1 |
dl |
1.2 |
/* |
2 |
|
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
dl |
1.23 |
* Expert Group and released to the public domain, as explained at |
4 |
jsr166 |
1.52 |
* http://creativecommons.org/publicdomain/zero/1.0/ |
5 |
dl |
1.2 |
*/ |
6 |
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|
7 |
jsr166 |
1.50 |
|
8 |
tim |
1.1 |
package java.util.concurrent; |
9 |
dl |
1.5 |
import java.util.concurrent.locks.*; |
10 |
tim |
1.1 |
import java.util.*; |
11 |
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|
12 |
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/** |
13 |
dl |
1.27 |
* An unbounded {@linkplain BlockingQueue blocking queue} of |
14 |
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* <tt>Delayed</tt> elements, in which an element can only be taken |
15 |
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* when its delay has expired. The <em>head</em> of the queue is that |
16 |
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* <tt>Delayed</tt> element whose delay expired furthest in the |
17 |
jsr166 |
1.32 |
* past. If no delay has expired there is no head and <tt>poll</tt> |
18 |
dl |
1.27 |
* will return <tt>null</tt>. Expiration occurs when an element's |
19 |
|
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* <tt>getDelay(TimeUnit.NANOSECONDS)</tt> method returns a value less |
20 |
dl |
1.36 |
* than or equal to zero. Even though unexpired elements cannot be |
21 |
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* removed using <tt>take</tt> or <tt>poll</tt>, they are otherwise |
22 |
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* treated as normal elements. For example, the <tt>size</tt> method |
23 |
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* returns the count of both expired and unexpired elements. |
24 |
jsr166 |
1.39 |
* This queue does not permit null elements. |
25 |
dl |
1.25 |
* |
26 |
dl |
1.26 |
* <p>This class and its iterator implement all of the |
27 |
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* <em>optional</em> methods of the {@link Collection} and {@link |
28 |
dl |
1.53 |
* Iterator} interfaces. The Iterator provided in method {@link |
29 |
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* #iterator()} is <em>not</em> guaranteed to traverse the elements of |
30 |
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* the DelayQueue in any particular order. |
31 |
dl |
1.26 |
* |
32 |
dl |
1.25 |
* <p>This class is a member of the |
33 |
jsr166 |
1.46 |
* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
34 |
dl |
1.25 |
* Java Collections Framework</a>. |
35 |
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* |
36 |
dl |
1.4 |
* @since 1.5 |
37 |
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* @author Doug Lea |
38 |
dl |
1.20 |
* @param <E> the type of elements held in this collection |
39 |
dl |
1.19 |
*/ |
40 |
tim |
1.1 |
|
41 |
dl |
1.3 |
public class DelayQueue<E extends Delayed> extends AbstractQueue<E> |
42 |
|
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implements BlockingQueue<E> { |
43 |
tim |
1.6 |
|
44 |
dl |
1.2 |
private transient final ReentrantLock lock = new ReentrantLock(); |
45 |
dl |
1.3 |
private final PriorityQueue<E> q = new PriorityQueue<E>(); |
46 |
tim |
1.1 |
|
47 |
dl |
1.4 |
/** |
48 |
jsr166 |
1.48 |
* Thread designated to wait for the element at the head of |
49 |
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* the queue. This variant of the Leader-Follower pattern |
50 |
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* (http://www.cs.wustl.edu/~schmidt/POSA/POSA2/) serves to |
51 |
