1 |
tim |
1.1 |
/* |
2 |
dl |
1.6 |
* %W% %E% |
3 |
tim |
1.1 |
* |
4 |
dl |
1.3 |
* Copyright 2003 Sun Microsystems, Inc. All rights reserved. |
5 |
tim |
1.1 |
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
6 |
|
|
*/ |
7 |
|
|
|
8 |
|
|
package java.util; |
9 |
|
|
|
10 |
|
|
/** |
11 |
|
|
* Linked list implementation of the <tt>List</tt> interface. Implements all |
12 |
|
|
* optional list operations, and permits all elements (including |
13 |
|
|
* <tt>null</tt>). In addition to implementing the <tt>List</tt> interface, |
14 |
|
|
* the <tt>LinkedList</tt> class provides uniformly named methods to |
15 |
|
|
* <tt>get</tt>, <tt>remove</tt> and <tt>insert</tt> an element at the |
16 |
|
|
* beginning and end of the list. These operations allow linked lists to be |
17 |
|
|
* used as a stack, queue, or double-ended queue (deque).<p> |
18 |
|
|
* |
19 |
dl |
1.3 |
* The class implements the <tt>Queue</tt> interface, providing |
20 |
|
|
* first-in-first-out queue operations for <tt>add</tt>, |
21 |
|
|
* <tt>poll</tt>, etc. Other stack and deque operations could be |
22 |
|
|
* easily recast in terms of the standard list operations. They're |
23 |
|
|
* included here primarily for convenience, though they may run |
24 |
|
|
* slightly faster than the equivalent List operations.<p> |
25 |
tim |
1.1 |
* |
26 |
|
|
* All of the operations perform as could be expected for a doubly-linked |
27 |
|
|
* list. Operations that index into the list will traverse the list from |
28 |
|
|
* the begining or the end, whichever is closer to the specified index.<p> |
29 |
|
|
* |
30 |
|
|
* <b>Note that this implementation is not synchronized.</b> If multiple |
31 |
|
|
* threads access a list concurrently, and at least one of the threads |
32 |
|
|
* modifies the list structurally, it <i>must</i> be synchronized |
33 |
|
|
* externally. (A structural modification is any operation that adds or |
34 |
|
|
* deletes one or more elements; merely setting the value of an element is not |
35 |
|
|
* a structural modification.) This is typically accomplished by |
36 |
|
|
* synchronizing on some object that naturally encapsulates the list. If no |
37 |
|
|
* such object exists, the list should be "wrapped" using the |
38 |
|
|
* Collections.synchronizedList method. This is best done at creation time, |
39 |
|
|
* to prevent accidental unsynchronized access to the list: <pre> |
40 |
|
|
* List list = Collections.synchronizedList(new LinkedList(...)); |
41 |
|
|
* </pre><p> |
42 |
|
|
* |
43 |
|
|
* The iterators returned by the this class's <tt>iterator</tt> and |
44 |
|
|
* <tt>listIterator</tt> methods are <i>fail-fast</i>: if the list is |
45 |
|
|
* structurally modified at any time after the iterator is created, in any way |
46 |
|
|
* except through the Iterator's own <tt>remove</tt> or <tt>add</tt> methods, |
47 |
|
|
* the iterator will throw a <tt>ConcurrentModificationException</tt>. Thus, |
48 |
|
|
* in the face of concurrent modification, the iterator fails quickly and |
49 |
|
|
* cleanly, rather than risking arbitrary, non-deterministic behavior at an |
50 |
|
|
* undetermined time in the future. |
51 |
|
|
* |
52 |
|
|
* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
53 |
|
|
* as it is, generally speaking, impossible to make any hard guarantees in the |
54 |
|
|
* presence of unsynchronized concurrent modification. Fail-fast iterators |
55 |
dl |
1.3 |
* throw <tt>ConcurrentModificationException</tt> on a best-effort basis. |
56 |
tim |
1.1 |
* Therefore, it would be wrong to write a program that depended on this |
