1 |
dl |
1.2 |
/* |
2 |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
dl |
1.33 |
* Expert Group and released to the public domain, as explained at |
4 |
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* http://creativecommons.org/licenses/publicdomain |
5 |
dl |
1.2 |
*/ |
6 |
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|
7 |
tim |
1.1 |
package java.util.concurrent; |
8 |
dl |
1.2 |
import java.util.concurrent.atomic.*; |
9 |
dl |
1.7 |
import java.util.concurrent.locks.*; |
10 |
tim |
1.1 |
import java.util.*; |
11 |
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|
12 |
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/** |
13 |
dholmes |
1.14 |
* An optionally-bounded {@linkplain BlockingQueue blocking queue} based on |
14 |
dholmes |
1.8 |
* linked nodes. |
15 |
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* This queue orders elements FIFO (first-in-first-out). |
16 |
tim |
1.12 |
* The <em>head</em> of the queue is that element that has been on the |
17 |
dholmes |
1.8 |
* queue the longest time. |
18 |
|
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* The <em>tail</em> of the queue is that element that has been on the |
19 |
dl |
1.20 |
* queue the shortest time. New elements |
20 |
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* are inserted at the tail of the queue, and the queue retrieval |
21 |
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* operations obtain elements at the head of the queue. |
22 |
dholmes |
1.8 |
* Linked queues typically have higher throughput than array-based queues but |
23 |
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* less predictable performance in most concurrent applications. |
24 |
tim |
1.12 |
* |
25 |
dl |
1.3 |
* <p> The optional capacity bound constructor argument serves as a |
26 |
dholmes |
1.8 |
* way to prevent excessive queue expansion. The capacity, if unspecified, |
27 |
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* is equal to {@link Integer#MAX_VALUE}. Linked nodes are |
28 |
dl |
1.3 |
* dynamically created upon each insertion unless this would bring the |
29 |
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* queue above capacity. |
30 |
dholmes |
1.8 |
* |
31 |
dl |
1.36 |
* <p>This class and its iterator implement all of the |
32 |
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* <em>optional</em> methods of the {@link Collection} and {@link |
33 |
dl |
1.38 |
* Iterator} interfaces. |
34 |
dl |
1.21 |
* |
35 |
dl |
1.34 |
* <p>This class is a member of the |
36 |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
37 |
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* Java Collections Framework</a>. |
38 |
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* |
39 |
dl |
1.6 |
* @since 1.5 |
40 |
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* @author Doug Lea |
41 |
dl |
1.27 |
* @param <E> the type of elements held in this collection |
42 |
tim |
1.12 |
* |
43 |
jsr166 |
1.40 |
*/ |
44 |
dl |
1.2 |
public class LinkedBlockingQueue<E> extends AbstractQueue<E> |
45 |
tim |
1.1 |
implements BlockingQueue<E>, java.io.Serializable { |
46 |
dl |
1.18 |
private static final long serialVersionUID = -6903933977591709194L; |
47 |
tim |
1.1 |
|
48 |
dl |
1.2 |
/* |
49 |
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* A variant of the "two lock queue" algorithm. The putLock gates |
50 |
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* entry to put (and offer), and has an associated condition for |