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* minimize unnecessary timed waiting. When a thread becomes |
52 |
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* the leader, it waits only for the next delay to elapse, but |
53 |
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* other threads await indefinitely. The leader thread must |
54 |
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* signal some other thread before returning from take() or |
55 |
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* poll(...), unless some other thread becomes leader in the |
56 |
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* interim. Whenever the head of the queue is replaced with |
57 |
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* an element with an earlier expiration time, the leader |
58 |
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* field is invalidated by being reset to null, and some |
59 |
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* waiting thread, but not necessarily the current leader, is |
60 |
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* signalled. So waiting threads must be prepared to acquire |
61 |
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* and lose leadership while waiting. |
62 |
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*/ |
63 |
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private Thread leader = null; |
64 |
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|
65 |
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/** |
66 |
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* Condition signalled when a newer element becomes available |
67 |
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* at the head of the queue or a new thread may need to |
68 |
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* become leader. |
69 |
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*/ |
70 |
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private final Condition available = lock.newCondition(); |
71 |
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|
72 |
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/** |
73 |
dholmes |
1.7 |
* Creates a new <tt>DelayQueue</tt> that is initially empty. |
74 |
dl |
1.4 |
*/ |
75 |
tim |
1.1 |
public DelayQueue() {} |
76 |
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|
77 |
tim |
1.6 |
/** |
78 |
tim |
1.9 |
* Creates a <tt>DelayQueue</tt> initially containing the elements of the |
79 |
dholmes |
1.7 |
* given collection of {@link Delayed} instances. |
80 |
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* |
81 |
jsr166 |
1.32 |
* @param c the collection of elements to initially contain |
82 |
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* @throws NullPointerException if the specified collection or any |
83 |
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* of its elements are null |
84 |
tim |
1.6 |
*/ |
85 |
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public DelayQueue(Collection<? extends E> c) { |
86 |
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this.addAll(c); |
87 |
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} |
88 |
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|
89 |
dholmes |
1.7 |
/** |
90 |
dl |
1.16 |
* Inserts the specified element into this delay queue. |
91 |
dholmes |
1.7 |
* |
92 |
jsr166 |
1.30 |
* @param e the element to add |
93 |
jsr166 |
1.38 |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
94 |
jsr166 |
1.32 |
* @throws NullPointerException if the specified element is null |
95 |
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*/ |
96 |
