1 |
dl |
1.2 |
/* |
2 |
|
|
* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
dl |
1.38 |
* Expert Group and released to the public domain, as explained at |
4 |
jsr166 |
1.78 |
* http://creativecommons.org/publicdomain/zero/1.0/ |
5 |
dl |
1.2 |
*/ |
6 |
|
|
|
7 |
tim |
1.1 |
package java.util.concurrent; |
8 |
dl |
1.11 |
import java.util.concurrent.locks.*; |
9 |
tim |
1.1 |
import java.util.*; |
10 |
|
|
|
11 |
|
|
/** |
12 |
dl |
1.25 |
* A bounded {@linkplain BlockingQueue blocking queue} backed by an |
13 |
|
|
* array. This queue orders elements FIFO (first-in-first-out). The |
14 |
|
|
* <em>head</em> of the queue is that element that has been on the |
15 |
|
|
* queue the longest time. The <em>tail</em> of the queue is that |
16 |
|
|
* element that has been on the queue the shortest time. New elements |
17 |
|
|
* are inserted at the tail of the queue, and the queue retrieval |
18 |
|
|
* operations obtain elements at the head of the queue. |
19 |
dholmes |
1.13 |
* |
20 |
dl |
1.40 |
* <p>This is a classic "bounded buffer", in which a |
21 |
|
|
* fixed-sized array holds elements inserted by producers and |
22 |
|
|
* extracted by consumers. Once created, the capacity cannot be |
23 |
jsr166 |
1.69 |
* changed. Attempts to {@code put} an element into a full queue |
24 |
|
|
* will result in the operation blocking; attempts to {@code take} an |
25 |
dl |
1.40 |
* element from an empty queue will similarly block. |
26 |
dl |
1.11 |
* |
27 |
jsr166 |
1.72 |
* <p>This class supports an optional fairness policy for ordering |
28 |
dl |
1.42 |
* waiting producer and consumer threads. By default, this ordering |
29 |
|
|
* is not guaranteed. However, a queue constructed with fairness set |
30 |
jsr166 |
1.69 |
* to {@code true} grants threads access in FIFO order. Fairness |
31 |
dl |
1.42 |
* generally decreases throughput but reduces variability and avoids |
32 |
|
|
* starvation. |
33 |
brian |
1.7 |
* |
34 |
dl |
1.43 |
* <p>This class and its iterator implement all of the |
35 |
|
|
* <em>optional</em> methods of the {@link Collection} and {@link |
36 |
jsr166 |
1.47 |
* Iterator} interfaces. |
37 |
dl |
1.26 |
* |
38 |
dl |
1.41 |
* <p>This class is a member of the |
39 |
jsr166 |
1.54 |
* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
40 |
dl |
1.41 |
* Java Collections Framework</a>. |
41 |
|
|
* |
42 |
dl |
1.8 |
* @since 1.5 |
43 |
|
|
* @author Doug Lea |
44 |
dl |
1.33 |
* @param <E> the type of elements held in this collection |
45 |
dl |
1.8 |
*/ |
46 |
dl |
1.5 |
public class ArrayBlockingQueue<E> extends AbstractQueue<E> |
47 |
tim |
1.1 |
implements BlockingQueue<E>, java.io.Serializable { |
48 |
|
|
|
49 |
dl |
1.36 |
/** |
50 |
dl |
1.42 |
* Serialization ID. This class relies on default serialization |
51 |
|
|
* even for the items array, which is default-serialized, even if |
52 |
|
|
* it is empty. Otherwise it could not be declared final, which is |
53 |
dl |
1.36 |
* necessary here. |
54 |
|
|
*/ |
55 |
|
|
private static final long serialVersionUID = -817911632652898426L; |
56 |
|
|
|
57 |
jsr166 |
1.73 |
/** The queued items */ |
58 |
jsr166 |
1.68 |
final Object[] items; |
59 |
jsr166 |
1.73 |
|
60 |
|
|
/** items index for next take, poll, peek or remove */ |
61 |
jsr166 |
1.58 |
int takeIndex; |
62 |
jsr166 |
1.73 |
|
63 |
|
|
/** items index for next put, offer, or add */ |
64 |
jsr166 |
1.58 |
int putIndex; |
65 |
jsr166 |
1.73 |
|
66 |
|
|
/** Number of elements in the queue */ |
67 |
jsr166 |
1.59 |
int count; |
68 |
tim |
1.12 |
|
69 |
dl |
1.5 |
/* |
70 |
dl |
1.36 |
* Concurrency control uses the classic two-condition algorithm |
71 |
dl |
1.5 |
* found in any textbook. |
72 |
|
|
*/ |
73 |
|
|
|
74 |
dl |
1.11 |
/** Main lock guarding all access */ |
75 |
jsr166 |
1.58 |
final ReentrantLock lock; |
76 |
dholmes |
1.13 |
/** Condition for waiting takes */ |
77 |
dl |
1.37 |
private final Condition notEmpty; |
78 |
dl |
1.35 |
/** Condition for waiting puts */ |
79 |
dl |
1.37 |
private final Condition notFull; |
80 |
dl |
1.5 |
|
81 |
|
|
// Internal helper methods |
82 |
|
|
|
83 |
|
|
/** |
84 |
|
|
* Circularly increment i. |