51 |
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* waiting puts. Similarly for the takeLock. The "count" field |
52 |
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* that they both rely on is maintained as an atomic to avoid |
53 |
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* needing to get both locks in most cases. Also, to minimize need |
54 |
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* for puts to get takeLock and vice-versa, cascading notifies are |
55 |
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* used. When a put notices that it has enabled at least one take, |
56 |
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* it signals taker. That taker in turn signals others if more |
57 |
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* items have been entered since the signal. And symmetrically for |
58 |
tim |
1.12 |
* takes signalling puts. Operations such as remove(Object) and |
59 |
dl |
1.2 |
* iterators acquire both locks. |
60 |
dl |
1.38 |
*/ |
61 |
dl |
1.2 |
|
62 |
dl |
1.6 |
/** |
63 |
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* Linked list node class |
64 |
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*/ |
65 |
dl |
1.2 |
static class Node<E> { |
66 |
dl |
1.6 |
/** The item, volatile to ensure barrier separating write and read */ |
67 |
dl |
1.2 |
volatile E item; |
68 |
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Node<E> next; |
69 |
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Node(E x) { item = x; } |
70 |
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} |
71 |
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|
72 |
dl |
1.6 |
/** The capacity bound, or Integer.MAX_VALUE if none */ |
73 |
dl |
1.2 |
private final int capacity; |
74 |
dl |
1.6 |
|
75 |
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/** Current number of elements */ |
76 |
dl |
1.19 |
private final AtomicInteger count = new AtomicInteger(0); |
77 |
dl |
1.2 |
|
78 |
dl |
1.6 |
/** Head of linked list */ |
79 |
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private transient Node<E> head; |
80 |
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|
81 |
dholmes |
1.8 |
/** Tail of linked list */ |
82 |
dl |
1.6 |
private transient Node<E> last; |
83 |
dl |
1.2 |
|
84 |
dl |
1.6 |
/** Lock held by take, poll, etc */ |
85 |
dl |
1.5 |
private final ReentrantLock takeLock = new ReentrantLock(); |
86 |
dl |
1.6 |
|
87 |
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/** Wait queue for waiting takes */ |
88 |
dl |
1.32 |
private final Condition notEmpty = takeLock.newCondition(); |
89 |
dl |
1.2 |
|
90 |
dl |
1.6 |
/** Lock held by put, offer, etc */ |
91 |
dl |
1.5 |
private final ReentrantLock putLock = new ReentrantLock(); |
92 |
dl |
1.6 |
|
93 |
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/** Wait queue for waiting puts */ |
94 |
dl |
1.32 |
private final Condition notFull = putLock.newCondition(); |
95 |
dl |
1.2 |
|
96 |
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/** |
97 |
jsr166 |
1.40 |
* Signals a waiting take. Called only from put/offer (which do not |
98 |
dl |
1.4 |
* otherwise ordinarily lock takeLock.) |
99 |
dl |
1.2 |
*/ |
100 |
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private void signalNotEmpty() { |
101 |
dl |
1.31 |
final ReentrantLock takeLock = this.takeLock; |
102 |
dl |
1.2 |
takeLock.lock(); |
103 |
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try { |
104 |
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notEmpty.signal(); |
