1 |
dl |
1.1 |
/* |
2 |
|
|
* Written by Josh Bloch of Google Inc. and released to the public domain, |
3 |
jsr166 |
1.8 |
* as explained at http://creativecommons.org/publicdomain/zero/1.0/. |
4 |
dl |
1.1 |
*/ |
5 |
|
|
|
6 |
|
|
package jsr166x; // XXX This belongs in java.util!!! XXX |
7 |
|
|
import java.util.*; // XXX This import goes away XXX |
8 |
|
|
import java.io.*; |
9 |
|
|
|
10 |
|
|
/** |
11 |
|
|
* Resizable-array implementation of the {@link Deque} interface. Array |
12 |
|
|
* deques have no capacity restrictions; they grow as necessary to support |
13 |
|
|
* usage. They are not thread-safe; in the absence of external |
14 |
|
|
* synchronization, they do not support concurrent access by multiple threads. |
15 |
|
|
* Null elements are prohibited. This class is likely to be faster than |
16 |
jsr166 |
1.7 |
* {@link Stack} when used as a stack, and faster than {@link LinkedList} |
17 |
dl |
1.1 |
* when used as a queue. |
18 |
|
|
* |
19 |
|
|
* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time. |
20 |
|
|
* Exceptions include {@link #remove(Object) remove}, {@link |
21 |
|
|
* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence |
22 |
|
|
* removeLastOccurrence}, {@link #contains contains }, {@link #iterator |
23 |
|
|
* iterator.remove()}, and the bulk operations, all of which run in linear |
24 |
|
|
* time. |
25 |
|
|
* |
26 |
|
|
* <p>The iterators returned by this class's <tt>iterator</tt> method are |
27 |
|
|
* <i>fail-fast</i>: If the deque is modified at any time after the iterator |
28 |
|
|
* is created, in any way except through the iterator's own remove method, the |
29 |
|
|
* iterator will generally throw a {@link ConcurrentModificationException}. |
30 |
|
|
* Thus, in the face of concurrent modification, the iterator fails quickly |
31 |
|
|
* and cleanly, rather than risking arbitrary, non-deterministic behavior at |
32 |
|
|
* an undetermined time in the future. |
33 |
|
|
* |
34 |
|
|
* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
35 |
|
|
* as it is, generally speaking, impossible to make any hard guarantees in the |
36 |
|
|
* presence of unsynchronized concurrent modification. Fail-fast iterators |
37 |
jsr166 |
1.3 |
* throw <tt>ConcurrentModificationException</tt> on a best-effort basis. |
38 |
dl |
1.1 |
* Therefore, it would be wrong to write a program that depended on this |
39 |
|
|
* exception for its correctness: <i>the fail-fast behavior of iterators |
40 |
|
|
* should be used only to detect bugs.</i> |
41 |
|
|
* |
42 |
|
|
* <p>This class and its iterator implement all of the |
43 |
|
|
* optional methods of the {@link Collection} and {@link |
44 |
|
|
* Iterator} interfaces. This class is a member of the <a |
45 |
|
|
* href="{@docRoot}/../guide/collections/index.html"> Java Collections |
46 |
|
|
* Framework</a>. |
47 |
|
|
* |
48 |
|
|
* @author Josh Bloch and Doug Lea |
49 |
|
|
* @since 1.6 |
50 |
|
|
* @param <E> the type of elements held in this collection |
51 |
|
|
*/ |
52 |
|
|
public class ArrayDeque<E> extends AbstractCollection<E> |
53 |
|
|
implements Deque<E>, Cloneable, Serializable |
54 |
|
|
{ |
55 |
|
|
/** |
56 |
|
|
* The array in which the elements of in the deque are stored. |
57 |
|
|
* The capacity of the deque is the length of this array, which is |
58 |
|
|
* always a power of two. The array is never allowed to become |
59 |
|
|
* full, except transiently within an addX method where it is |
60 |
|
|
* resized (see doubleCapacity) immediately upon becoming full, |
61 |
|
|
* thus avoiding head and tail wrapping around to equal each |
62 |
|
|
* other. We also guarantee that all array cells not holding |
63 |
|
|
* deque elements are always null. |
64 |
|
|
*/ |
65 |
|
|
private transient E[] elements; |
66 |
|
|
|
67 |
|
|
/** |
68 |
|
|
* The index of the element at the head of the deque (which is the |
69 |
|
|
