |
737 |
< |
* elements (each an Object) in the proper order. |
737 |
> |
* elements (each an Object) in the proper order. |
738 |
|
*/ |
739 |
< |
private synchronized void writeObject(java.io.ObjectOutputStream s) |
739 |
> |
private void writeObject(java.io.ObjectOutputStream s) |
740 |
|
throws java.io.IOException { |
741 |
|
// Write out any hidden serialization magic |
742 |
|
s.defaultWriteObject(); |
753 |
|
* Reconstitute this <tt>LinkedList</tt> instance from a stream (that is |
754 |
|
* deserialize it). |
755 |
|
*/ |
756 |
< |
private synchronized void readObject(java.io.ObjectInputStream s) |
756 |
> |
private void readObject(java.io.ObjectInputStream s) |
757 |
|
throws java.io.IOException, ClassNotFoundException { |
758 |
|
// Read in any hidden serialization magic |
759 |
|
s.defaultReadObject(); |
762 |
|
int size = s.readInt(); |
763 |
|
|
764 |
|
// Initialize header |
765 |
< |
header = new Entry(null, null, null); |
765 |
> |
header = new Entry<E>(null, null, null); |
766 |
|
header.next = header.previous = header; |
767 |
|
|
768 |
|
// Read in all elements in the proper order. |
769 |
|
for (int i=0; i<size; i++) |
770 |
< |
add(s.readObject()); |
770 |
> |
addBefore((E)s.readObject(), header); |
771 |
|
} |
705 |
– |
|
706 |
– |
public Object peek() { |
707 |
– |
if (size==0) |
708 |
– |
return null; |
709 |
– |
return header.previous.element; |
710 |
– |
} |
711 |
– |
|
712 |
– |
public Object element() { |
713 |
– |
if (size==0) |
714 |
– |
throw new NoSuchElementException(); |
715 |
– |
return header.previous.element; |
716 |
– |
} |
717 |
– |
|
718 |
– |
public Object poll() { |
719 |
– |
if (size==0) |
720 |
– |
return null; |
721 |
– |
Object last = header.previous.element; |
722 |
– |
remove(header.previous); |
723 |
– |
return last; |
724 |
– |
} |
725 |
– |
|
726 |
– |
public Object remove() { |
727 |
– |
if (size==0) |
728 |
– |
throw new NoSuchElementException(); |
729 |
– |
Object last = header.previous.element; |
730 |
– |
remove(header.previous); |
731 |
– |
return last; |
732 |
– |
} |
733 |
– |
|
734 |
– |
public boolean offer(Object x) { |
735 |
– |
return add(x); |
736 |
– |
} |
737 |
– |
|
772 |
|
} |