105 |
tim |
1.17 |
} finally { |
106 |
dl |
1.2 |
takeLock.unlock(); |
107 |
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} |
108 |
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} |
109 |
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110 |
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/** |
111 |
jsr166 |
1.40 |
* Signals a waiting put. Called only from take/poll. |
112 |
dl |
1.2 |
*/ |
113 |
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private void signalNotFull() { |
114 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
115 |
dl |
1.2 |
putLock.lock(); |
116 |
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try { |
117 |
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notFull.signal(); |
118 |
tim |
1.17 |
} finally { |
119 |
dl |
1.2 |
putLock.unlock(); |
120 |
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} |
121 |
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} |
122 |
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123 |
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/** |
124 |
jsr166 |
1.40 |
* Creates a node and links it at end of queue. |
125 |
dl |
1.6 |
* @param x the item |
126 |
dl |
1.2 |
*/ |
127 |
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private void insert(E x) { |
128 |
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last = last.next = new Node<E>(x); |
129 |
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} |
130 |
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131 |
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/** |
132 |
jsr166 |
1.40 |
* Removes a node from head of queue, |
133 |
dl |
1.6 |
* @return the node |
134 |
dl |
1.2 |
*/ |
135 |
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private E extract() { |
136 |
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Node<E> first = head.next; |
137 |
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head = first; |
138 |
dl |
1.28 |
E x = first.item; |
139 |
dl |
1.2 |
first.item = null; |
140 |
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return x; |
141 |
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} |
142 |
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143 |
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/** |
144 |
tim |
1.12 |
* Lock to prevent both puts and takes. |
145 |
dl |
1.2 |
*/ |
146 |
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private void fullyLock() { |
147 |
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putLock.lock(); |
148 |
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takeLock.lock(); |
149 |
tim |
1.1 |
} |
150 |
dl |
1.2 |
|
151 |
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/** |
152 |
tim |
1.12 |
* Unlock to allow both puts and takes. |
153 |
dl |
1.2 |
*/ |
154 |
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private void fullyUnlock() { |
155 |
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takeLock.unlock(); |
156 |
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putLock.unlock(); |
157 |
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} |
158 |
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|
159 |
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|
160 |
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/** |
161 |
dholmes |
1.13 |
* Creates a <tt>LinkedBlockingQueue</tt> with a capacity of |
162 |
dholmes |
1.8 |
* {@link Integer#MAX_VALUE}. |
163 |
dl |
1.2 |
*/ |
164 |