85 |
|
|
*/ |
86 |
dl |
1.40 |
final int inc(int i) { |
87 |
jsr166 |
1.58 |
return (++i == items.length) ? 0 : i; |
88 |
dl |
1.5 |
} |
89 |
|
|
|
90 |
jsr166 |
1.71 |
/** |
91 |
|
|
* Circularly decrement i. |
92 |
|
|
*/ |
93 |
|
|
final int dec(int i) { |
94 |
|
|
return ((i == 0) ? items.length : i) - 1; |
95 |
|
|
} |
96 |
|
|
|
97 |
jsr166 |
1.68 |
@SuppressWarnings("unchecked") |
98 |
|
|
static <E> E cast(Object item) { |
99 |
|
|
return (E) item; |
100 |
|
|
} |
101 |
|
|
|
102 |
|
|
/** |
103 |
|
|
* Returns item at index i. |
104 |
|
|
*/ |
105 |
|
|
final E itemAt(int i) { |
106 |
jsr166 |
1.70 |
return this.<E>cast(items[i]); |
107 |
jsr166 |
1.68 |
} |
108 |
|
|
|
109 |
|
|
/** |
110 |
|
|
* Throws NullPointerException if argument is null. |
111 |
|
|
* |
112 |
|
|
* @param v the element |
113 |
|
|
*/ |
114 |
|
|
private static void checkNotNull(Object v) { |
115 |
|
|
if (v == null) |
116 |
|
|
throw new NullPointerException(); |
117 |
|
|
} |
118 |
|
|
|
119 |
dl |
1.5 |
/** |
120 |
jsr166 |
1.47 |
* Inserts element at current put position, advances, and signals. |
121 |
dl |
1.9 |
* Call only when holding lock. |
122 |
dl |
1.5 |
*/ |
123 |
|
|
private void insert(E x) { |
124 |
|
|
items[putIndex] = x; |
125 |
|
|
putIndex = inc(putIndex); |
126 |
|
|
++count; |
127 |
dl |
1.9 |
notEmpty.signal(); |
128 |
tim |
1.1 |
} |
129 |
tim |
1.12 |
|
130 |
dl |
1.5 |
/** |
131 |
jsr166 |
1.47 |
* Extracts element at current take position, advances, and signals. |
132 |
dl |
1.9 |
* Call only when holding lock. |
133 |
dl |
1.5 |
*/ |
134 |
dholmes |
1.13 |
private E extract() { |
135 |
jsr166 |
1.68 |
final Object[] items = this.items; |
136 |
jsr166 |
1.70 |
E x = this.<E>cast(items[takeIndex]); |
137 |
dl |
1.5 |
items[takeIndex] = null; |
138 |
|
|
takeIndex = inc(takeIndex); |
139 |
|
|
--count; |
140 |
dl |
1.9 |
notFull.signal(); |
141 |
dl |
1.5 |
return x; |
142 |
|
|
} |
143 |
|
|
|
144 |
|
|
/** |
145 |
jsr166 |
1.68 |
* Deletes item at position i. |
146 |
|
|
* Utility for remove and iterator.remove. |
147 |
dl |
1.9 |
* Call only when holding lock. |
148 |
dl |
1.5 |
*/ |
149 |
|
|
void removeAt(int i) { |
150 |
jsr166 |
1.68 |
final Object[] items = this.items; |
151 |
dl |
1.9 |
// if removing front item, just advance |
152 |
|
|
if (i == takeIndex) { |
153 |
|
|
items[takeIndex] = null; |
154 |
|
|
takeIndex = inc(takeIndex); |
155 |
tim |
1.23 |
} else { |
156 |
dl |
1.9 |
// slide over all others up through putIndex. |
157 |
|
|
for (;;) { |
158 |
|
|
int nexti = inc(i); |
159 |
|
|
if (nexti != putIndex) { |
160 |
|
|
items[i] = items[nexti]; |
161 |
|
|
i = nexti; |
162 |
tim |
1.23 |
} else { |
163 |
dl |
1.9 |
items[i] = null; |
164 |
|
|
putIndex = i; |
165 |
|
|
break; |
166 |
|
|
} |
167 |
dl |
1.5 |
} |
168 |
|
|
} |
169 |
dl |
1.9 |
--count; |
170 |
|
|
notFull.signal(); |
171 |
tim |
1.1 |
} |
172 |
|
|
|
173 |
|
|
/** |
174 |
jsr166 |
1.69 |
* Creates an {@code ArrayBlockingQueue} with the given (fixed) |
175 |
dholmes |
1.13 |
* capacity and default access policy. |
176 |
jsr166 |
1.50 |
* |
177 |
dholmes |
1.13 |
* @param capacity the capacity of this queue |
178 |
jsr166 |
1.69 |
* @throws IllegalArgumentException if {@code capacity < 1} |
179 |
dl |
1.5 |
*/ |
180 |
dholmes |
1.13 |
public ArrayBlockingQueue(int capacity) { |
181 |
dl |
1.36 |
this(capacity, false); |
182 |
dl |
1.5 |
} |
183 |
dl |
1.2 |
|
184 |
dl |
1.5 |
/** |
185 |
jsr166 |
1.69 |
* Creates an {@code ArrayBlockingQueue} with the given (fixed) |
186 |
dholmes |
1.13 |
* capacity and the specified access policy. |
187 |
jsr166 |
1.50 |
* |
188 |
dholmes |
1.13 |
* @param capacity the capacity of this queue |
189 |
jsr166 |
1.69 |
* @param fair if {@code true} then queue accesses for threads blocked |
190 |
jsr166 |
1.50 |
* on insertion or removal, are processed in FIFO order; |
191 |
jsr166 |
1.69 |
* if {@code false} the access order is unspecified. |
192 |
|
|
* @throws IllegalArgumentException if {@code capacity < 1} |
193 |
dl |
1.11 |
*/ |
194 |
dholmes |
1.13 |
public ArrayBlockingQueue(int capacity, boolean fair) { |
195 |
dl |
1.36 |
if (capacity <= 0) |
196 |
|
|
