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tim |
1.1 |
/* |
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dl |
1.6 |
* %W% %E% |
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tim |
1.1 |
* |
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jsr166 |
1.15 |
* Copyright 2004 Sun Microsystems, Inc. All rights reserved. |
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tim |
1.1 |
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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*/ |
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dl |
1.17 |
package java.util; |
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1.1 |
|
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/** |
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* Linked list implementation of the <tt>List</tt> interface. Implements all |
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* optional list operations, and permits all elements (including |
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* <tt>null</tt>). In addition to implementing the <tt>List</tt> interface, |
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* the <tt>LinkedList</tt> class provides uniformly named methods to |
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* <tt>get</tt>, <tt>remove</tt> and <tt>insert</tt> an element at the |
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* beginning and end of the list. These operations allow linked lists to be |
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1.19 |
* used as a stack, {@linkplain Queue queue}, or {@linkplain Deque |
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* double-ended queue}. <p> |
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tim |
1.1 |
* |
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1.17 |
* The class implements the <tt>Deque</tt> interface, providing |
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1.3 |
* first-in-first-out queue operations for <tt>add</tt>, |
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1.21 |
* <tt>poll</tt>, along with other stack and deque operations.<p> |
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1.1 |
* |
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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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1.8 |
* the beginning or the end, whichever is closer to the specified index.<p> |
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1.1 |
* |
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* <b>Note that this implementation is not synchronized.</b> If multiple |
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* threads access a list concurrently, and at least one of the threads |
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* modifies the list structurally, it <i>must</i> be synchronized |
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* externally. (A structural modification is any operation that adds or |
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* deletes one or more elements; merely setting the value of an element is not |
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* a structural modification.) This is typically accomplished by |
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* synchronizing on some object that naturally encapsulates the list. If no |
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* such object exists, the list should be "wrapped" using the |
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* Collections.synchronizedList method. This is best done at creation time, |
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* to prevent accidental unsynchronized access to the list: <pre> |
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* List list = Collections.synchronizedList(new LinkedList(...)); |
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* </pre><p> |
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* |
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* The iterators returned by the 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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* |
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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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1.3 |
* throw <tt>ConcurrentModificationException</tt> on a best-effort basis. |
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1.1 |
* 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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1.3 |
* 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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1.1 |
* |
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* @author Josh Bloch |
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1.6 |
* @version %I%, %G% |
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jsr166 |
1.14 |
* @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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1.1 |
* @since 1.2 |
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1.10 |
* @param <E> the type of elements held in this collection |
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1.1 |
*/ |
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1.3 |
public class LinkedList<E> |
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extends AbstractSequentialList<E> |
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1.17 |
implements List<E>, Deque<E>, Cloneable, java.io.Serializable |
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1.1 |
{ |
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1.3 |
private transient Entry<E> header = new Entry<E>(null, null, null); |
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1.1 |
private transient int size = 0; |
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/** |
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* Constructs an empty list. |
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*/ |
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public LinkedList() { |