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public LinkedBlockingQueue() { |
165 |
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this(Integer.MAX_VALUE); |
166 |
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} |
167 |
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|
168 |
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/** |
169 |
tim |
1.16 |
* Creates a <tt>LinkedBlockingQueue</tt> with the given (fixed) capacity. |
170 |
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* |
171 |
jsr166 |
1.43 |
* @param capacity the capacity of this queue |
172 |
dholmes |
1.8 |
* @throws IllegalArgumentException if <tt>capacity</tt> is not greater |
173 |
jsr166 |
1.43 |
* than zero |
174 |
dl |
1.2 |
*/ |
175 |
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public LinkedBlockingQueue(int capacity) { |
176 |
dholmes |
1.8 |
if (capacity <= 0) throw new IllegalArgumentException(); |
177 |
dl |
1.2 |
this.capacity = capacity; |
178 |
dl |
1.6 |
last = head = new Node<E>(null); |
179 |
dl |
1.2 |
} |
180 |
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|
181 |
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/** |
182 |
dholmes |
1.13 |
* Creates a <tt>LinkedBlockingQueue</tt> with a capacity of |
183 |
dholmes |
1.14 |
* {@link Integer#MAX_VALUE}, initially containing the elements of the |
184 |
tim |
1.12 |
* given collection, |
185 |
dholmes |
1.8 |
* added in traversal order of the collection's iterator. |
186 |
jsr166 |
1.43 |
* |
187 |
dholmes |
1.9 |
* @param c the collection of elements to initially contain |
188 |
jsr166 |
1.43 |
* @throws NullPointerException if the specified collection or any |
189 |
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* of its elements are null |
190 |
dl |
1.2 |
*/ |
191 |
dholmes |
1.10 |
public LinkedBlockingQueue(Collection<? extends E> c) { |
192 |
dl |
1.2 |
this(Integer.MAX_VALUE); |
193 |
dl |
1.38 |
for (E e : c) |
194 |
|
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add(e); |
195 |
dl |
1.2 |
} |
196 |
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|
197 |
dholmes |
1.9 |
|
198 |
dholmes |
1.8 |
// this doc comment is overridden to remove the reference to collections |
199 |
|
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// greater in size than Integer.MAX_VALUE |
200 |
tim |
1.12 |
/** |
201 |
dl |
1.20 |
* Returns the number of elements in this queue. |
202 |
|
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* |
203 |
jsr166 |
1.43 |
* @return the number of elements in this queue |
204 |
dholmes |
1.8 |
*/ |
205 |
dl |
1.2 |
public int size() { |
206 |
|
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return count.get(); |
207 |
tim |
1.1 |
} |
208 |
dl |
1.2 |
|
209 |
dholmes |
1.8 |
// this doc comment is a modified copy of the inherited doc comment, |
210 |
|
|
// without the reference to unlimited queues. |
211 |
tim |
1.12 |
/** |
212 |
jsr166 |
1.41 |
* Returns the number of additional elements that this queue can ideally |
213 |
|
|
* (in the absence of memory or resource constraints) accept without |
214 |
dholmes |
1.8 |
* blocking. This is always equal to the initial capacity of this queue |
215 |
|
|
* less the current <tt>size</tt> of this queue. |
216 |
jsr166 |
1.41 |
* |
217 |
|
|
* <p>Note that you <em>cannot</em> always tell if an attempt to insert |
218 |
|
|
* an element will succeed by inspecting <tt>remainingCapacity</tt> |
219 |
|
|
* because it may be the case that another thread is about to |
220 |
jsr166 |
1.43 |
* insert or remove an element. |