57 |
|
|
* exception for its correctness: <i>the fail-fast behavior of iterators |
58 |
dl |
1.3 |
* should be used only to detect bugs.</i><p> |
59 |
|
|
* |
60 |
|
|
* This class is a member of the |
61 |
|
|
* <a href="{@docRoot}/../guide/collections/index.html"> |
62 |
|
|
* Java Collections Framework</a>. |
63 |
tim |
1.1 |
* |
64 |
|
|
* @author Josh Bloch |
65 |
dl |
1.6 |
* @version %I%, %G% |
66 |
dl |
1.3 |
* @see List |
67 |
|
|
* @see ArrayList |
68 |
|
|
* @see Vector |
69 |
|
|
* @see Collections#synchronizedList(List) |
70 |
tim |
1.1 |
* @since 1.2 |
71 |
|
|
*/ |
72 |
|
|
|
73 |
dl |
1.3 |
public class LinkedList<E> |
74 |
|
|
extends AbstractSequentialList<E> |
75 |
|
|
implements List<E>, Queue<E>, Cloneable, java.io.Serializable |
76 |
tim |
1.1 |
{ |
77 |
dl |
1.3 |
private transient Entry<E> header = new Entry<E>(null, null, null); |
78 |
tim |
1.1 |
private transient int size = 0; |
79 |
|
|
|
80 |
|
|
/** |
81 |
|
|
* Constructs an empty list. |
82 |
|
|
*/ |
83 |
|
|
public LinkedList() { |
84 |
|
|
header.next = header.previous = header; |
85 |
|
|
} |
86 |
|
|
|
87 |
|
|
/** |
88 |
|
|
* Constructs a list containing the elements of the specified |
89 |
|
|
* collection, in the order they are returned by the collection's |
90 |
|
|
* iterator. |
91 |
|
|
* |
92 |
|
|
* @param c the collection whose elements are to be placed into this list. |
93 |
|
|
* @throws NullPointerException if the specified collection is null. |
94 |
|
|
*/ |
95 |
dl |
1.3 |
public LinkedList(Collection<? extends E> c) { |
96 |
|
|
this(); |
97 |
|
|
addAll(c); |
98 |
tim |
1.1 |
} |
99 |
|
|
|
100 |
|
|
/** |
101 |
|
|
* Returns the first element in this list. |
102 |
|
|
* |
103 |
|
|
* @return the first element in this list. |
104 |
|
|
* @throws NoSuchElementException if this list is empty. |
105 |
|
|
*/ |
106 |
dl |
1.3 |
public E getFirst() { |
107 |
|
|
if (size==0) |
108 |
|
|
throw new NoSuchElementException(); |
109 |
tim |
1.1 |
|
110 |
dl |
1.3 |
return header.next.element; |
111 |
tim |
1.1 |
} |
112 |
|
|
|
113 |
|
|
/** |
114 |
|
|
* Returns the last element in this list. |
115 |
|
|
* |
116 |
|
|
* @return the last element in this list. |
117 |
|
|
* @throws NoSuchElementException if this list is empty. |
118 |
|
|
*/ |
119 |
dl |
1.3 |
public E getLast() { |
120 |
|
|
if (size==0) |
121 |
|
|
throw new NoSuchElementException(); |
122 |
tim |
1.1 |
|
123 |
dl |
1.3 |
return header.previous.element; |
124 |
tim |
1.1 |
} |
125 |
|
|
|
126 |
|
|
/** |
127 |
|
|
* Removes and returns the first element from this list. |
128 |
|
|
* |
129 |
|
|
* @return the first element from this list. |
130 |
|
|
* @throws NoSuchElementException if this list is empty. |
131 |
|
|
*/ |
132 |
dl |
1.3 |
public E removeFirst() { |
133 |
|
|
E first = header.next.element; |
134 |
|
|
remove(header.next); |
135 |
|
|
return first; |
136 |
tim |
1.1 |
} |
137 |
|
|
|
138 |
|
|
/** |
139 |
|
|
* Removes and returns the last element from this list. |
140 |
|
|
* |
141 |
|
|
* @return the last element from this list. |
142 |
|
|
* @throws NoSuchElementException if this list is empty. |
143 |
|
|
*/ |
144 |
dl |
1.3 |
public E removeLast() { |
145 |
|
|
E last = header.previous.element; |
146 |
|
|
remove(header.previous); |
147 |
|
|
return last; |
148 |
tim |
1.1 |
} |
149 |
|
|
|
150 |
|
|
/** |
151 |
|
|
* Inserts the given element at the beginning of this list. |
152 |
dl |
1.3 |
* |
153 |
tim |
1.1 |
* @param o the element to be inserted at the beginning of this list. |
154 |
|
|
*/ |
155 |
dl |
1.3 |