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public boolean add(E e) { |
97 |
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return offer(e); |
98 |
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} |
99 |
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100 |
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/** |
101 |
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* Inserts the specified element into this delay queue. |
102 |
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* |
103 |
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* @param e the element to add |
104 |
dholmes |
1.7 |
* @return <tt>true</tt> |
105 |
jsr166 |
1.32 |
* @throws NullPointerException if the specified element is null |
106 |
dholmes |
1.7 |
*/ |
107 |
jsr166 |
1.30 |
public boolean offer(E e) { |
108 |
dl |
1.21 |
final ReentrantLock lock = this.lock; |
109 |
dl |
1.2 |
lock.lock(); |
110 |
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try { |
111 |
jsr166 |
1.30 |
q.offer(e); |
112 |
jsr166 |
1.48 |
if (q.peek() == e) { |
113 |
jsr166 |
1.49 |
leader = null; |
114 |
jsr166 |
1.48 |
available.signal(); |
115 |
jsr166 |
1.49 |
} |
116 |
dl |
1.2 |
return true; |
117 |
tim |
1.13 |
} finally { |
118 |
dl |
1.2 |
lock.unlock(); |
119 |
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} |
120 |
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} |
121 |
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|
122 |
dholmes |
1.7 |
/** |
123 |
jsr166 |
1.32 |
* Inserts the specified element into this delay queue. As the queue is |
124 |
dholmes |
1.7 |
* unbounded this method will never block. |
125 |
jsr166 |
1.32 |
* |
126 |
jsr166 |
1.30 |
* @param e the element to add |
127 |
jsr166 |
1.32 |
* @throws NullPointerException {@inheritDoc} |
128 |
dholmes |
1.7 |
*/ |
129 |
jsr166 |
1.30 |
public void put(E e) { |
130 |
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offer(e); |
131 |
dl |
1.2 |
} |
132 |
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|
133 |
dholmes |
1.7 |
/** |
134 |
dl |
1.16 |
* Inserts the specified element into this delay queue. As the queue is |
135 |
dholmes |
1.7 |
* unbounded this method will never block. |
136 |
jsr166 |
1.32 |
* |
137 |
jsr166 |
1.30 |
* @param e the element to add |
138 |
dl |
1.14 |
* @param timeout This parameter is ignored as the method never blocks |
139 |
dholmes |
1.7 |
* @param unit This parameter is ignored as the method never blocks |
140 |
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* @return <tt>true</tt> |
141 |
jsr166 |
1.32 |
* @throws NullPointerException {@inheritDoc} |
142 |
dholmes |
1.7 |
*/ |
143 |
jsr166 |
1.30 |
public boolean offer(E e, long timeout, TimeUnit unit) { |
144 |
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return offer(e); |
145 |
dl |
1.2 |
} |
146 |
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|
147 |
dholmes |
1.7 |
/** |
148 |
jsr166 |
1.32 |
* Retrieves and removes the head of this queue, or returns <tt>null</tt> |
149 |
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* if this queue has no elements with an expired delay. |
150 |
dholmes |
1.7 |
* |
151 |
jsr166 |
1.32 |
* @return the head of this queue, or <tt>null</tt> if this |
152 |
|
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* queue has no elements with an expired delay |
153 |
dholmes |
1.7 |
*/ |
154 |
jsr166 |
1.32 |
public E poll() { |
155 |
|
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final ReentrantLock lock = this.lock; |
156 |
|
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lock.lock(); |
157 |
|
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try { |
158 |
|