* element that would be removed by remove() or pop()); or an |
70 |
|
|
* arbitrary number equal to tail if the deque is empty. |
71 |
|
|
*/ |
72 |
|
|
private transient int head; |
73 |
|
|
|
74 |
|
|
/** |
75 |
|
|
* The index at which the next element would be added to the tail |
76 |
|
|
* of the deque (via addLast(E), add(E), or push(E)). |
77 |
|
|
*/ |
78 |
|
|
private transient int tail; |
79 |
|
|
|
80 |
|
|
/** |
81 |
|
|
* The minimum capacity that we'll use for a newly created deque. |
82 |
|
|
* Must be a power of 2. |
83 |
|
|
*/ |
84 |
|
|
private static final int MIN_INITIAL_CAPACITY = 8; |
85 |
|
|
|
86 |
|
|
// ****** Array allocation and resizing utilities ****** |
87 |
|
|
|
88 |
|
|
/** |
89 |
|
|
* Allocate empty array to hold the given number of elements. |
90 |
|
|
* |
91 |
|
|
* @param numElements the number of elements to hold. |
92 |
|
|
*/ |
93 |
jsr166 |
1.3 |
private void allocateElements(int numElements) { |
94 |
dl |
1.1 |
int initialCapacity = MIN_INITIAL_CAPACITY; |
95 |
|
|
// Find the best power of two to hold elements. |
96 |
|
|
// Tests "<=" because arrays aren't kept full. |
97 |
|
|
if (numElements >= initialCapacity) { |
98 |
|
|
initialCapacity = numElements; |
99 |
|
|
initialCapacity |= (initialCapacity >>> 1); |
100 |
|
|
initialCapacity |= (initialCapacity >>> 2); |
101 |
|
|
initialCapacity |= (initialCapacity >>> 4); |
102 |
|
|
initialCapacity |= (initialCapacity >>> 8); |
103 |
|
|
initialCapacity |= (initialCapacity >>> 16); |
104 |
|
|
initialCapacity++; |
105 |
|
|
|
106 |
|
|
if (initialCapacity < 0) // Too many elements, must back off |
107 |
|
|
initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements |
108 |
|
|
} |
109 |
|
|
elements = (E[]) new Object[initialCapacity]; |
110 |
|
|
} |
111 |
|
|
|
112 |
|
|
/** |
113 |
|
|
* Double the capacity of this deque. Call only when full, i.e., |
114 |
|
|
* when head and tail have wrapped around to become equal. |
115 |
|
|
*/ |
116 |
|
|
private void doubleCapacity() { |
117 |
jsr166 |
1.3 |
assert head == tail; |
118 |
dl |
1.1 |
int p = head; |
119 |
|
|
int n = elements.length; |
120 |
|
|
int r = n - p; // number of elements to the right of p |
121 |
|
|
int newCapacity = n << 1; |
122 |
|
|
if (newCapacity < 0) |
123 |
|
|
throw new IllegalStateException("Sorry, deque too big"); |
124 |
|
|
Object[] a = new Object[newCapacity]; |
125 |
|
|
System.arraycopy(elements, p, a, 0, r); |
126 |
|
|
System.arraycopy(elements, 0, a, r, p); |
127 |
|
|
elements = (E[])a; |
128 |
|
|
head = 0; |
129 |
|
|
tail = n; |
130 |
|
|
} |
131 |
|
|
|
132 |
|
|
/** |
133 |
|
|
* Copy the elements from our element array into the specified array, |
134 |
|
|
* in order (from first to last element in the deque). It is assumed |
135 |
|
|
* that the array is large enough to hold all elements in the deque. |
136 |
|
|
* |
137 |
|
|
* @return its argument |
138 |
|
|
*/ |
139 |
|
|
private <T> T[] copyElements(T[] a) { |
140 |
|
|
if (head < tail) { |
141 |
|
|
System.arraycopy(elements, head, a, 0, size()); |
142 |
|
|
} else if (head > tail) { |
143 |
|
|
int headPortionLen = elements.length - head; |
144 |
|
|
System.arraycopy(elements, head, a, 0, headPortionLen); |
145 |
|
|
System.arraycopy(elements, 0, a, headPortionLen, tail); |
146 |
|
|
} |
147 |
|
|
return a; |
148 |
|
|
} |
149 |
|
|
|
150 |
|
|
/** |
151 |
|
|
* Constructs an empty array deque with the an initial capacity |
152 |
|
|
* sufficient to hold 16 elements. |
153 |
|
|
*/ |
154 |
|
|
public ArrayDeque() { |
155 |
|
|
elements = (E[]) new Object[16]; |
156 |
|
|
} |
157 |
|
|
|
158 |
|
|
/** |
159 |
|
|
* Constructs an empty array deque with an initial capacity |
160 |
|
|
* sufficient to hold the specified number of elements. |
161 |
|
|
* |
162 |
|
|
* @param numElements lower bound on initial capacity of the deque |
163 |
|
|
*/ |
164 |
|
|
public ArrayDeque(int numElements) { |