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header.next = header.previous = header; |
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} |
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/** |
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* Constructs a list containing the elements of the specified |
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* collection, in the order they are returned by the collection's |
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* iterator. |
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* |
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* @param c the collection whose elements are to be placed into this list. |
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* @throws NullPointerException if the specified collection is null. |
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*/ |
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jsr166 |
1.14 |
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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1.1 |
|
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/** |
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* Returns the first element in this list. |
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* |
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* @return the first element in this list. |
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* @throws NoSuchElementException if this list is empty. |
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*/ |
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1.3 |
public E getFirst() { |
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jsr166 |
1.14 |
if (size==0) |
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throw new NoSuchElementException(); |
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tim |
1.1 |
|
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jsr166 |
1.14 |
return header.next.element; |
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tim |
1.1 |
} |
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/** |
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* Returns the last element in this list. |
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* |
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* @return the last element in this list. |
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* @throws NoSuchElementException if this list is empty. |
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*/ |
118 |
dl |
1.3 |
public E getLast() { |
119 |
jsr166 |
1.14 |
if (size==0) |
120 |
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throw new NoSuchElementException(); |
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tim |
1.1 |
|
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jsr166 |
1.14 |
return header.previous.element; |
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tim |
1.1 |
} |
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/** |
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* Removes and returns the first element from this list. |
127 |
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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. |
130 |
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*/ |
131 |
dl |
1.3 |
public E removeFirst() { |
132 |
jsr166 |
1.14 |
return remove(header.next); |
133 |
tim |
1.1 |
} |
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/** |
136 |
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* Removes and returns the last element from this list. |
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* |
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* @return the last element from this list. |
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* @throws NoSuchElementException if this list is empty. |
140 |
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*/ |
141 |
dl |
1.3 |
public E removeLast() { |
142 |
jsr166 |
1.14 |
return remove(header.previous); |
143 |
tim |
1.1 |
} |
144 |
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145 |
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/** |
146 |
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* Inserts the given element at the beginning of this list. |
147 |
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1.3 |
* |
148 |
tim |
1.1 |
* @param o the element to be inserted at the beginning of this list. |
149 |
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*/ |
150 |
dl |
1.3 |
public void addFirst(E o) { |
151 |
jsr166 |
1.14 |
addBefore(o, header.next); |
152 |
tim |
1.1 |
} |
153 |
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154 |
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/** |
155 |
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* Appends the given element to the end of this list. (Identical in |
156 |
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* function to the <tt>add</tt> method; included only for consistency.) |
157 |
dl |
1.3 |
* |
158 |
tim |
1.1 |
* @param o the element to be inserted at the end of this list. |
159 |
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*/ |
160 |
dl |
1.3 |
public void addLast(E o) { |
161 |
jsr166 |
1.14 |
addBefore(o, header); |
162 |
tim |
1.1 |
} |
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164 |
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/** |
165 |
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* Returns <tt>true</tt> if this list contains the specified element. |
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* More formally, returns <tt>true</tt> if and only if this list contains |
167 |
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* at least one element <tt>e</tt> such that <tt>(o==null ? e==null |
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* : o.equals(e))</tt>. |
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* |
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* @param o element whose presence in this list is to be tested. |
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* @return <tt>true</tt> if this list contains the specified element. |