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E first = q.peek(); |
159 |
|
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if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0) |
160 |
|
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return null; |
161 |
jsr166 |
1.48 |
else |
162 |
|
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return q.poll(); |
163 |
jsr166 |
1.32 |
} finally { |
164 |
|
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lock.unlock(); |
165 |
|
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} |
166 |
dl |
1.2 |
} |
167 |
|
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|
168 |
dl |
1.27 |
/** |
169 |
jsr166 |
1.32 |
* Retrieves and removes the head of this queue, waiting if necessary |
170 |
|
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* until an element with an expired delay is available on this queue. |
171 |
|
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* |
172 |
dl |
1.27 |
* @return the head of this queue |
173 |
jsr166 |
1.32 |
* @throws InterruptedException {@inheritDoc} |
174 |
dl |
1.27 |
*/ |
175 |
dl |
1.3 |
public E take() throws InterruptedException { |
176 |
dl |
1.21 |
final ReentrantLock lock = this.lock; |
177 |
dl |
1.2 |
lock.lockInterruptibly(); |
178 |
|
|
try { |
179 |
|
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for (;;) { |
180 |
dl |
1.3 |
E first = q.peek(); |
181 |
jsr166 |
1.48 |
if (first == null) |
182 |
dl |
1.4 |
available.await(); |
183 |
jsr166 |
1.49 |
else { |
184 |
jsr166 |
1.48 |
long delay = first.getDelay(TimeUnit.NANOSECONDS); |
185 |
jsr166 |
1.49 |
if (delay <= 0) |
186 |
|
|
return q.poll(); |
187 |
|
|
else if (leader != null) |
188 |
|
|
available.await(); |
189 |
|
|
else { |
190 |
|
|
Thread thisThread = Thread.currentThread(); |
191 |
|
|
leader = thisThread; |
192 |
|
|
try { |
193 |
|
|
available.awaitNanos(delay); |
194 |
|
|
} finally { |
195 |
|
|
if (leader == thisThread) |
196 |
|
|
leader = null; |
197 |
|
|
} |
198 |
dl |
1.2 |
} |
199 |
|
|
} |
200 |
|
|
} |
201 |
tim |
1.13 |
} finally { |
202 |
jsr166 |
1.49 |
if (leader == null && q.peek() != null) |
203 |
|
|
available.signal(); |
204 |
dl |
1.2 |
lock.unlock(); |
205 |
|
|
} |
206 |
|
|
} |
207 |
|
|
|
208 |
dl |
1.27 |
/** |
209 |
jsr166 |
1.32 |
* Retrieves and removes the head of this queue, waiting if necessary |
210 |
|
|
* until an element with an expired delay is available on this queue, |
211 |
|
|
* or the specified wait time expires. |
212 |
|
|
* |
213 |
dl |
1.27 |
* @return the head of this queue, or <tt>null</tt> if the |
214 |
jsr166 |
1.32 |
* specified waiting time elapses before an element with |
215 |
|
|
* an expired delay becomes available |
216 |
|
|
* @throws InterruptedException {@inheritDoc} |
217 |
dl |
1.27 |
*/ |
218 |
|
|
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
219 |
jsr166 |
1.41 |
long nanos = unit.toNanos(timeout); |
220 |
dl |
1.21 |
final ReentrantLock lock = this.lock; |
221 |
dl |
1.2 |
lock.lockInterruptibly(); |
222 |
|
|
try { |
223 |
|
|
for (;;) { |
224 |
dl |
1.3 |
E first = q.peek(); |
225 |
dl |
1.2 |
if (first == null) { |
226 |
|
|
if (nanos <= 0) |
227 |
|
|
return null; |
228 |
|
|
else |
229 |
dl |
1.4 |
nanos = available.awaitNanos(nanos); |
230 |
tim |
1.13 |
} else { |
231 |
jsr166 |
1.41 |
long delay = first.getDelay(TimeUnit.NANOSECONDS); |
232 |
jsr166 |
1.49 |
if (delay <= 0) |
233 |
|
|
return q.poll(); |
234 |
|
|
if (nanos <= 0) |
235 |
|
|
return null; |
236 |
|
|
if (nanos < delay || leader != null) |
237 |
|
|
nanos = available.awaitNanos(nanos); |
238 |
|
|
else { |
239 |
|
|
Thread thisThread = Thread.currentThread(); |
240 |
|
|
leader = thisThread; |