221 |
dholmes |
1.8 |
*/ |
222 |
dl |
1.2 |
public int remainingCapacity() { |
223 |
|
|
return capacity - count.get(); |
224 |
|
|
} |
225 |
|
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|
226 |
dholmes |
1.22 |
/** |
227 |
jsr166 |
1.44 |
* Inserts the specified element at the tail of this queue, waiting if |
228 |
dholmes |
1.22 |
* necessary for space to become available. |
229 |
jsr166 |
1.43 |
* |
230 |
|
|
* @throws InterruptedException {@inheritDoc} |
231 |
|
|
* @throws NullPointerException {@inheritDoc} |
232 |
dholmes |
1.22 |
*/ |
233 |
jsr166 |
1.42 |
public void put(E e) throws InterruptedException { |
234 |
|
|
if (e == null) throw new NullPointerException(); |
235 |
dl |
1.2 |
// Note: convention in all put/take/etc is to preset |
236 |
|
|
// local var holding count negative to indicate failure unless set. |
237 |
tim |
1.12 |
int c = -1; |
238 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
239 |
|
|
final AtomicInteger count = this.count; |
240 |
dl |
1.2 |
putLock.lockInterruptibly(); |
241 |
|
|
try { |
242 |
|
|
/* |
243 |
|
|
* Note that count is used in wait guard even though it is |
244 |
|
|
* not protected by lock. This works because count can |
245 |
|
|
* only decrease at this point (all other puts are shut |
246 |
|
|
* out by lock), and we (or some other waiting put) are |
247 |
|
|
* signalled if it ever changes from |
248 |
|
|
* capacity. Similarly for all other uses of count in |
249 |
|
|
* other wait guards. |
250 |
|
|
*/ |
251 |
|
|
try { |
252 |
tim |
1.12 |
while (count.get() == capacity) |
253 |
dl |
1.2 |
notFull.await(); |
254 |
tim |
1.17 |
} catch (InterruptedException ie) { |
255 |
dl |
1.2 |
notFull.signal(); // propagate to a non-interrupted thread |
256 |
|
|
throw ie; |
257 |
|
|
} |
258 |
jsr166 |
1.42 |
insert(e); |
259 |
dl |
1.2 |
c = count.getAndIncrement(); |
260 |
dl |
1.6 |
if (c + 1 < capacity) |
261 |
dl |
1.2 |
notFull.signal(); |
262 |
tim |
1.17 |
} finally { |
263 |
dl |
1.2 |
putLock.unlock(); |
264 |
|
|
} |
265 |
tim |
1.12 |
if (c == 0) |
266 |
dl |
1.2 |
signalNotEmpty(); |
267 |
tim |
1.1 |
} |
268 |
dl |
1.2 |
|
269 |
dholmes |
1.22 |
/** |
270 |
|
|
* Inserts the specified element at the tail of this queue, waiting if |
271 |
|
|
* necessary up to the specified wait time for space to become available. |
272 |
jsr166 |
1.43 |
* |
273 |
dl |
1.23 |
* @return <tt>true</tt> if successful, or <tt>false</tt> if |
274 |
jsr166 |
1.43 |
* the specified waiting time elapses before space is available. |
275 |
|
|
* @throws InterruptedException {@inheritDoc} |
276 |
|
|
* @throws NullPointerException {@inheritDoc} |
277 |
dholmes |
1.22 |
*/ |
278 |
jsr166 |
1.42 |
public boolean offer(E e, long timeout, TimeUnit unit) |
279 |
dholmes |
1.8 |
throws InterruptedException { |
280 |
tim |
1.12 |
|
281 |
jsr166 |
1.42 |
if (e == null) throw new NullPointerException(); |
282 |
dl |
1.2 |
long nanos = unit.toNanos(timeout); |
283 |
|
|
int c = -1; |
284 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
285 |
|
|
final AtomicInteger count = this.count; |
286 |
dholmes |
1.8 |
putLock.lockInterruptibly(); |
287 |
dl |
1.2 |
try { |
288 |
|
|
for (;;) { |
289 |
|
|
if (count.get() < capacity) { |
290 |
jsr166 |
1.42 |
insert(e); |
291 |
dl |
1.2 |
c = count.getAndIncrement(); |
292 |
dl |
1.6 |
if (c + 1 < capacity) |
293 |
dl |
1.2 |
notFull.signal(); |
294 |
|
|
break; |
295 |
|
|
} |
296 |
|
|
if (nanos <= 0) |
297 |
|
|
return false; |
298 |
|
|
try { |
299 |
|
|