public void addFirst(E o) { |
156 |
|
|
addBefore(o, header.next); |
157 |
tim |
1.1 |
} |
158 |
|
|
|
159 |
|
|
/** |
160 |
|
|
* Appends the given element to the end of this list. (Identical in |
161 |
|
|
* function to the <tt>add</tt> method; included only for consistency.) |
162 |
dl |
1.3 |
* |
163 |
tim |
1.1 |
* @param o the element to be inserted at the end of this list. |
164 |
|
|
*/ |
165 |
dl |
1.3 |
public void addLast(E o) { |
166 |
|
|
addBefore(o, header); |
167 |
tim |
1.1 |
} |
168 |
|
|
|
169 |
|
|
/** |
170 |
|
|
* Returns <tt>true</tt> if this list contains the specified element. |
171 |
|
|
* More formally, returns <tt>true</tt> if and only if this list contains |
172 |
|
|
* at least one element <tt>e</tt> such that <tt>(o==null ? e==null |
173 |
|
|
* : o.equals(e))</tt>. |
174 |
|
|
* |
175 |
|
|
* @param o element whose presence in this list is to be tested. |
176 |
|
|
* @return <tt>true</tt> if this list contains the specified element. |
177 |
|
|
*/ |
178 |
|
|
public boolean contains(Object o) { |
179 |
|
|
return indexOf(o) != -1; |
180 |
|
|
} |
181 |
|
|
|
182 |
|
|
/** |
183 |
|
|
* Returns the number of elements in this list. |
184 |
|
|
* |
185 |
|
|
* @return the number of elements in this list. |
186 |
|
|
*/ |
187 |
|
|
public int size() { |
188 |
dl |
1.3 |
return size; |
189 |
tim |
1.1 |
} |
190 |
|
|
|
191 |
|
|
/** |
192 |
|
|
* Appends the specified element to the end of this list. |
193 |
|
|
* |
194 |
|
|
* @param o element to be appended to this list. |
195 |
|
|
* @return <tt>true</tt> (as per the general contract of |
196 |
|
|
* <tt>Collection.add</tt>). |
197 |
|
|
*/ |
198 |
dl |
1.3 |
public boolean add(E o) { |
199 |
|
|
addBefore(o, header); |
200 |
tim |
1.1 |
return true; |
201 |
|
|
} |
202 |
|
|
|
203 |
|
|
/** |
204 |
|
|
* Removes the first occurrence of the specified element in this list. If |
205 |
|
|
* the list does not contain the element, it is unchanged. More formally, |
206 |
|
|
* removes the element with the lowest index <tt>i</tt> such that |
207 |
|
|
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> (if such an |
208 |
|
|
* element exists). |
209 |
|
|
* |
210 |
|
|
* @param o element to be removed from this list, if present. |
211 |
|
|
* @return <tt>true</tt> if the list contained the specified element. |
212 |
|
|
*/ |
213 |
|
|
public boolean remove(Object o) { |
214 |
|
|
if (o==null) { |
215 |
dl |
1.3 |
for (Entry<E> e = header.next; e != header; e = e.next) { |
216 |
tim |
1.1 |
if (e.element==null) { |
217 |
|
|
remove(e); |
218 |
|
|
return true; |
219 |
|
|
} |
220 |
|
|
} |
221 |
|
|
} else { |
222 |
dl |
1.3 |
for (Entry<E> e = header.next; e != header; e = e.next) { |
223 |
tim |
1.1 |
if (o.equals(e.element)) { |
224 |
|
|
remove(e); |
225 |
|
|
return true; |
226 |
|
|
} |
227 |
|
|
} |
228 |
|
|
} |
229 |
|
|
return false; |
230 |
|
|
} |
231 |
|
|
|
232 |
|
|
/** |
233 |
|
|
* Appends all of the elements in the specified collection to the end of |
234 |
|
|
* this list, in the order that they are returned by the specified |
235 |
|
|
* collection's iterator. The behavior of this operation is undefined if |
236 |
|
|
* the specified collection is modified while the operation is in |
237 |
|
|
* progress. (This implies that the behavior of this call is undefined if |
238 |
|
|
* the specified Collection is this list, and this list is nonempty.) |
239 |
|
|
* |
240 |
|
|
* @param c the elements to be inserted into this list. |
241 |
|
|
* @return <tt>true</tt> if this list changed as a result of the call. |
242 |
|
|