241 |
|
|
try { |
242 |
|
|
long timeLeft = available.awaitNanos(delay); |
243 |
|
|
nanos -= delay - timeLeft; |
244 |
|
|
} finally { |
245 |
|
|
if (leader == thisThread) |
246 |
|
|
leader = null; |
247 |
|
|
} |
248 |
|
|
} |
249 |
dl |
1.2 |
} |
250 |
|
|
} |
251 |
tim |
1.13 |
} finally { |
252 |
jsr166 |
1.49 |
if (leader == null && q.peek() != null) |
253 |
|
|
available.signal(); |
254 |
dl |
1.2 |
lock.unlock(); |
255 |
|
|
} |
256 |
|
|
} |
257 |
|
|
|
258 |
dl |
1.27 |
/** |
259 |
dl |
1.36 |
* Retrieves, but does not remove, the head of this queue, or |
260 |
|
|
* returns <tt>null</tt> if this queue is empty. Unlike |
261 |
|
|
* <tt>poll</tt>, if no expired elements are available in the queue, |
262 |
|
|
* this method returns the element that will expire next, |
263 |
|
|
* if one exists. |
264 |
dl |
1.27 |
* |
265 |
jsr166 |
1.32 |
* @return the head of this queue, or <tt>null</tt> if this |
266 |
dl |
1.35 |
* queue is empty. |
267 |
dl |
1.27 |
*/ |
268 |
dl |
1.3 |
public E peek() { |
269 |
dl |
1.21 |
final ReentrantLock lock = this.lock; |
270 |
dl |
1.2 |
lock.lock(); |
271 |
|
|
try { |
272 |
|
|
return q.peek(); |
273 |
tim |
1.13 |
} finally { |
274 |
dl |
1.2 |
lock.unlock(); |
275 |
|
|
} |
276 |
tim |
1.1 |
} |
277 |
|
|
|
278 |
dl |
1.2 |
public int size() { |
279 |
dl |
1.21 |
final ReentrantLock lock = this.lock; |
280 |
dl |
1.2 |
lock.lock(); |
281 |
|
|
try { |
282 |
|
|
return q.size(); |
283 |
tim |
1.13 |
} finally { |
284 |
dl |
1.2 |
lock.unlock(); |
285 |
|
|
} |
286 |
|
|
} |
287 |
|
|
|
288 |
jsr166 |
1.32 |
/** |
289 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
290 |
|
|
* @throws ClassCastException {@inheritDoc} |
291 |
|
|
* @throws NullPointerException {@inheritDoc} |
292 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
293 |
|
|
*/ |
294 |
dl |
1.17 |
public int drainTo(Collection<? super E> c) { |
295 |
|
|
if (c == null) |
296 |
|
|
throw new NullPointerException(); |
297 |
|
|
if (c == this) |
298 |
|
|
throw new IllegalArgumentException(); |
299 |
dl |
1.21 |
final ReentrantLock lock = this.lock; |
300 |
dl |
1.17 |
lock.lock(); |
301 |
|
|
try { |
302 |
|
|
int n = 0; |
303 |
|
|
for (;;) { |
304 |
|
|
E first = q.peek(); |
305 |
|
|
if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0) |
306 |
|
|
break; |
307 |
|
|
c.add(q.poll()); |
308 |
|
|
++n; |
309 |
|
|
} |
310 |
|
|
return n; |
311 |
|
|
} finally { |
312 |
|
|
lock.unlock(); |
313 |
|
|
} |
314 |
|
|
} |
315 |
|
|
|
316 |
jsr166 |
1.32 |
/** |
317 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
318 |
|
|
* @throws ClassCastException {@inheritDoc} |
319 |
|
|
* @throws NullPointerException {@inheritDoc} |
320 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
321 |
|
|
*/ |
322 |
dl |
1.17 |
public int drainTo(Collection<? super E> c, int maxElements) { |
323 |
|
|
if (c == null) |
324 |
|
|
throw new NullPointerException(); |
325 |
|
|
if (c == this) |
326 |
|
|
throw new IllegalArgumentException(); |
327 |
|
|
if (maxElements <= 0) |
328 |
|
|
return 0; |
329 |
dl |
1.21 |
final ReentrantLock lock = this.lock; |
330 |
dl |
1.17 |
lock.lock(); |
331 |
|
|
try { |
332 |
|
|
int n = 0; |
333 |
|
|
while (n < maxElements) { |
334 |
|
|
E first = q.peek(); |
335 |
|
|
if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0) |
336 |
|
|
break; |
337 |
|
|
c.add(q.poll()); |
338 |
|
|
++n; |
339 |
|
|
} |
340 |
|
|
return n; |
341 |
|
|
} finally { |
342 |
|
|
lock.unlock(); |
343 |
|
|
} |
344 |
|
|
} |
345 |
|
|
|
346 |
dholmes |
1.7 |
/** |
347 |
|
|
* Atomically removes all of the elements from this delay queue. |
348 |
|
|
* The queue will be empty after this call returns. |