172 |
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*/ |
173 |
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public boolean contains(Object o) { |
174 |
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return indexOf(o) != -1; |
175 |
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} |
176 |
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177 |
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/** |
178 |
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* Returns the number of elements in this list. |
179 |
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* |
180 |
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* @return the number of elements in this list. |
181 |
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*/ |
182 |
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public int size() { |
183 |
jsr166 |
1.14 |
return size; |
184 |
tim |
1.1 |
} |
185 |
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186 |
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/** |
187 |
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* Appends the specified element to the end of this list. |
188 |
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* |
189 |
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* @param o element to be appended to this list. |
190 |
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* @return <tt>true</tt> (as per the general contract of |
191 |
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* <tt>Collection.add</tt>). |
192 |
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*/ |
193 |
dl |
1.3 |
public boolean add(E o) { |
194 |
jsr166 |
1.14 |
addBefore(o, header); |
195 |
tim |
1.1 |
return true; |
196 |
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} |
197 |
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198 |
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/** |
199 |
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* Removes the first occurrence of the specified element in this list. If |
200 |
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* the list does not contain the element, it is unchanged. More formally, |
201 |
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* removes the element with the lowest index <tt>i</tt> such that |
202 |
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* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> (if such an |
203 |
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* element exists). |
204 |
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* |
205 |
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* @param o element to be removed from this list, if present. |
206 |
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* @return <tt>true</tt> if the list contained the specified element. |
207 |
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*/ |
208 |
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public boolean remove(Object o) { |
209 |
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if (o==null) { |
210 |
dl |
1.3 |
for (Entry<E> e = header.next; e != header; e = e.next) { |
211 |
tim |
1.1 |
if (e.element==null) { |
212 |
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remove(e); |
213 |
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return true; |
214 |
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} |
215 |
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} |
216 |
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} else { |
217 |
dl |
1.3 |
for (Entry<E> e = header.next; e != header; e = e.next) { |
218 |
tim |
1.1 |
if (o.equals(e.element)) { |
219 |
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remove(e); |
220 |
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return true; |
221 |
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} |
222 |
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} |
223 |
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} |
224 |
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return false; |
225 |
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} |
226 |
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227 |
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/** |
228 |
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* Appends all of the elements in the specified collection to the end of |
229 |
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* this list, in the order that they are returned by the specified |
230 |
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* collection's iterator. The behavior of this operation is undefined if |
231 |
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* the specified collection is modified while the operation is in |
232 |
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* progress. (This implies that the behavior of this call is undefined if |
233 |
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* the specified Collection is this list, and this list is nonempty.) |
234 |
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* |
235 |
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* @param c the elements to be inserted into this list. |
236 |
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* @return <tt>true</tt> if this list changed as a result of the call. |
237 |
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* @throws NullPointerException if the specified collection is null. |
238 |
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*/ |
239 |
dl |
1.3 |
public boolean addAll(Collection<? extends E> c) { |
240 |
tim |
1.1 |
return addAll(size, c); |
241 |
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} |
242 |
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243 |
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/** |
244 |
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* Inserts all of the elements in the specified collection into this |
245 |
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* list, starting at the specified position. Shifts the element |
246 |