throw new IllegalArgumentException(); |
197 |
jsr166 |
1.68 |
this.items = new Object[capacity]; |
198 |
dl |
1.36 |
lock = new ReentrantLock(fair); |
199 |
|
|
notEmpty = lock.newCondition(); |
200 |
|
|
notFull = lock.newCondition(); |
201 |
dl |
1.5 |
} |
202 |
|
|
|
203 |
dholmes |
1.16 |
/** |
204 |
jsr166 |
1.69 |
* Creates an {@code ArrayBlockingQueue} with the given (fixed) |
205 |
dholmes |
1.21 |
* capacity, the specified access policy and initially containing the |
206 |
tim |
1.17 |
* elements of the given collection, |
207 |
dholmes |
1.16 |
* added in traversal order of the collection's iterator. |
208 |
jsr166 |
1.50 |
* |
209 |
dholmes |
1.16 |
* @param capacity the capacity of this queue |
210 |
jsr166 |
1.69 |
* @param fair if {@code true} then queue accesses for threads blocked |
211 |
jsr166 |
1.50 |
* on insertion or removal, are processed in FIFO order; |
212 |
jsr166 |
1.69 |
* if {@code false} the access order is unspecified. |
213 |
dholmes |
1.16 |
* @param c the collection of elements to initially contain |
214 |
jsr166 |
1.69 |
* @throws IllegalArgumentException if {@code capacity} is less than |
215 |
|
|
* {@code c.size()}, or less than 1. |
216 |
jsr166 |
1.50 |
* @throws NullPointerException if the specified collection or any |
217 |
|
|
* of its elements are null |
218 |
dholmes |
1.16 |
*/ |
219 |
tim |
1.20 |
public ArrayBlockingQueue(int capacity, boolean fair, |
220 |
dholmes |
1.18 |
Collection<? extends E> c) { |
221 |
dl |
1.36 |
this(capacity, fair); |
222 |
dholmes |
1.16 |
|
223 |
jsr166 |
1.68 |
final ReentrantLock lock = this.lock; |
224 |
|
|
lock.lock(); // Lock only for visibility, not mutual exclusion |
225 |
|
|
try { |
226 |
|
|
int i = 0; |
227 |
|
|
try { |
228 |
|
|
for (E e : c) { |
229 |
|
|
checkNotNull(e); |
230 |
|
|
items[i++] = e; |
231 |
|
|
} |
232 |
|
|
} catch (ArrayIndexOutOfBoundsException ex) { |
233 |
|
|
throw new IllegalArgumentException(); |
234 |
|
|
} |
235 |
|
|
count = i; |
236 |
|
|
putIndex = (i == capacity) ? 0 : i; |
237 |
|
|
} finally { |
238 |
|
|
lock.unlock(); |
239 |
|
|
} |
240 |
dholmes |
1.16 |
} |
241 |
dl |
1.2 |
|
242 |
dholmes |
1.13 |
/** |
243 |
jsr166 |
1.50 |
* Inserts the specified element at the tail of this queue if it is |
244 |
|
|
* possible to do so immediately without exceeding the queue's capacity, |
245 |
jsr166 |
1.69 |
* returning {@code true} upon success and throwing an |
246 |
|
|
* {@code IllegalStateException} if this queue is full. |
247 |
dl |
1.25 |
* |
248 |
jsr166 |
1.50 |
* @param e the element to add |
249 |
jsr166 |
1.69 |
* @return {@code true} (as specified by {@link Collection#add}) |
250 |
jsr166 |
1.50 |
* @throws IllegalStateException if this queue is full |
251 |
|
|
* @throws NullPointerException if the specified element is null |
252 |
|
|
*/ |
253 |
|
|
public boolean add(E e) { |
254 |
jsr166 |
1.56 |
return super.add(e); |
255 |
jsr166 |
1.50 |
} |
256 |
|
|
|
257 |
|
|
/** |
258 |
|
|
* Inserts the specified element at the tail of this queue if it is |
259 |
|
|
* possible to do so immediately without exceeding the queue's capacity, |
260 |
jsr166 |
1.69 |
* returning {@code true} upon success and {@code false} if this queue |
261 |
jsr166 |
1.50 |
* is full. This method is generally preferable to method {@link #add}, |
262 |
|
|
* which can fail to insert an element only by throwing an exception. |
263 |
|
|
* |
264 |
|
|
* @throws NullPointerException if the specified element is null |
265 |
dholmes |
1.13 |
*/ |
266 |
jsr166 |
1.49 |
public boolean offer(E e) { |
267 |
jsr166 |
1.68 |
checkNotNull(e); |
268 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
269 |
dl |
1.5 |
lock.lock(); |
270 |
|
|
try { |
271 |
jsr166 |
1.59 |
if (count == items.length) |
272 |
dl |
1.2 |
return false; |
273 |
dl |
1.5 |
else { |
274 |
jsr166 |
1.49 |
insert(e); |
275 |
dl |
1.5 |
return true; |
276 |
|
|
} |
277 |
tim |
1.23 |
} finally { |
278 |
tim |
1.12 |
lock.unlock(); |
279 |
dl |
1.2 |
} |
280 |
dl |
1.5 |
} |
281 |
dl |
1.2 |
|
282 |
dholmes |
1.13 |
/** |
283 |
jsr166 |
1.50 |
* Inserts the specified element at the tail of this queue, waiting |
284 |