349 |
jsr166 |
1.32 |
* Elements with an unexpired delay are not waited for; they are |
350 |
|
|
* simply discarded from the queue. |
351 |
dholmes |
1.7 |
*/ |
352 |
dl |
1.2 |
public void clear() { |
353 |
dl |
1.21 |
final ReentrantLock lock = this.lock; |
354 |
dl |
1.2 |
lock.lock(); |
355 |
|
|
try { |
356 |
|
|
q.clear(); |
357 |
tim |
1.13 |
} finally { |
358 |
dl |
1.2 |
lock.unlock(); |
359 |
|
|
} |
360 |
|
|
} |
361 |
tim |
1.1 |
|
362 |
dholmes |
1.7 |
/** |
363 |
|
|
* Always returns <tt>Integer.MAX_VALUE</tt> because |
364 |
|
|
* a <tt>DelayQueue</tt> is not capacity constrained. |
365 |
jsr166 |
1.32 |
* |
366 |
dholmes |
1.7 |
* @return <tt>Integer.MAX_VALUE</tt> |
367 |
|
|
*/ |
368 |
dl |
1.2 |
public int remainingCapacity() { |
369 |
|
|
return Integer.MAX_VALUE; |
370 |
tim |
1.1 |
} |
371 |
dl |
1.2 |
|
372 |
jsr166 |
1.32 |
/** |
373 |
|
|
* Returns an array containing all of the elements in this queue. |
374 |
|
|
* The returned array elements are in no particular order. |
375 |
|
|
* |
376 |
|
|
* <p>The returned array will be "safe" in that no references to it are |
377 |
|
|
* maintained by this queue. (In other words, this method must allocate |
378 |
|
|
* a new array). The caller is thus free to modify the returned array. |
379 |
jsr166 |
1.33 |
* |
380 |
jsr166 |
1.32 |
* <p>This method acts as bridge between array-based and collection-based |
381 |
|
|
* APIs. |
382 |
|
|
* |
383 |
|
|
* @return an array containing all of the elements in this queue |
384 |
|
|
*/ |
385 |
dl |
1.2 |
public Object[] toArray() { |
386 |
dl |
1.21 |
final ReentrantLock lock = this.lock; |
387 |
dl |
1.2 |
lock.lock(); |
388 |
|
|
try { |
389 |
|
|
return q.toArray(); |
390 |
tim |
1.13 |
} finally { |
391 |
dl |
1.2 |
lock.unlock(); |
392 |
|
|
} |
393 |
tim |
1.1 |
} |
394 |
dl |
1.2 |
|
395 |
jsr166 |
1.32 |
/** |
396 |
|
|
* Returns an array containing all of the elements in this queue; the |
397 |
|
|
* runtime type of the returned array is that of the specified array. |
398 |
|
|
* The returned array elements are in no particular order. |
399 |
|
|
* If the queue fits in the specified array, it is returned therein. |
400 |
|
|
* Otherwise, a new array is allocated with the runtime type of the |
401 |
|
|
* specified array and the size of this queue. |
402 |
|
|
* |
403 |
|
|
* <p>If this queue fits in the specified array with room to spare |
404 |
|
|
* (i.e., the array has more elements than this queue), the element in |
405 |
|
|
* the array immediately following the end of the queue is set to |
406 |
|
|
* <tt>null</tt>. |
407 |
|
|
* |
408 |
|
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
409 |
|
|
* array-based and collection-based APIs. Further, this method allows |
410 |
|
|
* precise control over the runtime type of the output array, and may, |
411 |
|
|
* under certain circumstances, be used to save allocation costs. |
412 |
|
|
* |
413 |
jsr166 |
1.37 |
* <p>The following code can be used to dump a delay queue into a newly |
414 |
|
|
* allocated array of <tt>Delayed</tt>: |
415 |
jsr166 |
1.32 |
* |
416 |
|
|
* <pre> |
417 |
jsr166 |
1.37 |
* Delayed[] a = q.toArray(new Delayed[0]);</pre> |
418 |
jsr166 |
1.32 |
* |
419 |
|
|
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
420 |
|
|
* <tt>toArray()</tt>. |
421 |
|
|
* |
422 |
|
|
* @param a the array into which the elements of the queue are to |
423 |
|
|
* be stored, if it is big enough; otherwise, a new array of the |
424 |
|
|
* same runtime type is allocated for this purpose |
425 |
|
|
* @return an array containing all of the elements in this queue |
426 |
|
|