nanos = notFull.awaitNanos(nanos); |
300 |
tim |
1.17 |
} catch (InterruptedException ie) { |
301 |
dl |
1.2 |
notFull.signal(); // propagate to a non-interrupted thread |
302 |
|
|
throw ie; |
303 |
|
|
} |
304 |
|
|
} |
305 |
tim |
1.17 |
} finally { |
306 |
dl |
1.2 |
putLock.unlock(); |
307 |
|
|
} |
308 |
tim |
1.12 |
if (c == 0) |
309 |
dl |
1.2 |
signalNotEmpty(); |
310 |
|
|
return true; |
311 |
tim |
1.1 |
} |
312 |
dl |
1.2 |
|
313 |
dl |
1.23 |
/** |
314 |
jsr166 |
1.44 |
* Inserts the specified element at the tail of this queue if it is |
315 |
|
|
* possible to do so immediately without exceeding the queue's capacity, |
316 |
|
|
* returning <tt>true</tt> upon success and <tt>false</tt> if this queue |
317 |
|
|
* is full. |
318 |
|
|
* When using a capacity-restricted queue, this method is generally |
319 |
|
|
* preferable to method {@link BlockingQueue#add add}, which can fail to |
320 |
|
|
* insert an element only by throwing an exception. |
321 |
dl |
1.23 |
* |
322 |
jsr166 |
1.43 |
* @throws NullPointerException if the specified element is null |
323 |
dl |
1.23 |
*/ |
324 |
jsr166 |
1.42 |
public boolean offer(E e) { |
325 |
|
|
if (e == null) throw new NullPointerException(); |
326 |
dl |
1.31 |
final AtomicInteger count = this.count; |
327 |
dl |
1.2 |
if (count.get() == capacity) |
328 |
|
|
return false; |
329 |
tim |
1.12 |
int c = -1; |
330 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
331 |
dholmes |
1.8 |
putLock.lock(); |
332 |
dl |
1.2 |
try { |
333 |
|
|
if (count.get() < capacity) { |
334 |
jsr166 |
1.42 |
insert(e); |
335 |
dl |
1.2 |
c = count.getAndIncrement(); |
336 |
dl |
1.6 |
if (c + 1 < capacity) |
337 |
dl |
1.2 |
notFull.signal(); |
338 |
|
|
} |
339 |
tim |
1.17 |
} finally { |
340 |
dl |
1.2 |
putLock.unlock(); |
341 |
|
|
} |
342 |
tim |
1.12 |
if (c == 0) |
343 |
dl |
1.2 |
signalNotEmpty(); |
344 |
|
|
return c >= 0; |
345 |
tim |
1.1 |
} |
346 |
dl |
1.2 |
|
347 |
|
|
|
348 |
|
|
public E take() throws InterruptedException { |
349 |
|
|
E x; |
350 |
|
|
int c = -1; |
351 |
dl |
1.31 |
final AtomicInteger count = this.count; |
352 |
|
|
final ReentrantLock takeLock = this.takeLock; |
353 |
dl |
1.2 |
takeLock.lockInterruptibly(); |
354 |
|
|
try { |
355 |
|
|
try { |
356 |
tim |
1.12 |
while (count.get() == 0) |
357 |
dl |
1.2 |
notEmpty.await(); |
358 |
tim |
1.17 |
} catch (InterruptedException ie) { |
359 |
dl |
1.2 |
notEmpty.signal(); // propagate to a non-interrupted thread |
360 |
|
|
throw ie; |
361 |
|
|
} |
362 |
|
|
|
363 |
|
|
x = extract(); |
364 |
|
|
c = count.getAndDecrement(); |
365 |
|
|
if (c > 1) |
366 |
|
|
notEmpty.signal(); |
367 |
tim |
1.17 |
} finally { |
368 |
dl |
1.2 |
takeLock.unlock(); |
369 |
|
|
} |
370 |
tim |
1.12 |
if (c == capacity) |
371 |
dl |
1.2 |
signalNotFull(); |
372 |
|
|
return x; |
373 |
|
|
} |
374 |
|
|
|
375 |
|
|
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
376 |
|
|
E x = null; |
377 |
|
|
int c = -1; |
378 |
dholmes |
1.8 |
long nanos = unit.toNanos(timeout); |
379 |
dl |
1.31 |
final AtomicInteger count = this.count; |
380 |
|
|
final ReentrantLock takeLock = this.takeLock; |
381 |
dl |
1.2 |
takeLock.lockInterruptibly(); |
382 |
|
|
try { |
383 |
|
|
for (;;) { |
384 |
|
|
if (count.get() > 0) { |
385 |
|
|
x = extract(); |
386 |
|
|
c = count.getAndDecrement(); |
387 |
|
|
if (c > 1) |
388 |
|
|
notEmpty.signal(); |
389 |
|
|
break; |
390 |
|
|
} |
391 |
|
|
if (nanos <= 0) |
392 |
|
|
return null; |
393 |
|
|
try { |
394 |
|
|