|
|
* for space to become available if the queue is full. |
285 |
|
|
* |
286 |
|
|
* @throws InterruptedException {@inheritDoc} |
287 |
|
|
* @throws NullPointerException {@inheritDoc} |
288 |
|
|
*/ |
289 |
|
|
public void put(E e) throws InterruptedException { |
290 |
jsr166 |
1.68 |
checkNotNull(e); |
291 |
jsr166 |
1.50 |
final ReentrantLock lock = this.lock; |
292 |
|
|
lock.lockInterruptibly(); |
293 |
|
|
try { |
294 |
jsr166 |
1.59 |
while (count == items.length) |
295 |
jsr166 |
1.58 |
notFull.await(); |
296 |
jsr166 |
1.50 |
insert(e); |
297 |
|
|
} finally { |
298 |
|
|
lock.unlock(); |
299 |
|
|
} |
300 |
|
|
} |
301 |
|
|
|
302 |
|
|
/** |
303 |
|
|
* Inserts the specified element at the tail of this queue, waiting |
304 |
|
|
* up to the specified wait time for space to become available if |
305 |
|
|
* the queue is full. |
306 |
|
|
* |
307 |
|
|
* @throws InterruptedException {@inheritDoc} |
308 |
|
|
* @throws NullPointerException {@inheritDoc} |
309 |
brian |
1.7 |
*/ |
310 |
jsr166 |
1.49 |
public boolean offer(E e, long timeout, TimeUnit unit) |
311 |
dholmes |
1.13 |
throws InterruptedException { |
312 |
dl |
1.2 |
|
313 |
jsr166 |
1.68 |
checkNotNull(e); |
314 |
jsr166 |
1.56 |
long nanos = unit.toNanos(timeout); |
315 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
316 |
dl |
1.5 |
lock.lockInterruptibly(); |
317 |
|
|
try { |
318 |
jsr166 |
1.59 |
while (count == items.length) { |
319 |
dl |
1.5 |
if (nanos <= 0) |
320 |
|
|
return false; |
321 |
jsr166 |
1.58 |
nanos = notFull.awaitNanos(nanos); |
322 |
dl |
1.5 |
} |
323 |
jsr166 |
1.58 |
insert(e); |
324 |
|
|
return true; |
325 |
tim |
1.23 |
} finally { |
326 |
dl |
1.5 |
lock.unlock(); |
327 |
dl |
1.2 |
} |
328 |
dl |
1.5 |
} |
329 |
dl |
1.2 |
|
330 |
dholmes |
1.13 |
public E poll() { |
331 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
332 |
dholmes |
1.13 |
lock.lock(); |
333 |
|
|
try { |
334 |
jsr166 |
1.59 |
return (count == 0) ? null : extract(); |
335 |
tim |
1.23 |
} finally { |
336 |
tim |
1.15 |
lock.unlock(); |
337 |
dholmes |
1.13 |
} |
338 |
|
|
} |
339 |
|
|
|
340 |
jsr166 |
1.50 |
public E take() throws InterruptedException { |
341 |
|
|
final ReentrantLock lock = this.lock; |
342 |
|
|
lock.lockInterruptibly(); |
343 |
|
|
try { |
344 |
jsr166 |
1.59 |
while (count == 0) |
345 |
jsr166 |
1.58 |
notEmpty.await(); |
346 |
|
|
return extract(); |
347 |
jsr166 |
1.50 |
} finally { |
348 |
|
|
lock.unlock(); |
349 |
|
|
} |
350 |
|
|
} |
351 |
|
|
|
352 |
dl |
1.5 |
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
353 |
jsr166 |
1.56 |
long nanos = unit.toNanos(timeout); |
354 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
355 |
dl |
1.5 |
lock.lockInterruptibly(); |
356 |
|
|
try { |
357 |
jsr166 |
1.59 |
while (count == 0) { |
358 |
dl |
1.5 |
if (nanos <= 0) |
359 |
|
|
return null; |
360 |
jsr166 |
1.58 |
nanos = notEmpty.awaitNanos(nanos); |
361 |
dl |
1.2 |
} |
362 |
jsr166 |
1.58 |
return extract(); |
363 |
tim |
1.23 |
} finally { |
364 |
dl |
1.5 |
lock.unlock(); |
365 |
|
|
} |
366 |
|
|
} |
367 |
dl |
1.2 |
|
368 |
dholmes |
1.13 |
public E peek() { |
369 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
370 |
dholmes |
1.13 |
lock.lock(); |
371 |
|
|
try { |
372 |
jsr166 |
1.68 |
return (count == 0) ? null : itemAt(takeIndex); |
373 |
tim |
1.23 |
} finally { |
374 |
dholmes |
1.13 |
lock.unlock(); |
375 |
|
|
} |
376 |
|
|
} |
377 |
|
|
|
378 |
|
|
// this doc comment is overridden to remove the reference to collections |
379 |
|
|
// greater in size than Integer.MAX_VALUE |
380 |
tim |
1.15 |
/** |
381 |
dl |
1.25 |
* Returns the number of elements in this queue. |
382 |
|
|
* |
383 |
jsr166 |
1.50 |
* @return the number of elements in this queue |
384 |
dholmes |
1.13 |
*/ |
385 |
|
|
public int size() { |
386 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
387 |
dholmes |
1.13 |
lock.lock(); |
388 |
|
|
try { |
389 |
|
|
return count; |
390 |
tim |
1.23 |
} finally { |
391 |
dholmes |
1.13 |
lock.unlock(); |
392 |
|
|
} |
393 |
|
|
} |
394 |
|
|
|
395 |
|
|
// this doc comment is a modified copy of the inherited doc comment, |
396 |
|