165 |
|
|
allocateElements(numElements); |
166 |
|
|
} |
167 |
|
|
|
168 |
|
|
/** |
169 |
|
|
* Constructs a deque containing the elements of the specified |
170 |
|
|
* collection, in the order they are returned by the collection's |
171 |
|
|
* iterator. (The first element returned by the collection's |
172 |
|
|
* iterator becomes the first element, or <i>front</i> of the |
173 |
|
|
* deque.) |
174 |
|
|
* |
175 |
|
|
* @param c the collection whose elements are to be placed into the deque |
176 |
|
|
* @throws NullPointerException if the specified collection is null |
177 |
|
|
*/ |
178 |
|
|
public ArrayDeque(Collection<? extends E> c) { |
179 |
|
|
allocateElements(c.size()); |
180 |
|
|
addAll(c); |
181 |
|
|
} |
182 |
|
|
|
183 |
|
|
// The main insertion and extraction methods are addFirst, |
184 |
|
|
// addLast, pollFirst, pollLast. The other methods are defined in |
185 |
|
|
// terms of these. |
186 |
|
|
|
187 |
|
|
/** |
188 |
|
|
* Inserts the specified element to the front this deque. |
189 |
|
|
* |
190 |
|
|
* @param e the element to insert |
191 |
|
|
* @throws NullPointerException if <tt>e</tt> is null |
192 |
|
|
*/ |
193 |
|
|
public void addFirst(E e) { |
194 |
|
|
if (e == null) |
195 |
|
|
throw new NullPointerException(); |
196 |
|
|
elements[head = (head - 1) & (elements.length - 1)] = e; |
197 |
jsr166 |
1.3 |
if (head == tail) |
198 |
dl |
1.1 |
doubleCapacity(); |
199 |
|
|
} |
200 |
|
|
|
201 |
|
|
/** |
202 |
|
|
* Inserts the specified element to the end this deque. |
203 |
|
|
* This method is equivalent to {@link Collection#add} and |
204 |
|
|
* {@link #push}. |
205 |
|
|
* |
206 |
|
|
* @param e the element to insert |
207 |
|
|
* @throws NullPointerException if <tt>e</tt> is null |
208 |
|
|
*/ |
209 |
|
|
public void addLast(E e) { |
210 |
|
|
if (e == null) |
211 |
|
|
throw new NullPointerException(); |
212 |
|
|
elements[tail] = e; |
213 |
|
|
if ( (tail = (tail + 1) & (elements.length - 1)) == head) |
214 |
|
|
doubleCapacity(); |
215 |
|
|
} |
216 |
|
|
|
217 |
|
|
/** |
218 |
|
|
* Retrieves and removes the first element of this deque, or |
219 |
|
|
* <tt>null</tt> if this deque is empty. |
220 |
|
|
* |
221 |
|
|
* @return the first element of this deque, or <tt>null</tt> if |
222 |
|
|
* this deque is empty |
223 |
|
|
*/ |
224 |
|
|
public E pollFirst() { |
225 |
|
|
int h = head; |
226 |
|
|
E result = elements[h]; // Element is null if deque empty |
227 |
|
|
if (result == null) |
228 |
|
|
return null; |
229 |
|
|
elements[h] = null; // Must null out slot |
230 |
|
|
head = (h + 1) & (elements.length - 1); |
231 |
|
|
return result; |
232 |
|
|
} |
233 |
|
|
|
234 |
|
|
/** |
235 |
|
|
* Retrieves and removes the last element of this deque, or |
236 |
|
|
* <tt>null</tt> if this deque is empty. |
237 |
|
|
* |
238 |
|
|
* @return the last element of this deque, or <tt>null</tt> if |
239 |
|
|
* this deque is empty |
240 |
|
|
*/ |
241 |
|
|
public E pollLast() { |
242 |
|
|
int t = (tail - 1) & (elements.length - 1); |
243 |
|
|
E result = elements[t]; |
244 |
|
|
if (result == null) |
245 |
|
|
return null; |
246 |
jsr166 |
1.3 |
elements[t] = null; |
247 |
dl |
1.1 |
tail = t; |
248 |
|
|
return result; |
249 |
|
|
} |
250 |
|
|
|
251 |
|
|
/** |
252 |
|
|
* Inserts the specified element to the front this deque. |
253 |
|
|
* |
254 |
|
|
* @param e the element to insert |
255 |
|
|
* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst}) |
256 |
|
|
* @throws NullPointerException if <tt>e</tt> is null |
257 |
|
|
*/ |
258 |
|
|
public boolean offerFirst(E e) { |
259 |
|
|
addFirst(e); |
260 |
|
|
return true; |
261 |
|
|
} |
262 |
|
|
|
263 |
|
|
/** |
264 |
|
|
* Inserts the specified element to the end this deque. |
265 |
|
|
* |
266 |
|
|
* @param e the element to insert |
267 |
|
|
* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast}) |
268 |
|
|
