1 |
dl |
1.2 |
/* |
2 |
|
|
* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
|
|
* Expert Group and released to the public domain. Use, modify, and |
4 |
|
|
* redistribute this code in any way without acknowledgement. |
5 |
|
|
*/ |
6 |
|
|
|
7 |
|
|
|
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 |
|
|
|
12 |
|
|
/** |
13 |
tim |
1.9 |
* An unbounded {@linkplain BlockingQueue blocking queue} of <tt>Delayed</tt> |
14 |
dholmes |
1.7 |
* elements, in which an element can only be taken when its delay has expired. |
15 |
|
|
* The <em>head</em> of the queue is that <tt>Delayed</tt> element whose delay |
16 |
|
|
* expired furthest in the past - if no delay has expired there is no head and |
17 |
|
|
* <tt>poll</tt> will return <tt>null</tt>. |
18 |
|
|
* This queue does not permit <tt>null</tt> elements. |
19 |
dl |
1.4 |
* @since 1.5 |
20 |
|
|
* @author Doug Lea |
21 |
|
|
*/ |
22 |
tim |
1.1 |
|
23 |
dl |
1.3 |
public class DelayQueue<E extends Delayed> extends AbstractQueue<E> |
24 |
|
|
implements BlockingQueue<E> { |
25 |
tim |
1.6 |
|
26 |
dl |
1.2 |
private transient final ReentrantLock lock = new ReentrantLock(); |
27 |
dl |
1.4 |
private transient final Condition available = lock.newCondition(); |
28 |
dl |
1.3 |
private final PriorityQueue<E> q = new PriorityQueue<E>(); |
29 |
tim |
1.1 |
|
30 |
dl |
1.4 |
/** |
31 |
dholmes |
1.7 |
* Creates a new <tt>DelayQueue</tt> that is initially empty. |
32 |
dl |
1.4 |
*/ |
33 |
tim |
1.1 |
public DelayQueue() {} |
34 |
|
|
|
35 |
tim |
1.6 |
/** |
36 |
tim |
1.9 |
* Creates a <tt>DelayQueue</tt> initially containing the elements of the |
37 |
dholmes |
1.7 |
* given collection of {@link Delayed} instances. |
38 |
|
|
* |
39 |
|
|
* @throws NullPointerException if <tt>c</tt> or any element within it |
40 |
|
|
* is <tt>null</tt> |
41 |
tim |
1.6 |
* |
42 |
|
|
*/ |
43 |
|
|
public DelayQueue(Collection<? extends E> c) { |
44 |
|
|
this.addAll(c); |
45 |
|
|
} |
46 |
|
|
|
47 |
dholmes |
1.7 |
/** |
48 |
|
|
* Add the specified element to this delay queue. |
49 |
|
|
* |
50 |
|
|
* @return <tt>true</tt> |
51 |
|
|
* @throws NullPointerException {@inheritDoc} |
52 |
|
|
*/ |
53 |
|
|
public boolean offer(E o) { |
54 |
dl |
1.2 |
lock.lock(); |
55 |
|
|
try { |
56 |
dl |
1.3 |
E first = q.peek(); |
57 |
dholmes |
1.7 |
q.offer(o); |
58 |
|
|
if (first == null || o.compareTo(first) < 0) |
59 |
dl |
1.4 |
available.signalAll(); |
60 |
dl |
1.2 |
return true; |
61 |
|
|
} |
62 |
|
|
finally { |
63 |
|
|
lock.unlock(); |
64 |
|
|
} |
65 |
|
|
} |
66 |
|
|
|
67 |
dholmes |
1.7 |
|
68 |
|
|
/** |
69 |
|
|
* Adds the specified element to this delay queue. As the queue is |
70 |
|
|
* unbounded this method will never block. |
71 |
|
|
* @throws NullPointerException {@inheritDoc} |
72 |
|
|
*/ |
73 |
|
|
public void put(E o) { |
74 |
|
|
offer(o); |
75 |
dl |
1.2 |
} |
76 |
|
|
|
77 |
dholmes |
1.7 |
/** |
78 |
|
|
* Adds the specified element to this priority queue. As the queue is |
79 |
|
|
* unbounded this method will never block. |
80 |
|
|
* @param o {@inheritDoc} |
81 |
tim |
1.11 |
* @param time This parameter is ignored as the method never blocks |
82 |
dholmes |
1.7 |
* @param unit This parameter is ignored as the method never blocks |
83 |
|
|
* @throws NullPointerException {@inheritDoc} |
84 |
|
|
* @return <tt>true</tt> |
85 |
|
|
*/ |
86 |
|
|
public boolean offer(E o, long time, TimeUnit unit) { |
87 |
|
|
return offer(o); |
88 |
dl |
1.2 |
} |
89 |
|
|
|
90 |
dholmes |
1.7 |
/** |
91 |
|
|