|
// without the reference to unlimited queues. |
397 |
tim |
1.15 |
/** |
398 |
jsr166 |
1.48 |
* Returns the number of additional elements that this queue can ideally |
399 |
|
|
* (in the absence of memory or resource constraints) accept without |
400 |
dholmes |
1.13 |
* blocking. This is always equal to the initial capacity of this queue |
401 |
jsr166 |
1.69 |
* less the current {@code size} of this queue. |
402 |
jsr166 |
1.48 |
* |
403 |
|
|
* <p>Note that you <em>cannot</em> always tell if an attempt to insert |
404 |
jsr166 |
1.69 |
* an element will succeed by inspecting {@code remainingCapacity} |
405 |
jsr166 |
1.48 |
* because it may be the case that another thread is about to |
406 |
jsr166 |
1.50 |
* insert or remove an element. |
407 |
dholmes |
1.13 |
*/ |
408 |
|
|
public int remainingCapacity() { |
409 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
410 |
dholmes |
1.13 |
lock.lock(); |
411 |
|
|
try { |
412 |
|
|
return items.length - count; |
413 |
tim |
1.23 |
} finally { |
414 |
dholmes |
1.13 |
lock.unlock(); |
415 |
|
|
} |
416 |
|
|
} |
417 |
|
|
|
418 |
jsr166 |
1.50 |
/** |
419 |
|
|
* Removes a single instance of the specified element from this queue, |
420 |
jsr166 |
1.69 |
* if it is present. More formally, removes an element {@code e} such |
421 |
|
|
* that {@code o.equals(e)}, if this queue contains one or more such |
422 |
jsr166 |
1.50 |
* elements. |
423 |
jsr166 |
1.69 |
* Returns {@code true} if this queue contained the specified element |
424 |
jsr166 |
1.50 |
* (or equivalently, if this queue changed as a result of the call). |
425 |
|
|
* |
426 |
jsr166 |
1.64 |
* <p>Removal of interior elements in circular array based queues |
427 |
dl |
1.60 |
* is an intrinsically slow and disruptive operation, so should |
428 |
|
|
* be undertaken only in exceptional circumstances, ideally |
429 |
|
|
* only when the queue is known not to be accessible by other |
430 |
|
|
* threads. |
431 |
|
|
* |
432 |
jsr166 |
1.50 |
* @param o element to be removed from this queue, if present |
433 |
jsr166 |
1.69 |
* @return {@code true} if this queue changed as a result of the call |
434 |
jsr166 |
1.50 |
*/ |
435 |
|
|
public boolean remove(Object o) { |
436 |
|
|
if (o == null) return false; |
437 |
jsr166 |
1.68 |
final Object[] items = this.items; |
438 |
jsr166 |
1.50 |
final ReentrantLock lock = this.lock; |
439 |
|
|
lock.lock(); |
440 |
|
|
try { |
441 |
jsr166 |
1.68 |
for (int i = takeIndex, k = count; k > 0; i = inc(i), k--) { |
442 |
jsr166 |
1.50 |
if (o.equals(items[i])) { |
443 |
|
|
removeAt(i); |
444 |
|
|
return true; |
445 |
|
|
} |
446 |
|
|
} |
447 |
jsr166 |
1.68 |
return false; |
448 |
jsr166 |
1.50 |
} finally { |
449 |
|
|
lock.unlock(); |
450 |
|
|
} |
451 |
|
|
} |
452 |
dholmes |
1.13 |
|
453 |
jsr166 |
1.50 |
/** |
454 |
jsr166 |
1.69 |
* Returns {@code true} if this queue contains the specified element. |
455 |
|
|
* More formally, returns {@code true} if and only if this queue contains |
456 |
|
|
* at least one element {@code e} such that {@code o.equals(e)}. |
457 |
jsr166 |
1.50 |
* |
458 |
|
|
* @param o object to be checked for containment in this queue |
459 |
jsr166 |
1.69 |
* @return {@code true} if this queue contains the specified element |
460 |
jsr166 |
1.50 |
*/ |
461 |
dholmes |
1.21 |
public boolean contains(Object o) { |
462 |
|
|
if (o == null) return false; |
463 |
jsr166 |
1.68 |
final Object[] items = this.items; |
464 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
465 |
dl |
1.5 |
lock.lock(); |
466 |
|
|
try { |
467 |
jsr166 |
1.68 |
for (int i = takeIndex, k = count; k > 0; i = inc(i), k--) |
468 |
dholmes |
1.21 |
if (o.equals(items[i])) |
469 |
dl |
1.2 |
return true; |
470 |
|
|
return false; |
471 |
tim |
1.23 |
} finally { |
472 |
dl |
1.5 |
lock.unlock(); |
473 |
|
|
} |
474 |
|
|
} |
475 |
brian |
1.7 |
|
476 |
jsr166 |
1.50 |
/** |
477 |
|
|
* Returns an array containing all of the elements in this queue, in |
478 |
|
|
* proper sequence. |
479 |
|
|
* |
480 |
|
|
* <p>The returned array will be "safe" in that no references to it are |
481 |
|
|
* maintained by this queue. (In other words, this method must allocate |