nanos = notEmpty.awaitNanos(nanos); |
395 |
tim |
1.17 |
} catch (InterruptedException ie) { |
396 |
dl |
1.2 |
notEmpty.signal(); // propagate to a non-interrupted thread |
397 |
|
|
throw ie; |
398 |
|
|
} |
399 |
|
|
} |
400 |
tim |
1.17 |
} finally { |
401 |
dl |
1.2 |
takeLock.unlock(); |
402 |
|
|
} |
403 |
tim |
1.12 |
if (c == capacity) |
404 |
dl |
1.2 |
signalNotFull(); |
405 |
|
|
return x; |
406 |
|
|
} |
407 |
|
|
|
408 |
|
|
public E poll() { |
409 |
dl |
1.31 |
final AtomicInteger count = this.count; |
410 |
dl |
1.2 |
if (count.get() == 0) |
411 |
|
|
return null; |
412 |
|
|
E x = null; |
413 |
tim |
1.12 |
int c = -1; |
414 |
dl |
1.31 |
final ReentrantLock takeLock = this.takeLock; |
415 |
dl |
1.30 |
takeLock.lock(); |
416 |
dl |
1.2 |
try { |
417 |
|
|
if (count.get() > 0) { |
418 |
|
|
x = extract(); |
419 |
|
|
c = count.getAndDecrement(); |
420 |
|
|
if (c > 1) |
421 |
|
|
notEmpty.signal(); |
422 |
|
|
} |
423 |
tim |
1.17 |
} finally { |
424 |
dl |
1.2 |
takeLock.unlock(); |
425 |
|
|
} |
426 |
tim |
1.12 |
if (c == capacity) |
427 |
dl |
1.2 |
signalNotFull(); |
428 |
|
|
return x; |
429 |
tim |
1.1 |
} |
430 |
dl |
1.2 |
|
431 |
|
|
|
432 |
|
|
public E peek() { |
433 |
|
|
if (count.get() == 0) |
434 |
|
|
return null; |
435 |
dl |
1.31 |
final ReentrantLock takeLock = this.takeLock; |
436 |
dholmes |
1.8 |
takeLock.lock(); |
437 |
dl |
1.2 |
try { |
438 |
|
|
Node<E> first = head.next; |
439 |
|
|
if (first == null) |
440 |
|
|
return null; |
441 |
|
|
else |
442 |
|
|
return first.item; |
443 |
tim |
1.17 |
} finally { |
444 |
dl |
1.2 |
takeLock.unlock(); |
445 |
|
|
} |
446 |
tim |
1.1 |
} |
447 |
|
|
|
448 |
dl |
1.35 |
/** |
449 |
jsr166 |
1.44 |
* Removes a single instance of the specified element from this queue, |
450 |
|
|
* if it is present. More formally, removes an element <tt>e</tt> such |
451 |
|
|
* that <tt>o.equals(e)</tt>, if this queue contains one or more such |
452 |
|
|
* elements. |
453 |
|
|
* Returns <tt>true</tt> if this queue contained the specified element |
454 |
|
|
* (or equivalently, if this queue changed as a result of the call). |
455 |
|
|
* |
456 |
|
|
* @param o element to be removed from this queue, if present |
457 |
|
|
* @return <tt>true</tt> if this queue changed as a result of the call |
458 |
dl |
1.35 |
*/ |
459 |
dholmes |
1.9 |
public boolean remove(Object o) { |
460 |
|
|
if (o == null) return false; |
461 |
dl |
1.2 |
boolean removed = false; |
462 |
|
|
fullyLock(); |
463 |
|
|
try { |
464 |
|
|
Node<E> trail = head; |
465 |
|
|
Node<E> p = head.next; |
466 |
|
|
while (p != null) { |
467 |
dholmes |
1.9 |
if (o.equals(p.item)) { |
468 |
dl |
1.2 |
removed = true; |
469 |
|
|
break; |
470 |
|
|
} |
471 |
|
|
trail = p; |
472 |
|
|
p = p.next; |
473 |
|
|
} |
474 |
|
|
if (removed) { |
475 |
|
|
p.item = null; |
476 |
|
|
trail.next = p.next; |
477 |
dl |
1.39 |
if (last == p) |
478 |
|
|
last = trail; |
479 |
dl |
1.2 |
if (count.getAndDecrement() == capacity) |
480 |
|
|
notFull.signalAll(); |
481 |
|
|
} |
482 |
tim |
1.17 |
} finally { |
483 |
dl |
1.2 |
fullyUnlock(); |
484 |
|
|
} |
485 |
|
|
return removed; |
486 |
tim |
1.1 |
} |
487 |
dl |
1.2 |
|
488 |
jsr166 |
1.43 |
/** |
489 |
|
|
* Returns an array containing all of the elements in this queue, in |
490 |
|
|
* proper sequence. |
491 |
|
|
* |
492 |
|
|
* <p>The returned array will be "safe" in that no references to it are |
493 |
|
|
* maintained by this queue. (In other words, this method must allocate |
494 |
|
|