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* currently at that position (if any) and any subsequent elements to |
247 |
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* the right (increases their indices). The new elements will appear |
248 |
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* in the list in the order that they are returned by the |
249 |
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* specified collection's iterator. |
250 |
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* |
251 |
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* @param index index at which to insert first element |
252 |
jsr166 |
1.14 |
* from the specified collection. |
253 |
tim |
1.1 |
* @param c elements to be inserted into this list. |
254 |
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* @return <tt>true</tt> if this list changed as a result of the call. |
255 |
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* @throws IndexOutOfBoundsException if the specified index is out of |
256 |
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* range (<tt>index < 0 || index > size()</tt>). |
257 |
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* @throws NullPointerException if the specified collection is null. |
258 |
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*/ |
259 |
dl |
1.3 |
public boolean addAll(int index, Collection<? extends E> c) { |
260 |
dl |
1.4 |
if (index < 0 || index > size) |
261 |
dl |
1.3 |
throw new IndexOutOfBoundsException("Index: "+index+ |
262 |
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", Size: "+size); |
263 |
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Object[] a = c.toArray(); |
264 |
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int numNew = a.length; |
265 |
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if (numNew==0) |
266 |
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return false; |
267 |
jsr166 |
1.14 |
modCount++; |
268 |
dl |
1.3 |
|
269 |
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Entry<E> successor = (index==size ? header : entry(index)); |
270 |
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Entry<E> predecessor = successor.previous; |
271 |
jsr166 |
1.14 |
for (int i=0; i<numNew; i++) { |
272 |
dl |
1.3 |
Entry<E> e = new Entry<E>((E)a[i], successor, predecessor); |
273 |
tim |
1.1 |
predecessor.next = e; |
274 |
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predecessor = e; |
275 |
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} |
276 |
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successor.previous = predecessor; |
277 |
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278 |
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size += numNew; |
279 |
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return true; |
280 |
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} |
281 |
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282 |
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/** |
283 |
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* Removes all of the elements from this list. |
284 |
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*/ |
285 |
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public void clear() { |
286 |
jsr166 |
1.14 |
Entry<E> e = header.next; |
287 |
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while (e != header) { |
288 |
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Entry<E> next = e.next; |
289 |
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e.next = e.previous = null; |
290 |
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e.element = null; |
291 |
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e = next; |
292 |
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} |
293 |
tim |
1.1 |
header.next = header.previous = header; |
294 |
jozart |
1.12 |
size = 0; |
295 |
jsr166 |
1.14 |
modCount++; |
296 |
tim |
1.1 |
} |
297 |
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|
298 |
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|
299 |
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// Positional Access Operations |
300 |
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|
301 |
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/** |
302 |
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* Returns the element at the specified position in this list. |
303 |
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* |
304 |
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* @param index index of element to return. |
305 |
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* @return the element at the specified position in this list. |
306 |
dl |
1.3 |
* |
307 |
jsr166 |
1.15 |
* @throws IndexOutOfBoundsException if the specified index is out of |
308 |
tim |
1.1 |
* range (<tt>index < 0 || index >= size()</tt>). |
309 |
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*/ |
310 |
dl |
1.3 |
public E get(int index) { |
311 |
tim |
1.1 |
return entry(index).element; |
312 |
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} |
313 |
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|
314 |
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/** |
315 |
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* Replaces the element at the specified position in this list with the |
316 |
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* specified element. |
317 |
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* |
318 |
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* @param index index of element to replace. |
319 |
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* @param element element to be stored at the specified position. |
320 |
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* @return the element previously at the specified position. |
321 |
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|
* @throws IndexOutOfBoundsException if the specified index is out of |
322 |
jsr166 |
1.14 |
* range (<tt>index < 0 || index >= size()</tt>). |
323 |
tim |
1.1 |
*/ |
324 |
dl |
1.3 |
public E set(int index, E element) { |
325 |