* @throws NullPointerException if the specified collection is null. |
243 |
|
|
*/ |
244 |
dl |
1.3 |
public boolean addAll(Collection<? extends E> c) { |
245 |
tim |
1.1 |
return addAll(size, c); |
246 |
|
|
} |
247 |
|
|
|
248 |
|
|
/** |
249 |
|
|
* Inserts all of the elements in the specified collection into this |
250 |
|
|
* list, starting at the specified position. Shifts the element |
251 |
|
|
* currently at that position (if any) and any subsequent elements to |
252 |
|
|
* the right (increases their indices). The new elements will appear |
253 |
|
|
* in the list in the order that they are returned by the |
254 |
|
|
* specified collection's iterator. |
255 |
|
|
* |
256 |
|
|
* @param index index at which to insert first element |
257 |
dl |
1.3 |
* from the specified collection. |
258 |
tim |
1.1 |
* @param c elements to be inserted into this list. |
259 |
|
|
* @return <tt>true</tt> if this list changed as a result of the call. |
260 |
|
|
* @throws IndexOutOfBoundsException if the specified index is out of |
261 |
|
|
* range (<tt>index < 0 || index > size()</tt>). |
262 |
|
|
* @throws NullPointerException if the specified collection is null. |
263 |
|
|
*/ |
264 |
dl |
1.3 |
public boolean addAll(int index, Collection<? extends E> c) { |
265 |
dl |
1.4 |
if (index < 0 || index > size) |
266 |
dl |
1.3 |
throw new IndexOutOfBoundsException("Index: "+index+ |
267 |
|
|
", Size: "+size); |
268 |
|
|
Object[] a = c.toArray(); |
269 |
|
|
int numNew = a.length; |
270 |
|
|
if (numNew==0) |
271 |
|
|
return false; |
272 |
|
|
modCount++; |
273 |
|
|
|
274 |
|
|
Entry<E> successor = (index==size ? header : entry(index)); |
275 |
|
|
Entry<E> predecessor = successor.previous; |
276 |
|
|
for (int i=0; i<numNew; i++) { |
277 |
|
|
Entry<E> e = new Entry<E>((E)a[i], successor, predecessor); |
278 |
tim |
1.1 |
predecessor.next = e; |
279 |
|
|
predecessor = e; |
280 |
|
|
} |
281 |
|
|
successor.previous = predecessor; |
282 |
|
|
|
283 |
|
|
size += numNew; |
284 |
|
|
return true; |
285 |
|
|
} |
286 |
|
|
|
287 |
|
|
/** |
288 |
|
|
* Removes all of the elements from this list. |
289 |
|
|
*/ |
290 |
|
|
public void clear() { |
291 |
dl |
1.3 |
modCount++; |
292 |
tim |
1.1 |
header.next = header.previous = header; |
293 |
dl |
1.3 |
size = 0; |
294 |
tim |
1.1 |
} |
295 |
|
|
|
296 |
|
|
|
297 |
|
|
// Positional Access Operations |
298 |
|
|
|
299 |
|
|
/** |
300 |
|
|
* Returns the element at the specified position in this list. |
301 |
|
|
* |
302 |
|
|
* @param index index of element to return. |
303 |
|
|
* @return the element at the specified position in this list. |
304 |
dl |
1.3 |
* |
305 |
tim |
1.1 |
* @throws IndexOutOfBoundsException if the specified index is is out of |
306 |
|
|
* range (<tt>index < 0 || index >= size()</tt>). |
307 |
|
|
*/ |
308 |
dl |
1.3 |
public E get(int index) { |
309 |
tim |
1.1 |
return entry(index).element; |
310 |
|
|
} |
311 |
|
|
|
312 |
|
|
/** |
313 |
|
|
* Replaces the element at the specified position in this list with the |
314 |
|
|
* specified element. |
315 |
|
|
* |
316 |
|
|
* @param index index of element to replace. |
317 |
|
|
* @param element element to be stored at the specified position. |
318 |
|
|
* @return the element previously at the specified position. |
319 |
|
|
* @throws IndexOutOfBoundsException if the specified index is out of |
320 |
dl |
1.3 |
* range (<tt>index < 0 || index >= size()</tt>). |
321 |
tim |
1.1 |
*/ |
322 |
dl |
1.3 |
public E set(int index, E element) { |
323 |
|
|
Entry<E> e = entry(index); |
324 |
|
|
E oldVal = e.element; |
325 |