482 |
|
|
* a new array). The caller is thus free to modify the returned array. |
483 |
jsr166 |
1.51 |
* |
484 |
jsr166 |
1.50 |
* <p>This method acts as bridge between array-based and collection-based |
485 |
|
|
* APIs. |
486 |
|
|
* |
487 |
|
|
* @return an array containing all of the elements in this queue |
488 |
|
|
*/ |
489 |
dl |
1.5 |
public Object[] toArray() { |
490 |
jsr166 |
1.68 |
final Object[] items = this.items; |
491 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
492 |
dl |
1.5 |
lock.lock(); |
493 |
|
|
try { |
494 |
jsr166 |
1.68 |
final int count = this.count; |
495 |
dl |
1.34 |
Object[] a = new Object[count]; |
496 |
jsr166 |
1.68 |
for (int i = takeIndex, k = 0; k < count; i = inc(i), k++) |
497 |
|
|
a[k] = items[i]; |
498 |
dl |
1.2 |
return a; |
499 |
tim |
1.23 |
} finally { |
500 |
dl |
1.5 |
lock.unlock(); |
501 |
|
|
} |
502 |
|
|
} |
503 |
brian |
1.7 |
|
504 |
jsr166 |
1.50 |
/** |
505 |
|
|
* Returns an array containing all of the elements in this queue, in |
506 |
|
|
* proper sequence; the runtime type of the returned array is that of |
507 |
|
|
* the specified array. If the queue fits in the specified array, it |
508 |
|
|
* is returned therein. Otherwise, a new array is allocated with the |
509 |
|
|
* runtime type of the specified array and the size of this queue. |
510 |
|
|
* |
511 |
|
|
* <p>If this queue fits in the specified array with room to spare |
512 |
|
|
* (i.e., the array has more elements than this queue), the element in |
513 |
|
|
* the array immediately following the end of the queue is set to |
514 |
jsr166 |
1.69 |
* {@code null}. |
515 |
jsr166 |
1.50 |
* |
516 |
|
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
517 |
|
|
* array-based and collection-based APIs. Further, this method allows |
518 |
|
|
* precise control over the runtime type of the output array, and may, |
519 |
|
|
* under certain circumstances, be used to save allocation costs. |
520 |
|
|
* |
521 |
jsr166 |
1.69 |
* <p>Suppose {@code x} is a queue known to contain only strings. |
522 |
jsr166 |
1.50 |
* The following code can be used to dump the queue into a newly |
523 |
jsr166 |
1.69 |
* allocated array of {@code String}: |
524 |
jsr166 |
1.50 |
* |
525 |
|
|
* <pre> |
526 |
|
|
* String[] y = x.toArray(new String[0]);</pre> |
527 |
|
|
* |
528 |
jsr166 |
1.69 |
* Note that {@code toArray(new Object[0])} is identical in function to |
529 |
|
|
* {@code toArray()}. |
530 |
jsr166 |
1.50 |
* |
531 |
|
|
* @param a the array into which the elements of the queue are to |
532 |
|
|
* be stored, if it is big enough; otherwise, a new array of the |
533 |
|
|
* same runtime type is allocated for this purpose |
534 |
|
|
* @return an array containing all of the elements in this queue |
535 |
|
|
* @throws ArrayStoreException if the runtime type of the specified array |
536 |
|
|
* is not a supertype of the runtime type of every element in |
537 |
|
|
* this queue |
538 |
|
|
* @throws NullPointerException if the specified array is null |
539 |
|
|
*/ |
540 |
jsr166 |
1.68 |
@SuppressWarnings("unchecked") |
541 |
dl |
1.5 |
public <T> T[] toArray(T[] a) { |
542 |
jsr166 |
1.68 |
final Object[] items = this.items; |
543 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
544 |
dl |
1.5 |
lock.lock(); |
545 |
|
|
try { |
546 |
jsr166 |
1.68 |
final int count = this.count; |
547 |
|
|
final int len = a.length; |
548 |
|
|
if (len < count) |
549 |
dholmes |
1.16 |
a = (T[])java.lang.reflect.Array.newInstance( |
550 |
jsr166 |
1.68 |
a.getClass().getComponentType(), count); |
551 |
|
|
for (int i = takeIndex, k = 0; k < count; i = inc(i), k++) |
552 |
|
|
a[k] = (T) items[i]; |
553 |
|
|
if (len > count) |
554 |
dl |
1.5 |
a[count] = null; |
555 |
dl |
1.2 |
return a; |
556 |
tim |
1.23 |
} finally { |
557 |
dl |
1.5 |
lock.unlock(); |
558 |
|
|
} |
559 |
|
|
} |
560 |
dl |
1.6 |
|
561 |
|
|
public String toString() { |
562 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
563 |
dl |
1.6 |
lock.lock(); |
564 |
|
|
try { |
565 |
jsr166 |
1.68 |
int k = count; |
566 |
|
|
if (k == 0) |
567 |
|
|
return "[]"; |
568 |
|
|
|