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Entry<E> e = entry(index); |
326 |
|
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E oldVal = e.element; |
327 |
tim |
1.1 |
e.element = element; |
328 |
|
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return oldVal; |
329 |
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} |
330 |
|
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|
331 |
|
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/** |
332 |
|
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* Inserts the specified element at the specified position in this list. |
333 |
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* Shifts the element currently at that position (if any) and any |
334 |
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* subsequent elements to the right (adds one to their indices). |
335 |
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* |
336 |
|
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* @param index index at which the specified element is to be inserted. |
337 |
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* @param element element to be inserted. |
338 |
dl |
1.3 |
* |
339 |
tim |
1.1 |
* @throws IndexOutOfBoundsException if the specified index is out of |
340 |
jsr166 |
1.14 |
* range (<tt>index < 0 || index > size()</tt>). |
341 |
tim |
1.1 |
*/ |
342 |
dl |
1.3 |
public void add(int index, E element) { |
343 |
tim |
1.1 |
addBefore(element, (index==size ? header : entry(index))); |
344 |
|
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} |
345 |
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|
346 |
|
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/** |
347 |
|
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* Removes the element at the specified position in this list. Shifts any |
348 |
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* subsequent elements to the left (subtracts one from their indices). |
349 |
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* Returns the element that was removed from the list. |
350 |
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* |
351 |
|
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* @param index the index of the element to removed. |
352 |
|
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* @return the element previously at the specified position. |
353 |
dl |
1.3 |
* |
354 |
tim |
1.1 |
* @throws IndexOutOfBoundsException if the specified index is out of |
355 |
jsr166 |
1.14 |
* range (<tt>index < 0 || index >= size()</tt>). |
356 |
tim |
1.1 |
*/ |
357 |
dl |
1.3 |
public E remove(int index) { |
358 |
jsr166 |
1.14 |
return remove(entry(index)); |
359 |
tim |
1.1 |
} |
360 |
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|
361 |
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/** |
362 |
|
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* Return the indexed entry. |
363 |
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*/ |
364 |
dl |
1.3 |
private Entry<E> entry(int index) { |
365 |
tim |
1.1 |
if (index < 0 || index >= size) |
366 |
|
|
throw new IndexOutOfBoundsException("Index: "+index+ |
367 |
|
|
", Size: "+size); |
368 |
dl |
1.3 |
Entry<E> e = header; |
369 |
tim |
1.1 |
if (index < (size >> 1)) { |
370 |
|
|
for (int i = 0; i <= index; i++) |
371 |
|
|
e = e.next; |
372 |
|
|
} else { |
373 |
|
|
for (int i = size; i > index; i--) |
374 |
|
|
e = e.previous; |
375 |
|
|
} |
376 |
|
|
return e; |
377 |
|
|
} |
378 |
|
|
|
379 |
|
|
|
380 |
|
|
// Search Operations |
381 |
|
|
|
382 |
|
|
/** |
383 |
|
|
* Returns the index in this list of the first occurrence of the |
384 |
|
|
* specified element, or -1 if the List does not contain this |
385 |
|
|
* element. More formally, returns the lowest index i such that |
386 |
|
|
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, or -1 if |
387 |
|
|
* there is no such index. |
388 |
|
|
* |
389 |
|
|
* @param o element to search for. |
390 |
|
|
* @return the index in this list of the first occurrence of the |
391 |
jsr166 |
1.14 |
* specified element, or -1 if the list does not contain this |
392 |
|
|
* element. |
393 |
tim |
1.1 |
*/ |
394 |
|
|
public int indexOf(Object o) { |
395 |
|
|
int index = 0; |
396 |
|
|
if (o==null) { |
397 |
|
|
for (Entry e = header.next; e != header; e = e.next) { |
398 |
|
|
if (e.element==null) |
399 |
|
|
return index; |
400 |
|
|
index++; |
401 |
|
|
} |
402 |
|
|
} else { |
403 |
|
|
for (Entry e = header.next; e != header; e = e.next) { |
404 |
|
|
if (o.equals(e.element)) |
405 |
|
|
return index; |
406 |
|
|
index++; |
407 |
|
|
} |
408 |
|
|
} |
409 |
|
|
return -1; |
410 |
|
|
} |
411 |
|
|
|
412 |
|
|
/** |
413 |
|
|
* Returns the index in this list of the last occurrence of the |
414 |
|
|
* specified element, or -1 if the list does not contain this |
415 |
|
|
* element. More formally, returns the highest index i such that |
416 |
|
|
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, or -1 if |
417 |
|
|
* there is no such index. |
418 |
|
|
* |
419 |
|
|
* @param o element to search for. |
420 |
|
|
* @return the index in this list of the last occurrence of the |
421 |
jsr166 |
1.14 |
* specified element, or -1 if the list does not contain this |
422 |
|
|
* element. |
423 |
tim |
1.1 |
*/ |
424 |
|
|
public int lastIndexOf(Object o) { |
425 |
|
|
int index = size; |
426 |
|
|
if (o==null) { |
427 |
|
|
for (Entry e = header.previous; e != header; e = e.previous) { |
428 |
|
|
index--; |
429 |
|
|
if (e.element==null) |
430 |
|
|
return index; |
431 |
|
|
} |
432 |
|
|
} else { |
433 |
|
|
for (Entry e = header.previous; e != header; e = e.previous) { |
434 |
|
|
index--; |
435 |
|
|
if (o.equals(e.element)) |
436 |
|
|
return index; |
437 |
|
|
} |
438 |
|
|
} |
439 |
|
|
return -1; |
440 |
|
|
} |
441 |
|
|
|
442 |
dl |
1.3 |
// Queue operations. |
443 |
|
|
|
444 |
|
|
/** |
445 |
dl |
1.7 |
* Retrieves, but does not remove, the head (first element) of this list. |
446 |
dl |
1.19 |
* @return the head of this list, or <tt>null</tt> if this list is empty. |
447 |
dl |
1.7 |
* @since 1.5 |
448 |
dl |
1.3 |
*/ |
449 |
|
|