* @throws NullPointerException if <tt>e</tt> is null |
269 |
|
|
*/ |
270 |
|
|
public boolean offerLast(E e) { |
271 |
|
|
addLast(e); |
272 |
|
|
return true; |
273 |
|
|
} |
274 |
|
|
|
275 |
|
|
/** |
276 |
|
|
* Retrieves and removes the first element of this deque. This method |
277 |
|
|
* differs from the <tt>pollFirst</tt> method in that it throws an |
278 |
|
|
* exception if this deque is empty. |
279 |
|
|
* |
280 |
|
|
* @return the first element of this deque |
281 |
|
|
* @throws NoSuchElementException if this deque is empty |
282 |
|
|
*/ |
283 |
|
|
public E removeFirst() { |
284 |
|
|
E x = pollFirst(); |
285 |
|
|
if (x == null) |
286 |
|
|
throw new NoSuchElementException(); |
287 |
|
|
return x; |
288 |
|
|
} |
289 |
|
|
|
290 |
|
|
/** |
291 |
|
|
* Retrieves and removes the last element of this deque. This method |
292 |
|
|
* differs from the <tt>pollLast</tt> method in that it throws an |
293 |
|
|
* exception if this deque is empty. |
294 |
|
|
* |
295 |
|
|
* @return the last element of this deque |
296 |
|
|
* @throws NoSuchElementException if this deque is empty |
297 |
|
|
*/ |
298 |
|
|
public E removeLast() { |
299 |
|
|
E x = pollLast(); |
300 |
|
|
if (x == null) |
301 |
|
|
throw new NoSuchElementException(); |
302 |
|
|
return x; |
303 |
|
|
} |
304 |
|
|
|
305 |
|
|
/** |
306 |
|
|
* Retrieves, but does not remove, the first element of this deque, |
307 |
|
|
* returning <tt>null</tt> if this deque is empty. |
308 |
|
|
* |
309 |
|
|
* @return the first element of this deque, or <tt>null</tt> if |
310 |
|
|
* this deque is empty |
311 |
|
|
*/ |
312 |
|
|
public E peekFirst() { |
313 |
|
|
return elements[head]; // elements[head] is null if deque empty |
314 |
|
|
} |
315 |
|
|
|
316 |
|
|
/** |
317 |
|
|
* Retrieves, but does not remove, the last element of this deque, |
318 |
|
|
* returning <tt>null</tt> if this deque is empty. |
319 |
|
|
* |
320 |
|
|
* @return the last element of this deque, or <tt>null</tt> if this deque |
321 |
|
|
* is empty |
322 |
|
|
*/ |
323 |
|
|
public E peekLast() { |
324 |
|
|
return elements[(tail - 1) & (elements.length - 1)]; |
325 |
|
|
} |
326 |
|
|
|
327 |
|
|
/** |
328 |
|
|
* Retrieves, but does not remove, the first element of this |
329 |
|
|
* deque. This method differs from the <tt>peek</tt> method only |
330 |
|
|
* in that it throws an exception if this deque is empty. |
331 |
|
|
* |
332 |
|
|
* @return the first element of this deque |
333 |
|
|
* @throws NoSuchElementException if this deque is empty |
334 |
|
|
*/ |
335 |
dl |
1.2 |
public E getFirst() { |
336 |
dl |
1.1 |
E x = elements[head]; |
337 |
|
|
if (x == null) |
338 |
|
|
throw new NoSuchElementException(); |
339 |
|
|
return x; |
340 |
|
|
} |
341 |
|
|
|
342 |
|
|
/** |
343 |
|
|
* Retrieves, but does not remove, the last element of this |
344 |
|
|
* deque. This method differs from the <tt>peek</tt> method only |
345 |
|
|
* in that it throws an exception if this deque is empty. |
346 |
|
|
* |
347 |
|
|
* @return the last element of this deque |
348 |
|
|
* @throws NoSuchElementException if this deque is empty |
349 |
|
|
*/ |
350 |
dl |
1.2 |
public E getLast() { |
351 |
dl |
1.1 |
E x = elements[(tail - 1) & (elements.length - 1)]; |
352 |
|
|
if (x == null) |
353 |
|
|
throw new NoSuchElementException(); |
354 |
|
|
return x; |
355 |
|
|
} |
356 |
|
|
|
357 |
|
|
/** |
358 |
|
|
* Removes the first occurrence of the specified element in this |
359 |
|
|
* deque (when traversing the deque from head to tail). If the deque |
360 |
|
|
* does not contain the element, it is unchanged. |
361 |
|
|
* |
362 |
|
|
* @param e element to be removed from this deque, if present |
363 |
|
|
* @return <tt>true</tt> if the deque contained the specified element |
364 |
|
|
*/ |
365 |
|
|
public boolean removeFirstOccurrence(Object e) { |
366 |
|
|
if (e == null) |
367 |
|
|
return false; |
368 |
|
|