tim |
1.1 |
e.element = element; |
326 |
|
|
return oldVal; |
327 |
|
|
} |
328 |
|
|
|
329 |
|
|
/** |
330 |
|
|
* Inserts the specified element at the specified position in this list. |
331 |
|
|
* Shifts the element currently at that position (if any) and any |
332 |
|
|
* subsequent elements to the right (adds one to their indices). |
333 |
|
|
* |
334 |
|
|
* @param index index at which the specified element is to be inserted. |
335 |
|
|
* @param element element to be inserted. |
336 |
dl |
1.3 |
* |
337 |
tim |
1.1 |
* @throws IndexOutOfBoundsException if the specified index is out of |
338 |
dl |
1.3 |
* range (<tt>index < 0 || index > size()</tt>). |
339 |
tim |
1.1 |
*/ |
340 |
dl |
1.3 |
public void add(int index, E element) { |
341 |
tim |
1.1 |
addBefore(element, (index==size ? header : entry(index))); |
342 |
|
|
} |
343 |
|
|
|
344 |
|
|
/** |
345 |
|
|
* Removes the element at the specified position in this list. Shifts any |
346 |
|
|
* subsequent elements to the left (subtracts one from their indices). |
347 |
|
|
* Returns the element that was removed from the list. |
348 |
|
|
* |
349 |
|
|
* @param index the index of the element to removed. |
350 |
|
|
* @return the element previously at the specified position. |
351 |
dl |
1.3 |
* |
352 |
tim |
1.1 |
* @throws IndexOutOfBoundsException if the specified index is out of |
353 |
dl |
1.3 |
* range (<tt>index < 0 || index >= size()</tt>). |
354 |
tim |
1.1 |
*/ |
355 |
dl |
1.3 |
public E remove(int index) { |
356 |
|
|
Entry<E> e = entry(index); |
357 |
tim |
1.1 |
remove(e); |
358 |
|
|
return e.element; |
359 |
|
|
} |
360 |
|
|
|
361 |
|
|
/** |
362 |
|
|
* Return the indexed entry. |
363 |
|
|
*/ |
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 |
dl |
1.3 |
* 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 |
dl |
1.3 |
* 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 |
|
|
* Retrieves, but does not remove, the head (first element) of this list.. |
446 |
|
|
* @return the head of this queue, or <tt>null</tt> if this queue is empty. |
447 |
|
|
*/ |
448 |
|
|
public E peek() { |
449 |
|
|
if (size==0) |
450 |
|
|
return null; |
451 |
|
|
return getFirst(); |
452 |
|
|
} |
453 |
|
|
|
454 |
|
|
/** |
455 |
|
|
* Retrieves, but does not remove, the head (first element) of this list.. |
456 |
|
|
* @return the head of this queue. |
457 |
|
|
* @throws NoSuchElementException if this queue is empty. |
458 |
|
|
*/ |
459 |
|
|
public E element() { |
460 |
|
|
return getFirst(); |
461 |
|
|
} |
462 |
|
|
|
463 |
|
|
/** |
464 |
|
|
* Retrieves and removes the head (first element) of this list.. |
465 |
|
|
* @return the head of this queue, or <tt>null</tt> if this queue is empty. |
466 |
|
|
*/ |
467 |
|
|
public E poll() { |
468 |
|
|
if (size==0) |
469 |
|
|
return null; |
470 |
|
|
return removeFirst(); |
471 |
|
|
} |
472 |
|
|
|
473 |
|
|
/** |
474 |
|
|
* Retrieves and removes the head (first element) of this list.. |
475 |
|
|
* @return the head of this queue. |
476 |
|
|
* @throws NoSuchElementException if this queue is empty. |
477 |
|
|
*/ |
478 |
|
|
public E remove() { |
479 |
|
|
return removeFirst(); |
480 |
|
|
} |
481 |
|
|
|
482 |
|
|
/** |
483 |
|
|
* Adds the specified element as the tail (last element) of this list. |
484 |
|
|
* |
485 |
dl |
1.5 |
* @param x the element to add. |
486 |
dl |
1.3 |
* @return <tt>true</tt> (as per the general contract of |
487 |
|
|
* <tt>Queue.offer</tt>) |
488 |
|
|
*/ |
489 |
|
|
public boolean offer(E x) { |
490 |
|
|
return add(x); |
491 |
|
|
} |
492 |
|
|
|
493 |
tim |
1.1 |