public E peek() { |
450 |
|
|
if (size==0) |
451 |
|
|
return null; |
452 |
|
|
return getFirst(); |
453 |
|
|
} |
454 |
|
|
|
455 |
|
|
/** |
456 |
dl |
1.7 |
* Retrieves, but does not remove, the head (first element) of this list. |
457 |
dl |
1.19 |
* @return the head of this list. |
458 |
|
|
* @throws NoSuchElementException if this list is empty. |
459 |
dl |
1.7 |
* @since 1.5 |
460 |
dl |
1.3 |
*/ |
461 |
|
|
public E element() { |
462 |
|
|
return getFirst(); |
463 |
|
|
} |
464 |
|
|
|
465 |
|
|
/** |
466 |
dl |
1.7 |
* Retrieves and removes the head (first element) of this list. |
467 |
dl |
1.19 |
* @return the head of this list, or <tt>null</tt> if this list is empty. |
468 |
dl |
1.7 |
* @since 1.5 |
469 |
dl |
1.3 |
*/ |
470 |
|
|
public E poll() { |
471 |
|
|
if (size==0) |
472 |
|
|
return null; |
473 |
|
|
return removeFirst(); |
474 |
|
|
} |
475 |
|
|
|
476 |
|
|
/** |
477 |
dl |
1.7 |
* Retrieves and removes the head (first element) of this list. |
478 |
dl |
1.19 |
* @return the head of this list. |
479 |
|
|
* @throws NoSuchElementException if this list is empty. |
480 |
dl |
1.7 |
* @since 1.5 |
481 |
dl |
1.3 |
*/ |
482 |
|
|
public E remove() { |
483 |
|
|
return removeFirst(); |
484 |
|
|
} |
485 |
|
|
|
486 |
|
|
/** |
487 |
|
|
* Adds the specified element as the tail (last element) of this list. |
488 |
|
|
* |
489 |
jsr166 |
1.11 |
* @param o the element to add. |
490 |
dl |
1.3 |
* @return <tt>true</tt> (as per the general contract of |
491 |
|
|
* <tt>Queue.offer</tt>) |
492 |
dl |
1.7 |
* @since 1.5 |
493 |
dl |
1.3 |
*/ |
494 |
jsr166 |
1.11 |
public boolean offer(E o) { |
495 |
|
|
return add(o); |
496 |
dl |
1.3 |
} |
497 |
|
|
|
498 |
dl |
1.17 |
// Deque operations |
499 |
|
|
/** |
500 |
dl |
1.19 |
* Inserts the specified element to the front of this list. |
501 |
dl |
1.17 |
* |
502 |
dl |
1.21 |
* @param o the element to insert |
503 |
dl |
1.17 |
* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst}) |
504 |
|
|
* @since 1.6 |
505 |
|
|
*/ |
506 |
dl |
1.21 |
public boolean offerFirst(E o) { |
507 |
|
|
addFirst(o); |
508 |
dl |
1.17 |
return true; |
509 |
|
|
} |
510 |
|
|
|
511 |
|
|
/** |
512 |
dl |
1.19 |
* Inserts the specified element to the end of this list. |
513 |
dl |
1.17 |
* |
514 |
dl |
1.21 |
* @param o the element to insert |
515 |
dl |
1.17 |
* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast}) |
516 |
|
|
* @since 1.6 |
517 |
|
|
*/ |
518 |
dl |
1.21 |
public boolean offerLast(E o) { |
519 |
|
|
addLast(o); |
520 |
dl |
1.17 |
return true; |
521 |
|
|
} |
522 |
|
|
|
523 |
|
|
/** |
524 |
dl |
1.19 |
* Retrieves, but does not remove, the first element of this list, |
525 |
|
|
* returning <tt>null</tt> if this list is empty. |
526 |
dl |
1.17 |
* |
527 |
dl |
1.19 |
* @return the first element of this list, or <tt>null</tt> if |
528 |
|
|
* this list is empty |
529 |
dl |
1.17 |
* @since 1.6 |
530 |
|
|
*/ |
531 |
|
|
public E peekFirst() { |
532 |
|
|
if (size==0) |
533 |
|
|
return null; |
534 |
dl |
1.18 |
return getFirst(); |
535 |
dl |
1.17 |
} |
536 |
|
|
|
537 |
|
|
/** |
538 |
dl |
1.19 |
* Retrieves, but does not remove, the last element of this list, |
539 |
|
|
* returning <tt>null</tt> if this list is empty. |
540 |
dl |
1.17 |
* |
541 |
dl |
1.19 |
* @return the last element of this list, or <tt>null</tt> if this list |
542 |
dl |
1.17 |
* is empty |
543 |
|
|
* @since 1.6 |
544 |
|
|
*/ |
545 |
|
|
public E peekLast() { |
546 |
|
|
if (size==0) |
547 |
|
|
return null; |
548 |
dl |
1.18 |
return getLast(); |
549 |
dl |
1.17 |
} |
550 |
|
|
|
551 |
|
|
/** |
552 |
dl |
1.19 |
* Retrieves and removes the first element of this list, or |
553 |
|
|
* <tt>null</tt> if this list is empty. |
554 |
dl |
1.17 |
* |
555 |
dl |
1.19 |
* @return the first element of this list, or <tt>null</tt> if |
556 |
|
|
* this list is empty |
557 |
dl |
1.17 |
* @since 1.6 |
558 |
|
|
*/ |
559 |
|
|
public E pollFirst() { |
560 |
|
|
if (size==0) |
561 |
|
|
return null; |
562 |
|
|
return removeFirst(); |
563 |
|
|
} |
564 |
|
|
|
565 |
|
|
/** |
566 |
dl |
1.19 |
* Retrieves and removes the last element of this list, or |
567 |
|
|
* <tt>null</tt> if this list is empty. |
568 |
dl |
1.17 |
* |
569 |
dl |
1.19 |
* @return the last element of this list, or <tt>null</tt> if |
570 |
|
|
* this list is empty |
571 |
dl |
1.17 |
* @since 1.6 |
572 |
|
|
*/ |
573 |
|
|
public E pollLast() { |
574 |
|
|
if (size==0) |
575 |
|
|
return null; |
576 |
|
|
return removeLast(); |
577 |
|
|
} |
578 |
|
|
|
579 |
|
|
/** |
580 |
dl |
1.19 |
* Pushes an element onto the stack represented by this list. In other |
581 |
dl |
1.20 |
* words, inserts the element to the front of this list. |
582 |
dl |
1.17 |
* |
583 |
|
|
* <p>This method is equivalent to {@link #addFirst}. |
584 |
|
|
* |
585 |
dl |
1.21 |
* @param o the element to push |
586 |
dl |
1.17 |
* @since 1.6 |
587 |
|
|
*/ |
588 |
dl |
1.21 |
public void push(E o) { |
589 |
|
|
addFirst(o); |
590 |
dl |
1.17 |
} |
591 |
|
|
|
592 |
|
|
/** |
593 |
dl |
1.19 |
* Pops an element from the stack represented by this list. In other |
594 |
dl |
1.20 |
* words, removes and returns the first element of this list. |
595 |
dl |
1.17 |
* |
596 |
|
|
* <p>This method is equivalent to {@link #removeFirst()}. |
597 |
|
|
* |
598 |
dl |
1.19 |
* @return the element at the front of this list (which is the top |
599 |
|
|
* of the stack represented by this list) |
600 |
|
|
* @throws NoSuchElementException if this list is empty |
601 |
dl |
1.17 |
* @since 1.6 |
602 |
|
|
*/ |
603 |
|
|
public E pop() { |
604 |
|
|
return removeFirst(); |
605 |
|
|
} |
606 |
|
|
|
607 |
|
|
/** |
608 |
|
|
* Removes the first occurrence of the specified element in this |
609 |
dl |
1.19 |
* list (when traversing the list from head to tail). If the list |
610 |
dl |
1.17 |
* does not contain the element, it is unchanged. |
611 |
|
|
* |
612 |
dl |
1.21 |
* @param o element to be removed from this list, if present |
613 |
dl |
1.19 |
* @return <tt>true</tt> if the list contained the specified element |
614 |
dl |
1.17 |
* @since 1.6 |
615 |
|
|
*/ |
616 |
dl |