* @throws ArrayStoreException if the runtime type of the specified array |
427 |
|
|
* is not a supertype of the runtime type of every element in |
428 |
|
|
* this queue |
429 |
|
|
* @throws NullPointerException if the specified array is null |
430 |
|
|
*/ |
431 |
|
|
public <T> T[] toArray(T[] a) { |
432 |
dl |
1.21 |
final ReentrantLock lock = this.lock; |
433 |
dl |
1.2 |
lock.lock(); |
434 |
|
|
try { |
435 |
jsr166 |
1.32 |
return q.toArray(a); |
436 |
tim |
1.13 |
} finally { |
437 |
dl |
1.2 |
lock.unlock(); |
438 |
|
|
} |
439 |
tim |
1.1 |
} |
440 |
|
|
|
441 |
dl |
1.26 |
/** |
442 |
|
|
* Removes a single instance of the specified element from this |
443 |
dl |
1.36 |
* queue, if it is present, whether or not it has expired. |
444 |
dl |
1.26 |
*/ |
445 |
dholmes |
1.7 |
public boolean remove(Object o) { |
446 |
dl |
1.21 |
final ReentrantLock lock = this.lock; |
447 |
dl |
1.2 |
lock.lock(); |
448 |
|
|
try { |
449 |
dholmes |
1.7 |
return q.remove(o); |
450 |
tim |
1.13 |
} finally { |
451 |
dl |
1.2 |
lock.unlock(); |
452 |
|
|
} |
453 |
|
|
} |
454 |
|
|
|
455 |
dholmes |
1.7 |
/** |
456 |
dl |
1.36 |
* Returns an iterator over all the elements (both expired and |
457 |
dl |
1.44 |
* unexpired) in this queue. The iterator does not return the |
458 |
jsr166 |
1.51 |
* elements in any particular order. |
459 |
|
|
* |
460 |
|
|
* <p>The returned iterator is a "weakly consistent" iterator that |
461 |
|
|
* will never throw {@link java.util.ConcurrentModificationException |
462 |
|
|
* ConcurrentModificationException}, and guarantees to traverse |
463 |
|
|
* elements as they existed upon construction of the iterator, and |
464 |
|
|
* may (but is not guaranteed to) reflect any modifications |
465 |
|
|
* subsequent to construction. |
466 |
dholmes |
1.7 |
* |
467 |
jsr166 |
1.32 |
* @return an iterator over the elements in this queue |
468 |
dholmes |
1.7 |
*/ |
469 |
dl |
1.3 |
public Iterator<E> iterator() { |
470 |
dl |
1.44 |
return new Itr(toArray()); |
471 |
dl |
1.2 |
} |
472 |
|
|
|
473 |
dl |
1.42 |
/** |
474 |
|
|
* Snapshot iterator that works off copy of underlying q array. |
475 |
|
|
*/ |
476 |
dl |
1.44 |
private class Itr implements Iterator<E> { |
477 |
dl |
1.42 |
final Object[] array; // Array of all elements |
478 |
jsr166 |
1.49 |
int cursor; // index of next element to return; |
479 |
|
|
int lastRet; // index of last element, or -1 if no such |
480 |
jsr166 |
1.43 |
|
481 |
dl |
1.42 |
Itr(Object[] array) { |
482 |
|
|
lastRet = -1; |
483 |
|
|
this.array = array; |
484 |
dl |
1.2 |
} |
485 |
|
|
|
486 |
tim |
1.6 |
public boolean hasNext() { |
487 |
dl |
1.42 |
return cursor < array.length; |
488 |
tim |
1.6 |
} |
489 |
|
|
|
490 |
jsr166 |
1.49 |
@SuppressWarnings("unchecked") |
491 |
tim |
1.6 |
public E next() { |
492 |
dl |
1.42 |
if (cursor >= array.length) |
493 |
|
|
throw new NoSuchElementException(); |
494 |
|
|
lastRet = cursor; |
495 |
|
|
return (E)array[cursor++]; |
496 |
tim |
1.6 |
} |
497 |
|
|
|
498 |
|
|
public void remove() { |
499 |
jsr166 |
1.43 |
if (lastRet < 0) |
500 |
jsr166 |
1.49 |
throw new IllegalStateException(); |
501 |
dl |
1.42 |
Object x = array[lastRet]; |
502 |
|
|
lastRet = -1; |
503 |
|
|
// Traverse underlying queue to find == element, |
504 |
|
|
// not just a .equals element. |
505 |
dl |
1.2 |
lock.lock(); |
506 |
|
|
try { |
507 |
dl |
1.42 |
for (Iterator it = q.iterator(); it.hasNext(); ) { |
508 |
|
|
if (it.next() == x) { |
509 |
|
|
it.remove(); |
510 |
|
|
return; |
511 |
|
|
} |
512 |
|
|
} |
513 |
tim |
1.13 |
} finally { |
514 |
dl |
1.2 |
lock.unlock(); |
515 |
|
|
} |
516 |
tim |
1.6 |
} |
517 |
tim |
1.1 |
} |
518 |
|
|
|
519 |
|
|
} |