int mask = elements.length - 1; |
369 |
|
|
int i = head; |
370 |
|
|
E x; |
371 |
|
|
while ( (x = elements[i]) != null) { |
372 |
|
|
if (e.equals(x)) { |
373 |
|
|
delete(i); |
374 |
|
|
return true; |
375 |
|
|
} |
376 |
|
|
i = (i + 1) & mask; |
377 |
|
|
} |
378 |
|
|
return false; |
379 |
|
|
} |
380 |
|
|
|
381 |
|
|
/** |
382 |
|
|
* Removes the last occurrence of the specified element in this |
383 |
|
|
* deque (when traversing the deque from head to tail). If the deque |
384 |
|
|
* does not contain the element, it is unchanged. |
385 |
|
|
* |
386 |
|
|
* @param e element to be removed from this deque, if present |
387 |
|
|
* @return <tt>true</tt> if the deque contained the specified element |
388 |
|
|
*/ |
389 |
|
|
public boolean removeLastOccurrence(Object e) { |
390 |
|
|
if (e == null) |
391 |
|
|
return false; |
392 |
|
|
int mask = elements.length - 1; |
393 |
|
|
int i = (tail - 1) & mask; |
394 |
|
|
E x; |
395 |
|
|
while ( (x = elements[i]) != null) { |
396 |
|
|
if (e.equals(x)) { |
397 |
|
|
delete(i); |
398 |
|
|
return true; |
399 |
|
|
} |
400 |
|
|
i = (i - 1) & mask; |
401 |
|
|
} |
402 |
|
|
return false; |
403 |
|
|
} |
404 |
|
|
|
405 |
|
|
// *** Queue methods *** |
406 |
|
|
|
407 |
|
|
/** |
408 |
|
|
* Inserts the specified element to the end of this deque. |
409 |
|
|
* |
410 |
|
|
* <p>This method is equivalent to {@link #offerLast}. |
411 |
|
|
* |
412 |
|
|
* @param e the element to insert |
413 |
|
|
* @return <tt>true</tt> (as per the spec for {@link Queue#offer}) |
414 |
|
|
* @throws NullPointerException if <tt>e</tt> is null |
415 |
|
|
*/ |
416 |
|
|
public boolean offer(E e) { |
417 |
|
|
return offerLast(e); |
418 |
|
|
} |
419 |
|
|
|
420 |
|
|
/** |
421 |
|
|
* Inserts the specified element to the end of this deque. |
422 |
|
|
* |
423 |
|
|
* <p>This method is equivalent to {@link #addLast}. |
424 |
|
|
* |
425 |
|
|
* @param e the element to insert |
426 |
|
|
* @return <tt>true</tt> (as per the spec for {@link Collection#add}) |
427 |
|
|
* @throws NullPointerException if <tt>e</tt> is null |
428 |
|
|
*/ |
429 |
|
|
public boolean add(E e) { |
430 |
|
|
addLast(e); |
431 |
|
|
return true; |
432 |
|
|
} |
433 |
|
|
|
434 |
|
|
/** |
435 |
|
|
* Retrieves and removes the head of the queue represented by |
436 |
|
|
* this deque, or <tt>null</tt> if this deque is empty. In other words, |
437 |
|
|
* retrieves and removes the first element of this deque, or <tt>null</tt> |
438 |
|
|
* if this deque is empty. |
439 |
|
|
* |
440 |
|
|
* <p>This method is equivalent to {@link #pollFirst}. |
441 |
|
|
* |
442 |
|
|
* @return the first element of this deque, or <tt>null</tt> if |
443 |
|
|
* this deque is empty |
444 |
|
|
*/ |
445 |
|
|
public E poll() { |
446 |
|
|
return pollFirst(); |
447 |
|
|
} |
448 |
|
|
|
449 |
|
|
/** |
450 |
|
|
* Retrieves and removes the head of the queue represented by this deque. |
451 |
|
|
* This method differs from the <tt>poll</tt> method in that it throws an |
452 |
|
|
* exception if this deque is empty. |
453 |
|
|
* |
454 |
|
|
* <p>This method is equivalent to {@link #removeFirst}. |
455 |
|
|
* |
456 |
|
|
* @return the head of the queue represented by this deque |
457 |
|
|
* @throws NoSuchElementException if this deque is empty |
458 |
|
|
*/ |
459 |
|
|
public E remove() { |
460 |
|
|
return removeFirst(); |
461 |
|
|
} |
462 |
|
|
|
463 |
|
|
/** |
464 |
|
|
* Retrieves, but does not remove, the head of the queue represented by |
465 |
|
|
* this deque, returning <tt>null</tt> if this deque is empty. |
466 |
|
|
* |
467 |
|
|
* <p>This method is equivalent to {@link #peekFirst} |
468 |
|
|
* |
469 |
|
|
* @return the head of the queue represented by this deque, or |
470 |
|
|
* <tt>null</tt> if this deque is empty |
471 |
|
|
*/ |
472 |
|
|
public E peek() { |
473 |
|
|
return peekFirst(); |
474 |
|
|
} |
475 |
|
|
|
476 |
|
|
/** |