1.21 |
public boolean removeFirstOccurrence(Object o) { |
617 |
|
|
return remove(o); |
618 |
dl |
1.17 |
} |
619 |
|
|
|
620 |
|
|
/** |
621 |
|
|
* Removes the last occurrence of the specified element in this |
622 |
dl |
1.19 |
* list (when traversing the list from head to tail). If the list |
623 |
dl |
1.17 |
* does not contain the element, it is unchanged. |
624 |
|
|
* |
625 |
dl |
1.19 |
* @param o element to be removed from this list, if present |
626 |
|
|
* @return <tt>true</tt> if the list contained the specified element |
627 |
dl |
1.17 |
* @since 1.6 |
628 |
|
|
*/ |
629 |
|
|
public boolean removeLastOccurrence(Object o) { |
630 |
|
|
if (o==null) { |
631 |
|
|
for (Entry e = header.previous; e != header; e = e.previous) { |
632 |
|
|
if (e.element==null) { |
633 |
|
|
remove(e); |
634 |
|
|
return true; |
635 |
|
|
} |
636 |
|
|
} |
637 |
|
|
} else { |
638 |
|
|
for (Entry e = header.previous; e != header; e = e.previous) { |
639 |
|
|
if (o.equals(e.element)) { |
640 |
|
|
remove(e); |
641 |
|
|
return true; |
642 |
|
|
} |
643 |
|
|
} |
644 |
|
|
} |
645 |
|
|
return false; |
646 |
|
|
} |
647 |
|
|
|
648 |
tim |
1.1 |
/** |
649 |
|
|
* Returns a list-iterator of the elements in this list (in proper |
650 |
|
|
* sequence), starting at the specified position in the list. |
651 |
|
|
* Obeys the general contract of <tt>List.listIterator(int)</tt>.<p> |
652 |
|
|
* |
653 |
|
|
* The list-iterator is <i>fail-fast</i>: if the list is structurally |
654 |
|
|
* modified at any time after the Iterator is created, in any way except |
655 |
|
|
* through the list-iterator's own <tt>remove</tt> or <tt>add</tt> |
656 |
|
|
* methods, the list-iterator will throw a |
657 |
|
|
* <tt>ConcurrentModificationException</tt>. Thus, in the face of |
658 |
|
|
* concurrent modification, the iterator fails quickly and cleanly, rather |
659 |
|
|
* than risking arbitrary, non-deterministic behavior at an undetermined |
660 |
|
|
* time in the future. |
661 |
|
|
* |
662 |
|
|
* @param index index of first element to be returned from the |
663 |
jsr166 |
1.14 |
* list-iterator (by a call to <tt>next</tt>). |
664 |
tim |
1.1 |
* @return a ListIterator of the elements in this list (in proper |
665 |
jsr166 |
1.14 |
* sequence), starting at the specified position in the list. |
666 |
tim |
1.1 |
* @throws IndexOutOfBoundsException if index is out of range |
667 |
jsr166 |
1.14 |
* (<tt>index < 0 || index > size()</tt>). |
668 |
dl |
1.3 |
* @see List#listIterator(int) |
669 |
tim |
1.1 |
*/ |
670 |
dl |
1.3 |
public ListIterator<E> listIterator(int index) { |
671 |
jsr166 |
1.14 |
return new ListItr(index); |
672 |
tim |
1.1 |
} |
673 |
|
|
|
674 |
dl |
1.3 |
private class ListItr implements ListIterator<E> { |
675 |
jsr166 |
1.14 |
private Entry<E> lastReturned = header; |
676 |
|
|
private Entry<E> next; |
677 |
|
|
private int nextIndex; |
678 |
|
|
private int expectedModCount = modCount; |
679 |
|
|
|
680 |
|
|
ListItr(int index) { |
681 |
|
|
if (index < 0 || index > size) |
682 |
|
|
throw new IndexOutOfBoundsException("Index: "+index+ |
683 |
|
|
", Size: "+size); |
684 |
|
|
if (index < (size >> 1)) { |
685 |
|
|
next = header.next; |
686 |
|
|
for (nextIndex=0; nextIndex<index; nextIndex++) |
687 |
|
|
next = next.next; |
688 |
|
|
} else { |
689 |
|
|
next = header; |
690 |
|
|
for (nextIndex=size; nextIndex>index; nextIndex--) |
691 |
|
|
next = next.previous; |
692 |
|
|
} |
693 |
|
|
} |
694 |
|
|
|
695 |
|
|
public boolean hasNext() { |
696 |
|
|
return nextIndex != size; |
697 |
|
|
} |
698 |
|
|
|
699 |
|
|
public E next() { |
700 |
|
|
checkForComodification(); |
701 |
|
|
if (nextIndex == size) |
702 |
|
|
throw new NoSuchElementException(); |
703 |
|
|
|
704 |
|
|
lastReturned = next; |
705 |
|
|
next = next.next; |
706 |
|
|
nextIndex++; |
707 |
|
|
return lastReturned.element; |
708 |
|
|
} |
709 |
|
|
|
710 |
|
|
public boolean hasPrevious() { |
711 |
|
|
return nextIndex != 0; |
712 |
|
|
} |
713 |
|
|
|
714 |
|
|
public E previous() { |
715 |
|
|
if (nextIndex == 0) |
716 |
|
|
throw new NoSuchElementException(); |
717 |
|
|
|
718 |
|
|
lastReturned = next = next.previous; |
719 |
|
|
nextIndex--; |
720 |
|
|
checkForComodification(); |
721 |
|
|
return lastReturned.element; |
722 |
|
|
} |
723 |
|
|
|
724 |
|
|
public int nextIndex() { |
725 |
|
|
return nextIndex; |
726 |
|
|
} |
727 |
|
|
|
728 |
|
|
public int previousIndex() { |
729 |
|
|
return nextIndex-1; |
730 |
|
|
} |
731 |
jozart |
1.12 |
|
732 |
jsr166 |
1.14 |
public void remove() { |
733 |
tim |
1.1 |
checkForComodification(); |
734 |
jsr166 |
1.14 |
Entry<E> lastNext = lastReturned.next; |
735 |
tim |
1.1 |
try { |
736 |
|
|
LinkedList.this.remove(lastReturned); |
737 |
|
|
} catch (NoSuchElementException e) { |
738 |
|
|
throw new IllegalStateException(); |
739 |
|
|
} |
740 |
jsr166 |
1.14 |
if (next==lastReturned) |
741 |
|
|
next = lastNext; |
742 |
tim |
1.1 |
else |
743 |
jsr166 |
1.14 |
nextIndex--; |
744 |
|
|
lastReturned = header; |
745 |
|
|
expectedModCount++; |
746 |
|
|
} |
747 |
|
|
|
748 |
|
|
public void set(E o) { |
749 |
|
|
if (lastReturned == header) |
750 |
|
|
throw new IllegalStateException(); |
751 |
|
|
checkForComodification(); |
752 |
|
|
lastReturned.element = o; |
753 |
|
|
} |
754 |
|
|
|
755 |
|
|
public void add(E o) { |
756 |
|
|
checkForComodification(); |
757 |
|
|
lastReturned = header; |
758 |
|
|
addBefore(o, next); |
759 |
|
|
nextIndex++; |
760 |
|
|
expectedModCount++; |
761 |
|
|
} |
762 |
|
|
|
763 |
|
|
final void checkForComodification() { |
764 |
|
|
if (modCount != expectedModCount) |
765 |
|
|
throw new ConcurrentModificationException(); |
766 |
|
|
} |
767 |
dl |
1.3 |
} |
768 |
|
|
|
769 |
|
|
private static class Entry<E> { |
770 |
jsr166 |
1.14 |
E element; |
771 |
|
|
Entry<E> next; |
772 |
|
|
Entry<E> previous; |
773 |
|
|
|
774 |
|
|
Entry(E element, Entry<E> next, Entry<E> previous) { |
775 |
|
|
this.element = element; |
776 |
|
|
this.next = next; |
777 |
|
|
this.previous = previous; |
778 |
|
|
} |
779 |
dl |
1.3 |
} |
780 |
|
|
|
781 |
|
|
private Entry<E> addBefore(E o, Entry<E> e) { |