* Adds the specified element to this queue. |
92 |
|
|
* @return <tt>true</tt> (as per the general contract of |
93 |
|
|
* <tt>Collection.add</tt>). |
94 |
|
|
* |
95 |
|
|
* @throws NullPointerException {@inheritDoc} |
96 |
|
|
*/ |
97 |
|
|
public boolean add(E o) { |
98 |
|
|
return offer(o); |
99 |
dl |
1.2 |
} |
100 |
|
|
|
101 |
dl |
1.3 |
public E take() throws InterruptedException { |
102 |
dl |
1.2 |
lock.lockInterruptibly(); |
103 |
|
|
try { |
104 |
|
|
for (;;) { |
105 |
dl |
1.3 |
E first = q.peek(); |
106 |
dl |
1.12 |
if (first == null) { |
107 |
dl |
1.4 |
available.await(); |
108 |
dl |
1.12 |
} |
109 |
dl |
1.2 |
else { |
110 |
|
|
long delay = first.getDelay(TimeUnit.NANOSECONDS); |
111 |
dl |
1.12 |
if (delay > 0) { |
112 |
|
|
long tl = available.awaitNanos(delay); |
113 |
|
|
} |
114 |
dl |
1.2 |
else { |
115 |
dl |
1.3 |
E x = q.poll(); |
116 |
dl |
1.2 |
assert x != null; |
117 |
|
|
if (q.size() != 0) |
118 |
dl |
1.4 |
available.signalAll(); // wake up other takers |
119 |
dl |
1.2 |
return x; |
120 |
tim |
1.6 |
|
121 |
dl |
1.2 |
} |
122 |
|
|
} |
123 |
|
|
} |
124 |
|
|
} |
125 |
|
|
finally { |
126 |
|
|
lock.unlock(); |
127 |
|
|
} |
128 |
|
|
} |
129 |
|
|
|
130 |
dl |
1.3 |
public E poll(long time, TimeUnit unit) throws InterruptedException { |
131 |
dl |
1.2 |
lock.lockInterruptibly(); |
132 |
|
|
long nanos = unit.toNanos(time); |
133 |
|
|
try { |
134 |
|
|
for (;;) { |
135 |
dl |
1.3 |
E first = q.peek(); |
136 |
dl |
1.2 |
if (first == null) { |
137 |
|
|
if (nanos <= 0) |
138 |
|
|
return null; |
139 |
|
|
else |
140 |
dl |
1.4 |
nanos = available.awaitNanos(nanos); |
141 |
dl |
1.2 |
} |
142 |
|
|
else { |
143 |
|
|
long delay = first.getDelay(TimeUnit.NANOSECONDS); |
144 |
|
|
if (delay > 0) { |
145 |
|
|
if (delay > nanos) |
146 |
|
|
delay = nanos; |
147 |
dl |
1.4 |
long timeLeft = available.awaitNanos(delay); |
148 |
dl |
1.2 |
nanos -= delay - timeLeft; |
149 |
|
|
} |
150 |
|
|
else { |
151 |
dl |
1.3 |
E x = q.poll(); |
152 |
dl |
1.2 |
assert x != null; |
153 |
|
|
if (q.size() != 0) |
154 |
tim |
1.6 |
available.signalAll(); |
155 |
dl |
1.2 |
return x; |
156 |
|
|
} |
157 |
|
|
} |
158 |
|
|
} |
159 |
|
|
} |
160 |
|
|
finally { |
161 |
|
|
lock.unlock(); |
162 |
|
|
} |
163 |
|
|
} |
164 |
|
|
|
165 |
|
|
|
166 |
dl |
1.3 |
public E poll() { |
167 |
dl |
1.2 |
lock.lock(); |
168 |
|
|
try { |
169 |
dl |
1.3 |
E first = q.peek(); |
170 |
dl |
1.2 |
if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0) |
171 |
|
|
return null; |
172 |
|
|
else { |
173 |
dl |
1.3 |
E x = q.poll(); |
174 |
dl |
1.2 |
assert x != null; |
175 |
|
|
if (q.size() != 0) |
176 |
tim |
1.6 |
available.signalAll(); |
177 |
dl |
1.2 |
return x; |
178 |
|
|
} |
179 |
|
|
} |
180 |
|
|
finally { |
181 |
|
|
lock.unlock(); |
182 |
|
|
} |
183 |
|
|
} |
184 |
|
|
|
185 |
dl |
1.3 |
public E peek() { |
186 |
dl |
1.2 |
lock.lock(); |
187 |
|
|
try { |
188 |
|
|
return q.peek(); |
189 |
|
|
} |
190 |
|
|
finally { |
191 |
|
|
lock.unlock(); |
192 |
|
|
} |
193 |
tim |
1.1 |
} |
194 |
|
|
|
195 |
dl |
1.2 |
public int size() { |
196 |
|
|
lock.lock(); |
197 |
|
|
try { |
198 |
|
|
return q.size(); |
199 |
|
|
} |
200 |
|
|
finally { |
201 |
|
|
lock.unlock(); |
202 |
|
|
} |
203 |
|
|
} |
204 |
|
|
|
205 |
dholmes |
1.7 |
/** |
206 |
|
|
* Atomically removes all of the elements from this delay queue. |
207 |
|
|
* The queue will be empty after this call returns. |
208 |
|
|
*/ |
209 |
dl |
1.2 |
public void clear() { |
210 |
|
|
lock.lock(); |