477 |
|
|
* Retrieves, but does not remove, the head of the queue represented by |
478 |
|
|
* this deque. This method differs from the <tt>peek</tt> method only in |
479 |
|
|
* that it throws an exception if this deque is empty. |
480 |
|
|
* |
481 |
dl |
1.2 |
* <p>This method is equivalent to {@link #getFirst} |
482 |
dl |
1.1 |
* |
483 |
|
|
* @return the head of the queue represented by this deque |
484 |
|
|
* @throws NoSuchElementException if this deque is empty |
485 |
|
|
*/ |
486 |
|
|
public E element() { |
487 |
dl |
1.2 |
return getFirst(); |
488 |
dl |
1.1 |
} |
489 |
|
|
|
490 |
|
|
// *** Stack methods *** |
491 |
|
|
|
492 |
|
|
/** |
493 |
|
|
* Pushes an element onto the stack represented by this deque. In other |
494 |
|
|
* words, inserts the element to the front this deque. |
495 |
|
|
* |
496 |
|
|
* <p>This method is equivalent to {@link #addFirst}. |
497 |
|
|
* |
498 |
|
|
* @param e the element to push |
499 |
|
|
* @throws NullPointerException if <tt>e</tt> is null |
500 |
|
|
*/ |
501 |
|
|
public void push(E e) { |
502 |
|
|
addFirst(e); |
503 |
|
|
} |
504 |
|
|
|
505 |
|
|
/** |
506 |
|
|
* Pops an element from the stack represented by this deque. In other |
507 |
jsr166 |
1.5 |
* words, removes and returns the first element of this deque. |
508 |
dl |
1.1 |
* |
509 |
|
|
* <p>This method is equivalent to {@link #removeFirst()}. |
510 |
|
|
* |
511 |
|
|
* @return the element at the front of this deque (which is the top |
512 |
|
|
* of the stack represented by this deque) |
513 |
|
|
* @throws NoSuchElementException if this deque is empty |
514 |
|
|
*/ |
515 |
|
|
public E pop() { |
516 |
|
|
return removeFirst(); |
517 |
|
|
} |
518 |
|
|
|
519 |
|
|
/** |
520 |
|
|
* Remove the element at the specified position in the elements array, |
521 |
|
|
* adjusting head, tail, and size as necessary. This can result in |
522 |
|
|
* motion of elements backwards or forwards in the array. |
523 |
|
|
* |
524 |
|
|
* <p>This method is called delete rather than remove to emphasize the |
525 |
|
|
* that that its semantics differ from those of List.remove(int). |
526 |
jsr166 |
1.3 |
* |
527 |
dl |
1.1 |
* @return true if elements moved backwards |
528 |
|
|
*/ |
529 |
|
|
private boolean delete(int i) { |
530 |
|
|
// Case 1: Deque doesn't wrap |
531 |
|
|
// Case 2: Deque does wrap and removed element is in the head portion |
532 |
|
|
if ((head < tail || tail == 0) || i >= head) { |
533 |
|
|
System.arraycopy(elements, head, elements, head + 1, i - head); |
534 |
|
|
elements[head] = null; |
535 |
|
|
head = (head + 1) & (elements.length - 1); |
536 |
|
|
return false; |
537 |
|
|
} |
538 |
|
|
|
539 |
|
|
// Case 3: Deque wraps and removed element is in the tail portion |
540 |
|
|
tail--; |
541 |
|
|
System.arraycopy(elements, i + 1, elements, i, tail - i); |
542 |
|
|
elements[tail] = null; |
543 |
|
|
return true; |
544 |
|
|
} |
545 |
|
|
|
546 |
|
|
// *** Collection Methods *** |
547 |
|
|
|
548 |
|
|
/** |
549 |
|
|
* Returns the number of elements in this deque. |
550 |
|
|
* |
551 |
|
|
* @return the number of elements in this deque |
552 |
|
|
*/ |
553 |
|
|
public int size() { |
554 |
|
|
return (tail - head) & (elements.length - 1); |
555 |
|
|
} |
556 |
|
|
|
557 |
|
|
/** |
558 |
|
|
* Returns <tt>true</tt> if this collection contains no elements.<p> |
559 |
|
|
* |
560 |
|
|
* @return <tt>true</tt> if this collection contains no elements. |
561 |
|
|
*/ |
562 |
|
|
public boolean isEmpty() { |
563 |
|
|
return head == tail; |
564 |
|
|
} |
565 |
|
|
|
566 |
|
|
/** |
567 |
|
|
* Returns an iterator over the elements in this deque. The elements |
568 |
|
|
* will be ordered from first (head) to last (tail). This is the same |
569 |
|
|
* order that elements would be dequeued (via successive calls to |
570 |
|
|
* {@link #remove} or popped (via successive calls to {@link #pop}). |
571 |