569 |
|
|
StringBuilder sb = new StringBuilder(); |
570 |
|
|
sb.append('['); |
571 |
|
|
for (int i = takeIndex; ; i = inc(i)) { |
572 |
|
|
Object e = items[i]; |
573 |
|
|
sb.append(e == this ? "(this Collection)" : e); |
574 |
|
|
if (--k == 0) |
575 |
|
|
return sb.append(']').toString(); |
576 |
|
|
sb.append(',').append(' '); |
577 |
|
|
} |
578 |
tim |
1.23 |
} finally { |
579 |
dl |
1.6 |
lock.unlock(); |
580 |
|
|
} |
581 |
|
|
} |
582 |
tim |
1.12 |
|
583 |
dl |
1.44 |
/** |
584 |
|
|
* Atomically removes all of the elements from this queue. |
585 |
|
|
* The queue will be empty after this call returns. |
586 |
|
|
*/ |
587 |
dl |
1.30 |
public void clear() { |
588 |
jsr166 |
1.68 |
final Object[] items = this.items; |
589 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
590 |
dl |
1.30 |
lock.lock(); |
591 |
|
|
try { |
592 |
jsr166 |
1.68 |
for (int i = takeIndex, k = count; k > 0; i = inc(i), k--) |
593 |
dl |
1.30 |
items[i] = null; |
594 |
|
|
count = 0; |
595 |
|
|
putIndex = 0; |
596 |
|
|
takeIndex = 0; |
597 |
|
|
notFull.signalAll(); |
598 |
|
|
} finally { |
599 |
|
|
lock.unlock(); |
600 |
|
|
} |
601 |
|
|
} |
602 |
|
|
|
603 |
jsr166 |
1.50 |
/** |
604 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
605 |
|
|
* @throws ClassCastException {@inheritDoc} |
606 |
|
|
* @throws NullPointerException {@inheritDoc} |
607 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
608 |
|
|
*/ |
609 |
dl |
1.30 |
public int drainTo(Collection<? super E> c) { |
610 |
jsr166 |
1.68 |
checkNotNull(c); |
611 |
dl |
1.30 |
if (c == this) |
612 |
|
|
throw new IllegalArgumentException(); |
613 |
jsr166 |
1.68 |
final Object[] items = this.items; |
614 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
615 |
dl |
1.30 |
lock.lock(); |
616 |
|
|
try { |
617 |
|
|
int i = takeIndex; |
618 |
|
|
int n = 0; |
619 |
|
|
int max = count; |
620 |
|
|
while (n < max) { |
621 |
jsr166 |
1.70 |
c.add(this.<E>cast(items[i])); |
622 |
dl |
1.30 |
items[i] = null; |
623 |
|
|
i = inc(i); |
624 |
|
|
++n; |
625 |
|
|
} |
626 |
|
|
if (n > 0) { |
627 |
|
|
count = 0; |
628 |
|
|
putIndex = 0; |
629 |
|
|
takeIndex = 0; |
630 |
|
|
notFull.signalAll(); |
631 |
|
|
} |
632 |
|
|
return n; |
633 |
|
|
} finally { |
634 |
|
|
lock.unlock(); |
635 |
|
|
} |
636 |
|
|
} |
637 |
|
|
|
638 |
jsr166 |
1.50 |
/** |
639 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
640 |
|
|
* @throws ClassCastException {@inheritDoc} |
641 |
|
|
* @throws NullPointerException {@inheritDoc} |
642 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
643 |
|
|
*/ |
644 |
dl |
1.30 |
public int drainTo(Collection<? super E> c, int maxElements) { |
645 |
jsr166 |
1.68 |
checkNotNull(c); |
646 |
dl |
1.30 |
if (c == this) |
647 |
|
|
throw new IllegalArgumentException(); |
648 |
|
|
if (maxElements <= 0) |
649 |
|
|
return 0; |
650 |
jsr166 |
1.68 |
final Object[] items = this.items; |
651 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
652 |
dl |
1.30 |
lock.lock(); |
653 |
|
|
try { |
654 |
|
|
int i = takeIndex; |
655 |
|
|
int n = 0; |
656 |
jsr166 |
1.58 |
int max = (maxElements < count) ? maxElements : count; |
657 |
dl |
1.30 |
while (n < max) { |
658 |
jsr166 |
1.70 |
c.add(this.<E>cast(items[i])); |
659 |
dl |
1.30 |
items[i] = null; |
660 |
|
|
i = inc(i); |
661 |
|
|
++n; |
662 |
|
|
} |
663 |
|
|
if (n > 0) { |
664 |
|
|
count -= n; |
665 |
|
|
takeIndex = i; |
666 |
|
|
notFull.signalAll(); |
667 |
|
|
} |
668 |
|
|
return n; |
669 |
|
|
} finally { |
670 |
|
|
lock.unlock(); |
671 |
|
|
} |
672 |
|
|
} |
673 |
|
|
|
674 |
brian |
1.7 |
/** |
675 |
dl |
1.75 |
* Returns an iterator over the elements in this queue in proper sequence. |
676 |
jsr166 |
1.77 |
* The elements will be returned in order from first (head) to last (tail). |
677 |
|
|
* |
678 |
|
|
* <p>The returned {@code Iterator} is a "weakly consistent" iterator that |
679 |
|
|
* will never throw {@link java.util.ConcurrentModificationException |
680 |
|
|
* ConcurrentModificationException}, |
681 |
dl |
1.75 |
* and guarantees to traverse elements as they existed upon |
682 |
|
|
* construction of the iterator, and may (but is not guaranteed to) |