211 |
|
|
try { |
212 |
|
|
q.clear(); |
213 |
|
|
} |
214 |
|
|
finally { |
215 |
|
|
lock.unlock(); |
216 |
|
|
} |
217 |
|
|
} |
218 |
tim |
1.1 |
|
219 |
dholmes |
1.7 |
/** |
220 |
|
|
* Always returns <tt>Integer.MAX_VALUE</tt> because |
221 |
|
|
* a <tt>DelayQueue</tt> is not capacity constrained. |
222 |
|
|
* @return <tt>Integer.MAX_VALUE</tt> |
223 |
|
|
*/ |
224 |
dl |
1.2 |
public int remainingCapacity() { |
225 |
|
|
return Integer.MAX_VALUE; |
226 |
tim |
1.1 |
} |
227 |
dl |
1.2 |
|
228 |
|
|
public Object[] toArray() { |
229 |
|
|
lock.lock(); |
230 |
|
|
try { |
231 |
|
|
return q.toArray(); |
232 |
|
|
} |
233 |
|
|
finally { |
234 |
|
|
lock.unlock(); |
235 |
|
|
} |
236 |
tim |
1.1 |
} |
237 |
dl |
1.2 |
|
238 |
|
|
public <T> T[] toArray(T[] array) { |
239 |
|
|
lock.lock(); |
240 |
|
|
try { |
241 |
|
|
return q.toArray(array); |
242 |
|
|
} |
243 |
|
|
finally { |
244 |
|
|
lock.unlock(); |
245 |
|
|
} |
246 |
tim |
1.1 |
} |
247 |
|
|
|
248 |
dholmes |
1.7 |
/** |
249 |
|
|
* Removes a single instance of the specified element from this |
250 |
|
|
* queue, if it is present. More formally, |
251 |
|
|
* removes an element <tt>e</tt> such that <tt>(o==null ? e==null : |
252 |
|
|
* o.equals(e))</tt>, if the queue contains one or more such |
253 |
|
|
* elements. Returns <tt>true</tt> if the queue contained the |
254 |
|
|
* specified element (or equivalently, if the queue changed as a |
255 |
|
|
* result of the call). |
256 |
|
|
* |
257 |
|
|
* <p>This implementation iterates over the queue looking for the |
258 |
|
|
* specified element. If it finds the element, it removes the element |
259 |
|
|
* from the queue using the iterator's remove method.<p> |
260 |
|
|
* |
261 |
|
|
*/ |
262 |
|
|
public boolean remove(Object o) { |
263 |
dl |
1.2 |
lock.lock(); |
264 |
|
|
try { |
265 |
dholmes |
1.7 |
return q.remove(o); |
266 |
dl |
1.2 |
} |
267 |
|
|
finally { |
268 |
|
|
lock.unlock(); |
269 |
|
|
} |
270 |
|
|
} |
271 |
|
|
|
272 |
dholmes |
1.7 |
/** |
273 |
|
|
* Returns an iterator over the elements in this queue. The iterator |
274 |
dl |
1.8 |
* does not return the elements in any particular order. The |
275 |
|
|
* returned iterator is a "fast-fail" iterator that will |
276 |
|
|
* throw {@link java.util.ConcurrentModificationException} |
277 |
|
|
* upon detected interference. |
278 |
dholmes |
1.7 |
* |
279 |
|
|
* @return an iterator over the elements in this queue. |
280 |
|
|
*/ |
281 |
dl |
1.3 |
public Iterator<E> iterator() { |
282 |
dl |
1.2 |
lock.lock(); |
283 |
|
|
try { |
284 |
|
|
return new Itr(q.iterator()); |
285 |
|
|
} |
286 |
|
|
finally { |
287 |
|
|
lock.unlock(); |
288 |
|
|
} |
289 |
|
|
} |
290 |
|
|
|
291 |
dl |
1.3 |
private class Itr<E> implements Iterator<E> { |
292 |
|
|
private final Iterator<E> iter; |
293 |
tim |
1.6 |
Itr(Iterator<E> i) { |
294 |
|
|
iter = i; |
295 |
dl |
1.2 |
} |
296 |
|
|
|
297 |
tim |
1.6 |
public boolean hasNext() { |
298 |
dl |
1.2 |
return iter.hasNext(); |
299 |
tim |
1.6 |
} |
300 |
|
|
|
301 |
|
|
public E next() { |
302 |
dl |
1.2 |
lock.lock(); |
303 |
|
|
try { |
304 |
|
|
return iter.next(); |
305 |
|
|
} |
306 |
|
|
finally { |
307 |
|
|
lock.unlock(); |
308 |
|
|
} |
309 |
tim |
1.6 |
} |
310 |
|
|
|
311 |
|
|
public void remove() { |
312 |
dl |
1.2 |
lock.lock(); |
313 |
|
|
try { |
314 |
|
|
iter.remove(); |
315 |
|
|
} |
316 |
|
|
finally { |
317 |
|
|
lock.unlock(); |
318 |
|
|
} |
319 |
tim |
1.6 |
} |
320 |
tim |
1.1 |
} |
321 |
|
|
|
322 |
|
|
} |