jsr166 |
1.3 |
* |
572 |
dl |
1.1 |
* @return an <tt>Iterator</tt> over the elements in this deque |
573 |
|
|
*/ |
574 |
|
|
public Iterator<E> iterator() { |
575 |
|
|
return new DeqIterator(); |
576 |
|
|
} |
577 |
|
|
|
578 |
|
|
private class DeqIterator implements Iterator<E> { |
579 |
|
|
/** |
580 |
|
|
* Index of element to be returned by subsequent call to next. |
581 |
|
|
*/ |
582 |
|
|
private int cursor = head; |
583 |
|
|
|
584 |
|
|
/** |
585 |
|
|
* Tail recorded at construction (also in remove), to stop |
586 |
|
|
* iterator and also to check for comodification. |
587 |
|
|
*/ |
588 |
|
|
private int fence = tail; |
589 |
|
|
|
590 |
|
|
/** |
591 |
|
|
* Index of element returned by most recent call to next. |
592 |
|
|
* Reset to -1 if element is deleted by a call to remove. |
593 |
|
|
*/ |
594 |
|
|
private int lastRet = -1; |
595 |
|
|
|
596 |
|
|
public boolean hasNext() { |
597 |
|
|
return cursor != fence; |
598 |
|
|
} |
599 |
|
|
|
600 |
|
|
public E next() { |
601 |
|
|
E result; |
602 |
|
|
if (cursor == fence) |
603 |
|
|
throw new NoSuchElementException(); |
604 |
|
|
// This check doesn't catch all possible comodifications, |
605 |
|
|
// but does catch the ones that corrupt traversal |
606 |
|
|
if (tail != fence || (result = elements[cursor]) == null) |
607 |
|
|
throw new ConcurrentModificationException(); |
608 |
|
|
lastRet = cursor; |
609 |
|
|
cursor = (cursor + 1) & (elements.length - 1); |
610 |
|
|
return result; |
611 |
|
|
} |
612 |
|
|
|
613 |
|
|
public void remove() { |
614 |
|
|
if (lastRet < 0) |
615 |
|
|
throw new IllegalStateException(); |
616 |
|
|
if (delete(lastRet)) |
617 |
|
|
cursor--; |
618 |
|
|
lastRet = -1; |
619 |
|
|
fence = tail; |
620 |
|
|
} |
621 |
|
|
} |
622 |
|
|
|
623 |
|
|
/** |
624 |
|
|
* Returns <tt>true</tt> if this deque contains the specified |
625 |
|
|
* element. More formally, returns <tt>true</tt> if and only if this |
626 |
|
|
* deque contains at least one element <tt>e</tt> such that |
627 |
|
|
* <tt>e.equals(o)</tt>. |
628 |
|
|
* |
629 |
|
|
* @param o object to be checked for containment in this deque |
630 |
|
|
* @return <tt>true</tt> if this deque contains the specified element |
631 |
|
|
*/ |
632 |
|
|
public boolean contains(Object o) { |
633 |
|
|
if (o == null) |
634 |
|
|
return false; |
635 |
|
|
int mask = elements.length - 1; |
636 |
|
|
int i = head; |
637 |
|
|
E x; |
638 |
|
|
while ( (x = elements[i]) != null) { |
639 |
|
|
if (o.equals(x)) |
640 |
|
|
return true; |
641 |
|
|
i = (i + 1) & mask; |
642 |
|
|
} |
643 |
|
|
return false; |
644 |
|
|
} |
645 |
|
|
|
646 |
|
|
/** |
647 |
|
|
* Removes a single instance of the specified element from this deque. |
648 |
|
|
* This method is equivalent to {@link #removeFirstOccurrence}. |
649 |
|
|
* |
650 |
|
|
* @param e element to be removed from this deque, if present |
651 |
|
|
* @return <tt>true</tt> if this deque contained the specified element |
652 |
|
|
*/ |
653 |
|
|
public boolean remove(Object e) { |
654 |
|
|
return removeFirstOccurrence(e); |
655 |
|
|
} |
656 |
|
|
|
657 |
|
|
/** |
658 |
|
|
* Removes all of the elements from this deque. |
659 |
|
|
*/ |
660 |
|
|
public void clear() { |
661 |
|
|
int h = head; |
662 |
|
|
int t = tail; |
663 |
|
|
if (h != t) { // clear all cells |
664 |
|
|
head = tail = 0; |
665 |
|
|
int i = h; |
666 |
|
|
int mask = elements.length - 1; |
667 |
|
|
do { |
668 |
|
|
elements[i] = null; |
669 |
|
|
i = (i + 1) & mask; |
670 |
jsr166 |
1.6 |
} while (i != t); |
671 |
dl |
1.1 |
} |
672 |
|
|
} |
673 |
|
|
|
674 |
|
|
/** |
675 |
|
|
* Returns an array containing all of the elements in this list |
676 |
|
|
* in the correct order. |
677 |
|
|
* |
678 |
|
|
* @return an array containing all of the elements in this list |
679 |
jsr166 |
1.4 |
* in the correct order |
680 |
dl |
1.1 |
*/ |
681 |
|
|
public Object[] toArray() { |