/** |
494 |
|
|
* Returns a list-iterator of the elements in this list (in proper |
495 |
|
|
* sequence), starting at the specified position in the list. |
496 |
|
|
* Obeys the general contract of <tt>List.listIterator(int)</tt>.<p> |
497 |
|
|
* |
498 |
|
|
* The list-iterator is <i>fail-fast</i>: if the list is structurally |
499 |
|
|
* modified at any time after the Iterator is created, in any way except |
500 |
|
|
* through the list-iterator's own <tt>remove</tt> or <tt>add</tt> |
501 |
|
|
* methods, the list-iterator will throw a |
502 |
|
|
* <tt>ConcurrentModificationException</tt>. Thus, in the face of |
503 |
|
|
* concurrent modification, the iterator fails quickly and cleanly, rather |
504 |
|
|
* than risking arbitrary, non-deterministic behavior at an undetermined |
505 |
|
|
* time in the future. |
506 |
|
|
* |
507 |
|
|
* @param index index of first element to be returned from the |
508 |
dl |
1.3 |
* list-iterator (by a call to <tt>next</tt>). |
509 |
tim |
1.1 |
* @return a ListIterator of the elements in this list (in proper |
510 |
dl |
1.3 |
* sequence), starting at the specified position in the list. |
511 |
tim |
1.1 |
* @throws IndexOutOfBoundsException if index is out of range |
512 |
dl |
1.3 |
* (<tt>index < 0 || index > size()</tt>). |
513 |
|
|
* @see List#listIterator(int) |
514 |
tim |
1.1 |
*/ |
515 |
dl |
1.3 |
public ListIterator<E> listIterator(int index) { |
516 |
|
|
return new ListItr(index); |
517 |
tim |
1.1 |
} |
518 |
|
|
|
519 |
dl |
1.3 |
private class ListItr implements ListIterator<E> { |
520 |
|
|
private Entry<E> lastReturned = header; |
521 |
|
|
private Entry<E> next; |
522 |
|
|
private int nextIndex; |
523 |
|
|
private int expectedModCount = modCount; |
524 |
|
|
|
525 |
|
|
ListItr(int index) { |
526 |
|
|
if (index < 0 || index > size) |
527 |
|
|
throw new IndexOutOfBoundsException("Index: "+index+ |
528 |
|
|
", Size: "+size); |
529 |
|
|
if (index < (size >> 1)) { |
530 |
|
|
next = header.next; |
531 |
|
|
for (nextIndex=0; nextIndex<index; nextIndex++) |
532 |
|
|
next = next.next; |
533 |
|
|
} else { |
534 |
|
|
next = header; |
535 |
|
|
for (nextIndex=size; nextIndex>index; nextIndex--) |
536 |
|
|
next = next.previous; |
537 |
|
|
} |
538 |
|
|
} |
539 |
|
|
|
540 |
|
|
public boolean hasNext() { |
541 |
|
|
return nextIndex != size; |
542 |
|
|
} |
543 |
|
|
|
544 |
|
|
public E next() { |
545 |
|
|
checkForComodification(); |
546 |
|
|
if (nextIndex == size) |
547 |
|
|
throw new NoSuchElementException(); |
548 |
|
|
|
549 |
|
|
lastReturned = next; |
550 |
|
|
next = next.next; |
551 |
|
|
nextIndex++; |
552 |
|
|
return lastReturned.element; |
553 |
|
|
} |
554 |
|
|
|
555 |
|
|
public boolean hasPrevious() { |
556 |
|
|
return nextIndex != 0; |
557 |
|
|
} |
558 |
|
|
|
559 |
|
|
public E previous() { |
560 |
|
|
if (nextIndex == 0) |
561 |
|
|
throw new NoSuchElementException(); |
562 |
|
|
|
563 |
|
|
lastReturned = next = next.previous; |
564 |
|
|
nextIndex--; |
565 |
|
|
checkForComodification(); |
566 |
|
|
return lastReturned.element; |
567 |
|
|
} |
568 |
|
|
|
569 |
|
|
public int nextIndex() { |
570 |
|
|
return nextIndex; |
571 |
|
|
} |
572 |
|
|
|
573 |
|
|
public int previousIndex() { |
574 |
|
|
return nextIndex-1; |
575 |
|
|
} |
576 |
tim |
1.1 |
|
577 |
dl |
1.3 |
public void remove() { |
578 |
tim |
1.1 |
checkForComodification(); |
579 |
|
|
try { |
580 |
|
|
LinkedList.this.remove(lastReturned); |
581 |
|
|
} catch (NoSuchElementException e) { |
582 |
|
|
throw new IllegalStateException(); |
583 |
|
|
} |
584 |
dl |
1.3 |