683 |
|
|
* reflect any modifications subsequent to construction. |
684 |
brian |
1.7 |
* |
685 |
jsr166 |
1.50 |
* @return an iterator over the elements in this queue in proper sequence |
686 |
brian |
1.7 |
*/ |
687 |
dl |
1.5 |
public Iterator<E> iterator() { |
688 |
jsr166 |
1.68 |
return new Itr(); |
689 |
dl |
1.5 |
} |
690 |
dl |
1.8 |
|
691 |
|
|
/** |
692 |
dl |
1.60 |
* Iterator for ArrayBlockingQueue. To maintain weak consistency |
693 |
|
|
* with respect to puts and takes, we (1) read ahead one slot, so |
694 |
|
|
* as to not report hasNext true but then not have an element to |
695 |
dl |
1.75 |
* return -- however we later recheck this slot to use the most |
696 |
|
|
* current value; (2) ensure that each array slot is traversed at |
697 |
|
|
* most once (by tracking "remaining" elements); (3) skip over |
698 |
|
|
* null slots, which can occur if takes race ahead of iterators. |
699 |
dl |
1.60 |
* However, for circular array-based queues, we cannot rely on any |
700 |
|
|
* well established definition of what it means to be weakly |
701 |
|
|
* consistent with respect to interior removes since these may |
702 |
|
|
* require slot overwrites in the process of sliding elements to |
703 |
|
|
* cover gaps. So we settle for resiliency, operating on |
704 |
jsr166 |
1.62 |
* established apparent nexts, which may miss some elements that |
705 |
dl |
1.66 |
* have moved between calls to next. |
706 |
dl |
1.8 |
*/ |
707 |
dl |
1.5 |
private class Itr implements Iterator<E> { |
708 |
dl |
1.60 |
private int remaining; // Number of elements yet to be returned |
709 |
|
|
private int nextIndex; // Index of element to be returned by next |
710 |
|
|
private E nextItem; // Element to be returned by next call to next |
711 |
|
|
private E lastItem; // Element returned by last call to next |
712 |
|
|
private int lastRet; // Index of last element returned, or -1 if none |
713 |
tim |
1.12 |
|
714 |
dl |
1.66 |
Itr() { |
715 |
jsr166 |
1.68 |
final ReentrantLock lock = ArrayBlockingQueue.this.lock; |
716 |
|
|
lock.lock(); |
717 |
|
|
try { |
718 |
|
|
lastRet = -1; |
719 |
|
|
if ((remaining = count) > 0) |
720 |
|
|
nextItem = itemAt(nextIndex = takeIndex); |
721 |
|
|
} finally { |
722 |
|
|
lock.unlock(); |
723 |
|
|
} |
724 |
dl |
1.5 |
} |
725 |
tim |
1.12 |
|
726 |
dl |
1.5 |
public boolean hasNext() { |
727 |
dl |
1.60 |
return remaining > 0; |
728 |
dl |
1.5 |
} |
729 |
tim |
1.12 |
|
730 |
dl |
1.5 |
public E next() { |
731 |
dl |
1.66 |
final ReentrantLock lock = ArrayBlockingQueue.this.lock; |
732 |
|
|
lock.lock(); |
733 |
|
|
try { |
734 |
dl |
1.67 |
if (remaining <= 0) |
735 |
|
|
throw new NoSuchElementException(); |
736 |
dl |
1.66 |
lastRet = nextIndex; |
737 |
dl |
1.75 |
E x = itemAt(nextIndex); // check for fresher value |
738 |
|
|
if (x == null) { |
739 |
|
|
x = nextItem; // we are forced to report old value |
740 |
|
|
lastItem = null; // but ensure remove fails |
741 |
dl |
1.66 |
} |
742 |
dl |
1.75 |
else |
743 |
|
|
lastItem = x; |
744 |
|
|
while (--remaining > 0 && // skip over nulls |
745 |
|
|
(nextItem = itemAt(nextIndex = inc(nextIndex))) == null) |
746 |
|
|
; |
747 |
dl |
1.66 |
return x; |
748 |
|
|
} finally { |
749 |
|
|
lock.unlock(); |
750 |
dl |
1.2 |
} |
751 |
dl |
1.5 |
} |
752 |
tim |
1.12 |
|
753 |
dl |
1.5 |
public void remove() { |
754 |
dl |
1.36 |
final ReentrantLock lock = ArrayBlockingQueue.this.lock; |
755 |
dl |
1.5 |
lock.lock(); |
756 |
|
|
try { |
757 |
dl |
1.66 |
int i = lastRet; |
758 |
|
|
if (i == -1) |
759 |
|
|
throw new IllegalStateException(); |
760 |
dl |
1.2 |
lastRet = -1; |
761 |
jsr166 |
1.61 |
E x = lastItem; |
762 |
|
|
lastItem = null; |
763 |
jsr166 |
1.71 |
// only remove if item still at index |
764 |
dl |
1.75 |
if (x != null && x == items[i]) { |
765 |
jsr166 |
1.71 |
boolean removingHead = (i == takeIndex); |
766 |
|
|
removeAt(i); |
767 |
|
|
if (!removingHead) |
768 |
|
|
nextIndex = dec(nextIndex); |
769 |
|
|
} |
770 |
tim |
1.23 |
} finally { |
771 |
dl |
1.5 |
lock.unlock(); |
772 |
|
|
} |
773 |
|
|
} |
774 |
tim |
1.1 |
} |
775 |
dl |
1.60 |
|
776 |
tim |
1.1 |
} |