682 |
jsr166 |
1.4 |
return copyElements(new Object[size()]); |
683 |
dl |
1.1 |
} |
684 |
|
|
|
685 |
|
|
/** |
686 |
|
|
* Returns an array containing all of the elements in this deque in the |
687 |
|
|
* correct order; the runtime type of the returned array is that of the |
688 |
|
|
* specified array. If the deque fits in the specified array, it is |
689 |
|
|
* returned therein. Otherwise, a new array is allocated with the runtime |
690 |
|
|
* type of the specified array and the size of this deque. |
691 |
|
|
* |
692 |
|
|
* <p>If the deque fits in the specified array with room to spare (i.e., |
693 |
|
|
* the array has more elements than the deque), the element in the array |
694 |
|
|
* immediately following the end of the collection is set to <tt>null</tt>. |
695 |
|
|
* |
696 |
|
|
* @param a the array into which the elements of the deque are to |
697 |
jsr166 |
1.4 |
* be stored, if it is big enough; otherwise, a new array of the |
698 |
|
|
* same runtime type is allocated for this purpose |
699 |
dl |
1.1 |
* @return an array containing the elements of the deque |
700 |
|
|
* @throws ArrayStoreException if the runtime type of a is not a supertype |
701 |
|
|
* of the runtime type of every element in this deque |
702 |
|
|
*/ |
703 |
|
|
public <T> T[] toArray(T[] a) { |
704 |
|
|
int size = size(); |
705 |
|
|
if (a.length < size) |
706 |
|
|
a = (T[])java.lang.reflect.Array.newInstance( |
707 |
|
|
a.getClass().getComponentType(), size); |
708 |
jsr166 |
1.4 |
copyElements(a); |
709 |
dl |
1.1 |
if (a.length > size) |
710 |
|
|
a[size] = null; |
711 |
|
|
return a; |
712 |
|
|
} |
713 |
|
|
|
714 |
|
|
// *** Object methods *** |
715 |
|
|
|
716 |
|
|
/** |
717 |
|
|
* Returns a copy of this deque. |
718 |
|
|
* |
719 |
|
|
* @return a copy of this deque |
720 |
|
|
*/ |
721 |
|
|
public ArrayDeque<E> clone() { |
722 |
jsr166 |
1.3 |
try { |
723 |
dl |
1.1 |
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
724 |
|
|
// These two lines are currently faster than cloning the array: |
725 |
|
|
result.elements = (E[]) new Object[elements.length]; |
726 |
|
|
System.arraycopy(elements, 0, result.elements, 0, elements.length); |
727 |
|
|
return result; |
728 |
|
|
|
729 |
jsr166 |
1.3 |
} catch (CloneNotSupportedException e) { |
730 |
dl |
1.1 |
throw new AssertionError(); |
731 |
|
|
} |
732 |
|
|
} |
733 |
|
|
|
734 |
|
|
/** |
735 |
|
|
* Appease the serialization gods. |
736 |
|
|
*/ |
737 |
|
|
private static final long serialVersionUID = 2340985798034038923L; |
738 |
|
|
|
739 |
|
|
/** |
740 |
|
|
* Serialize this deque. |
741 |
|
|
* |
742 |
|
|
* @serialData The current size (<tt>int</tt>) of the deque, |
743 |
|
|
* followed by all of its elements (each an object reference) in |
744 |
|
|
* first-to-last order. |
745 |
|
|
*/ |
746 |
|
|
private void writeObject(ObjectOutputStream s) throws IOException { |
747 |
|
|
s.defaultWriteObject(); |
748 |
|
|
|
749 |
|
|
// Write out size |
750 |
|
|
int size = size(); |
751 |
|
|
s.writeInt(size); |
752 |
|
|
|
753 |
|
|
// Write out elements in order. |
754 |
|
|
int i = head; |
755 |
|
|
int mask = elements.length - 1; |
756 |
|
|
for (int j = 0; j < size; j++) { |
757 |
|
|
s.writeObject(elements[i]); |
758 |
|
|
i = (i + 1) & mask; |
759 |
|
|
} |
760 |
|
|
} |
761 |
|
|
|
762 |
|
|
/** |
763 |
|
|
* Deserialize this deque. |
764 |
|
|
*/ |
765 |
|
|
private void readObject(ObjectInputStream s) |
766 |
|
|
throws IOException, ClassNotFoundException { |
767 |
|
|
s.defaultReadObject(); |
768 |
|
|
|
769 |
|
|
// Read in size and allocate array |
770 |
|
|
int size = s.readInt(); |
771 |
|
|
allocateElements(size); |
772 |
|
|
head = 0; |
773 |
|
|
tail = size; |
774 |
|
|
|
775 |
|
|
// Read in all elements in the proper order. |
776 |
|
|
for (int i = 0; i < size; i++) |
777 |
|
|
elements[i] = (E)s.readObject(); |
778 |
|
|
|
779 |
|
|
} |
780 |
|
|
} |