if (next==lastReturned) |
585 |
tim |
1.1 |
next = lastReturned.next; |
586 |
|
|
else |
587 |
dl |
1.3 |
nextIndex--; |
588 |
|
|
lastReturned = header; |
589 |
|
|
expectedModCount++; |
590 |
|
|
} |
591 |
|
|
|
592 |
|
|
public void set(E o) { |
593 |
|
|
if (lastReturned == header) |
594 |
|
|
throw new IllegalStateException(); |
595 |
|
|
checkForComodification(); |
596 |
|
|
lastReturned.element = o; |
597 |
|
|
} |
598 |
|
|
|
599 |
|
|
public void add(E o) { |
600 |
|
|
checkForComodification(); |
601 |
|
|
lastReturned = header; |
602 |
|
|
addBefore(o, next); |
603 |
|
|
nextIndex++; |
604 |
|
|
expectedModCount++; |
605 |
|
|
} |
606 |
|
|
|
607 |
|
|
final void checkForComodification() { |
608 |
|
|
if (modCount != expectedModCount) |
609 |
|
|
throw new ConcurrentModificationException(); |
610 |
|
|
} |
611 |
|
|
} |
612 |
|
|
|
613 |
|
|
private static class Entry<E> { |
614 |
|
|
E element; |
615 |
|
|
Entry<E> next; |
616 |
|
|
Entry<E> previous; |
617 |
|
|
|
618 |
|
|
Entry(E element, Entry<E> next, Entry<E> previous) { |
619 |
|
|
this.element = element; |
620 |
|
|
this.next = next; |
621 |
|
|
this.previous = previous; |
622 |
|
|
} |
623 |
|
|
} |
624 |
|
|
|
625 |
|
|
private Entry<E> addBefore(E o, Entry<E> e) { |
626 |
|
|
Entry<E> newEntry = new Entry<E>(o, e, e.previous); |
627 |
|
|
newEntry.previous.next = newEntry; |
628 |
|
|
newEntry.next.previous = newEntry; |
629 |
|
|
size++; |
630 |
|
|
modCount++; |
631 |
|
|
return newEntry; |
632 |
|
|
} |
633 |
|
|
|
634 |
|
|
private void remove(Entry<E> e) { |
635 |
|
|
if (e == header) |
636 |
|
|
throw new NoSuchElementException(); |
637 |
|
|
|
638 |
|
|
e.previous.next = e.next; |
639 |
|
|
e.next.previous = e.previous; |
640 |
|
|
size--; |
641 |
|
|
modCount++; |
642 |
tim |
1.1 |
} |
643 |
|
|
|
644 |
|
|
/** |
645 |
|
|
* Returns a shallow copy of this <tt>LinkedList</tt>. (The elements |
646 |
|
|
* themselves are not cloned.) |
647 |
|
|
* |
648 |
|
|
* @return a shallow copy of this <tt>LinkedList</tt> instance. |
649 |
|
|
*/ |
650 |
|
|
public Object clone() { |
651 |
dl |
1.3 |
LinkedList<E> clone = null; |
652 |
|
|
try { |
653 |
|
|
clone = (LinkedList<E>) super.clone(); |
654 |
|
|
} catch (CloneNotSupportedException e) { |
655 |
|
|
throw new InternalError(); |
656 |
|
|
} |
657 |
tim |
1.1 |
|
658 |
|
|
// Put clone into "virgin" state |
659 |
dl |
1.3 |
clone.header = new Entry<E>(null, null, null); |
660 |
tim |
1.1 |
clone.header.next = clone.header.previous = clone.header; |
661 |
|
|
clone.size = 0; |
662 |
|
|
clone.modCount = 0; |
663 |
|
|
|
664 |
|
|
// Initialize clone with our elements |
665 |
dl |
1.3 |
for (Entry<E> e = header.next; e != header; e = e.next) |
666 |
tim |
1.1 |
clone.add(e.element); |
667 |
|
|
|
668 |
|
|
return clone; |
669 |
|
|
} |
670 |
|
|
|
671 |
|
|
/** |
672 |
|
|
* Returns an array containing all of the elements in this list |
673 |
|
|
* in the correct order. |
674 |
|
|
* |
675 |
|
|
* @return an array containing all of the elements in this list |
676 |
dl |
1.3 |
* in the correct order. |
677 |
tim |
1.1 |
*/ |
678 |
|
|
public Object[] toArray() { |
679 |
dl |
1.3 |
Object[] result = new Object[size]; |
680 |
tim |
1.1 |
int i = 0; |
681 |
dl |
1.3 |
for (Entry<E> e = header.next; e != header; e = e.next) |
682 |
tim |
1.1 |
result[i++] = e.element; |
683 |
dl |
1.3 |
return result; |
684 |
tim |
1.1 |
} |
685 |
|
|
|
686 |
|
|
/** |
687 |
|
|
* Returns an array containing all of the elements in this list in |
688 |
|
|
* the correct order; the runtime type of the returned array is that of |