782 |
jsr166 |
1.14 |
Entry<E> newEntry = new Entry<E>(o, e, e.previous); |
783 |
|
|
newEntry.previous.next = newEntry; |
784 |
|
|
newEntry.next.previous = newEntry; |
785 |
|
|
size++; |
786 |
|
|
modCount++; |
787 |
|
|
return newEntry; |
788 |
|
|
} |
789 |
|
|
|
790 |
|
|
private E remove(Entry<E> e) { |
791 |
|
|
if (e == header) |
792 |
|
|
throw new NoSuchElementException(); |
793 |
|
|
|
794 |
|
|
E result = e.element; |
795 |
|
|
e.previous.next = e.next; |
796 |
|
|
e.next.previous = e.previous; |
797 |
|
|
e.next = e.previous = null; |
798 |
|
|
e.element = null; |
799 |
|
|
size--; |
800 |
|
|
modCount++; |
801 |
|
|
return result; |
802 |
tim |
1.1 |
} |
803 |
|
|
|
804 |
|
|
/** |
805 |
|
|
* Returns a shallow copy of this <tt>LinkedList</tt>. (The elements |
806 |
|
|
* themselves are not cloned.) |
807 |
|
|
* |
808 |
|
|
* @return a shallow copy of this <tt>LinkedList</tt> instance. |
809 |
|
|
*/ |
810 |
|
|
public Object clone() { |
811 |
dl |
1.3 |
LinkedList<E> clone = null; |
812 |
jsr166 |
1.14 |
try { |
813 |
|
|
clone = (LinkedList<E>) super.clone(); |
814 |
|
|
} catch (CloneNotSupportedException e) { |
815 |
|
|
throw new InternalError(); |
816 |
|
|
} |
817 |
tim |
1.1 |
|
818 |
|
|
// Put clone into "virgin" state |
819 |
dl |
1.3 |
clone.header = new Entry<E>(null, null, null); |
820 |
tim |
1.1 |
clone.header.next = clone.header.previous = clone.header; |
821 |
|
|
clone.size = 0; |
822 |
|
|
clone.modCount = 0; |
823 |
|
|
|
824 |
|
|
// Initialize clone with our elements |
825 |
dl |
1.3 |
for (Entry<E> e = header.next; e != header; e = e.next) |
826 |
tim |
1.1 |
clone.add(e.element); |
827 |
|
|
|
828 |
|
|
return clone; |
829 |
|
|
} |
830 |
|
|
|
831 |
|
|
/** |
832 |
|
|
* Returns an array containing all of the elements in this list |
833 |
|
|
* in the correct order. |
834 |
|
|
* |
835 |
|
|
* @return an array containing all of the elements in this list |
836 |
jsr166 |
1.14 |
* in the correct order. |
837 |
tim |
1.1 |
*/ |
838 |
|
|
public Object[] toArray() { |
839 |
jsr166 |
1.14 |
Object[] result = new Object[size]; |
840 |
tim |
1.1 |
int i = 0; |
841 |
dl |
1.3 |
for (Entry<E> e = header.next; e != header; e = e.next) |
842 |
tim |
1.1 |
result[i++] = e.element; |
843 |
jsr166 |
1.14 |
return result; |
844 |
tim |
1.1 |
} |
845 |
|
|
|
846 |
|
|
/** |
847 |
|
|
* Returns an array containing all of the elements in this list in |
848 |
|
|
* the correct order; the runtime type of the returned array is that of |
849 |
|
|
* the specified array. If the list fits in the specified array, it |
850 |
|
|
* is returned therein. Otherwise, a new array is allocated with the |
851 |
|
|
* runtime type of the specified array and the size of this list.<p> |
852 |
|
|
* |
853 |
|
|
* If the list fits in the specified array with room to spare |
854 |
|
|
* (i.e., the array has more elements than the list), |
855 |
|
|
* the element in the array immediately following the end of the |
856 |
|
|
* collection is set to null. This is useful in determining the length |
857 |
|
|
* of the list <i>only</i> if the caller knows that the list |
858 |
|
|
* does not contain any null elements. |
859 |
|
|
* |
860 |
|
|
* @param a the array into which the elements of the list are to |
861 |
jsr166 |
1.14 |
* be stored, if it is big enough; otherwise, a new array of the |
862 |
|
|
* same runtime type is allocated for this purpose. |
863 |
tim |
1.1 |
* @return an array containing the elements of the list. |
864 |
|
|
* @throws ArrayStoreException if the runtime type of a is not a |
865 |
|
|
* supertype of the runtime type of every element in this list. |
866 |
|
|
* @throws NullPointerException if the specified array is null. |
867 |
|
|
*/ |
868 |
dl |
1.3 |
public <T> T[] toArray(T[] a) { |
869 |
tim |
1.1 |
if (a.length < size) |
870 |
dl |
1.3 |
a = (T[])java.lang.reflect.Array.newInstance( |
871 |
tim |
1.1 |
a.getClass().getComponentType(), size); |
872 |
|
|
int i = 0; |
873 |
jsr166 |
1.14 |
Object[] result = a; |
874 |
dl |
1.3 |
for (Entry<E> e = header.next; e != header; e = e.next) |
875 |
|
|
result[i++] = e.element; |
876 |
tim |
1.1 |
|
877 |
|
|
if (a.length > size) |
878 |
|
|
a[size] = null; |
879 |
|
|
|
880 |
|
|
return a; |
881 |
|
|
} |
882 |
|
|
|
883 |
|
|
private static final long serialVersionUID = 876323262645176354L; |
884 |
|
|
|
885 |
|
|
/** |
886 |
|
|
* Save the state of this <tt>LinkedList</tt> instance to a stream (that |
887 |
|
|
* is, serialize it). |
888 |
|
|
* |
889 |
|
|
* @serialData The size of the list (the number of elements it |
890 |
jsr166 |
1.14 |
* contains) is emitted (int), followed by all of its |
891 |
dl |
1.3 |
* elements (each an Object) in the proper order. |
892 |
tim |
1.1 |
*/ |
893 |
dl |
1.3 |
private void writeObject(java.io.ObjectOutputStream s) |
894 |
tim |
1.1 |
throws java.io.IOException { |
895 |
jsr166 |
1.14 |
// Write out any hidden serialization magic |
896 |
|
|
s.defaultWriteObject(); |
897 |
tim |
1.1 |
|
898 |
|
|
// Write out size |
899 |
|
|
s.writeInt(size); |
900 |
|
|
|
901 |
jsr166 |
1.14 |
// Write out all elements in the proper order. |
902 |
tim |
1.1 |
for (Entry e = header.next; e != header; e = e.next) |
903 |
|
|
s.writeObject(e.element); |
904 |
|
|
} |
905 |
|
|
|
906 |
|
|
/** |
907 |
|
|
* Reconstitute this <tt>LinkedList</tt> instance from a stream (that is |
908 |
|
|
* deserialize it). |
909 |
|
|
*/ |
910 |
dl |
1.3 |
private void readObject(java.io.ObjectInputStream s) |
911 |
tim |
1.1 |
throws java.io.IOException, ClassNotFoundException { |
912 |
jsr166 |
1.14 |
// Read in any hidden serialization magic |
913 |
|
|
s.defaultReadObject(); |
914 |
tim |
1.1 |
|
915 |
|
|
// Read in size |
916 |
|
|
int size = s.readInt(); |
917 |
|
|
|
918 |
|
|
// Initialize header |
919 |
dl |
1.3 |
header = new Entry<E>(null, null, null); |
920 |
tim |
1.1 |
header.next = header.previous = header; |
921 |
|
|
|
922 |
jsr166 |
1.14 |
// Read in all elements in the proper order. |
923 |
|
|
for (int i=0; i<size; i++) |
924 |
dl |
1.3 |
addBefore((E)s.readObject(), header); |
925 |
tim |
1.1 |
} |
926 |
|
|
} |