689 |
|
|
* the specified array. If the list fits in the specified array, it |
690 |
|
|
* is returned therein. Otherwise, a new array is allocated with the |
691 |
|
|
* runtime type of the specified array and the size of this list.<p> |
692 |
|
|
* |
693 |
|
|
* If the list fits in the specified array with room to spare |
694 |
|
|
* (i.e., the array has more elements than the list), |
695 |
|
|
* the element in the array immediately following the end of the |
696 |
|
|
* collection is set to null. This is useful in determining the length |
697 |
|
|
* of the list <i>only</i> if the caller knows that the list |
698 |
|
|
* does not contain any null elements. |
699 |
|
|
* |
700 |
|
|
* @param a the array into which the elements of the list are to |
701 |
dl |
1.3 |
* be stored, if it is big enough; otherwise, a new array of the |
702 |
|
|
* same runtime type is allocated for this purpose. |
703 |
tim |
1.1 |
* @return an array containing the elements of the list. |
704 |
|
|
* @throws ArrayStoreException if the runtime type of a is not a |
705 |
|
|
* supertype of the runtime type of every element in this list. |
706 |
|
|
* @throws NullPointerException if the specified array is null. |
707 |
|
|
*/ |
708 |
dl |
1.3 |
public <T> T[] toArray(T[] a) { |
709 |
tim |
1.1 |
if (a.length < size) |
710 |
dl |
1.3 |
a = (T[])java.lang.reflect.Array.newInstance( |
711 |
tim |
1.1 |
a.getClass().getComponentType(), size); |
712 |
|
|
int i = 0; |
713 |
dl |
1.3 |
Object[] result = a; |
714 |
|
|
for (Entry<E> e = header.next; e != header; e = e.next) |
715 |
|
|
result[i++] = e.element; |
716 |
tim |
1.1 |
|
717 |
|
|
if (a.length > size) |
718 |
|
|
a[size] = null; |
719 |
|
|
|
720 |
|
|
return a; |
721 |
|
|
} |
722 |
|
|
|
723 |
|
|
private static final long serialVersionUID = 876323262645176354L; |
724 |
|
|
|
725 |
|
|
/** |
726 |
|
|
* Save the state of this <tt>LinkedList</tt> instance to a stream (that |
727 |
|
|
* is, serialize it). |
728 |
|
|
* |
729 |
|
|
* @serialData The size of the list (the number of elements it |
730 |
dl |
1.3 |
* contains) is emitted (int), followed by all of its |
731 |
|
|
* elements (each an Object) in the proper order. |
732 |
tim |
1.1 |
*/ |
733 |
dl |
1.3 |
private void writeObject(java.io.ObjectOutputStream s) |
734 |
tim |
1.1 |
throws java.io.IOException { |
735 |
dl |
1.3 |
// Write out any hidden serialization magic |
736 |
|
|
s.defaultWriteObject(); |
737 |
tim |
1.1 |
|
738 |
|
|
// Write out size |
739 |
|
|
s.writeInt(size); |
740 |
|
|
|
741 |
dl |
1.3 |
// Write out all elements in the proper order. |
742 |
tim |
1.1 |
for (Entry e = header.next; e != header; e = e.next) |
743 |
|
|
s.writeObject(e.element); |
744 |
|
|
} |
745 |
|
|
|
746 |
|
|
/** |
747 |
|
|
* Reconstitute this <tt>LinkedList</tt> instance from a stream (that is |
748 |
|
|
* deserialize it). |
749 |
|
|
*/ |
750 |
dl |
1.3 |
private void readObject(java.io.ObjectInputStream s) |
751 |
tim |
1.1 |
throws java.io.IOException, ClassNotFoundException { |
752 |
dl |
1.3 |
// Read in any hidden serialization magic |
753 |
|
|
s.defaultReadObject(); |
754 |
tim |
1.1 |
|
755 |
|
|
// Read in size |
756 |
|
|
int size = s.readInt(); |
757 |
|
|
|
758 |
|
|
// Initialize header |
759 |
dl |
1.3 |
header = new Entry<E>(null, null, null); |
760 |
tim |
1.1 |
header.next = header.previous = header; |
761 |
|
|
|
762 |
dl |
1.3 |
// Read in all elements in the proper order. |
763 |
|
|
for (int i=0; i<size; i++) |
764 |
|
|
addBefore((E)s.readObject(), header); |
765 |
tim |
1.1 |
} |
766 |
|
|
} |