* a new array). The caller is thus free to modify the returned array. |
495 |
|
|
* |
496 |
|
|
* <p>This method acts as bridge between array-based and collection-based |
497 |
|
|
* APIs. |
498 |
|
|
* |
499 |
|
|
* @return an array containing all of the elements in this queue |
500 |
|
|
*/ |
501 |
dl |
1.2 |
public Object[] toArray() { |
502 |
|
|
fullyLock(); |
503 |
|
|
try { |
504 |
|
|
int size = count.get(); |
505 |
tim |
1.12 |
Object[] a = new Object[size]; |
506 |
dl |
1.2 |
int k = 0; |
507 |
tim |
1.12 |
for (Node<E> p = head.next; p != null; p = p.next) |
508 |
dl |
1.2 |
a[k++] = p.item; |
509 |
|
|
return a; |
510 |
tim |
1.17 |
} finally { |
511 |
dl |
1.2 |
fullyUnlock(); |
512 |
|
|
} |
513 |
tim |
1.1 |
} |
514 |
dl |
1.2 |
|
515 |
jsr166 |
1.43 |
/** |
516 |
|
|
* Returns an array containing all of the elements in this queue, in |
517 |
|
|
* proper sequence; the runtime type of the returned array is that of |
518 |
|
|
* the specified array. If the queue fits in the specified array, it |
519 |
|
|
* is returned therein. Otherwise, a new array is allocated with the |
520 |
|
|
* runtime type of the specified array and the size of this queue. |
521 |
|
|
* |
522 |
|
|
* <p>If this queue fits in the specified array with room to spare |
523 |
|
|
* (i.e., the array has more elements than this queue), the element in |
524 |
|
|
* the array immediately following the end of the queue is set to |
525 |
|
|
* <tt>null</tt>. |
526 |
|
|
* |
527 |
|
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
528 |
|
|
* array-based and collection-based APIs. Further, this method allows |
529 |
|
|
* precise control over the runtime type of the output array, and may, |
530 |
|
|
* under certain circumstances, be used to save allocation costs. |
531 |
|
|
* |
532 |
|
|
* <p>Suppose <tt>x</tt> is a queue known to contain only strings. |
533 |
|
|
* The following code can be used to dump the queue into a newly |
534 |
|
|
* allocated array of <tt>String</tt>: |
535 |
|
|
* |
536 |
|
|
* <pre> |
537 |
|
|
* String[] y = x.toArray(new String[0]);</pre> |
538 |
|
|
* |
539 |
|
|
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
540 |
|
|
* <tt>toArray()</tt>. |
541 |
|
|
* |
542 |
|
|
* @param a the array into which the elements of the queue are to |
543 |
|
|
* be stored, if it is big enough; otherwise, a new array of the |
544 |
|
|
* same runtime type is allocated for this purpose |
545 |
|
|
* @return an array containing all of the elements in this queue |
546 |
|
|
* @throws ArrayStoreException if the runtime type of the specified array |
547 |
|
|
* is not a supertype of the runtime type of every element in |
548 |
|
|
* this queue |
549 |
|
|
* @throws NullPointerException if the specified array is null |
550 |
|
|
*/ |
551 |
dl |
1.2 |
public <T> T[] toArray(T[] a) { |
552 |
|
|
fullyLock(); |
553 |
|
|
try { |
554 |
|
|
int size = count.get(); |
555 |
|
|
if (a.length < size) |
556 |
dl |
1.4 |
a = (T[])java.lang.reflect.Array.newInstance |
557 |
|
|
(a.getClass().getComponentType(), size); |
558 |
tim |
1.12 |
|
559 |
dl |
1.2 |
int k = 0; |
560 |
tim |
1.12 |
for (Node p = head.next; p != null; p = p.next) |
561 |
dl |
1.2 |
a[k++] = (T)p.item; |
562 |
|
|
return a; |
563 |
tim |
1.17 |
} finally { |
564 |
dl |
1.2 |
fullyUnlock(); |
565 |
|
|
} |
566 |
tim |
1.1 |
} |
567 |
dl |
1.2 |
|
568 |
|
|
public String toString() { |
569 |
|
|
fullyLock(); |
570 |
|
|
try { |
571 |
|
|
return super.toString(); |
572 |
tim |
1.17 |
} finally { |
573 |
dl |
1.2 |
fullyUnlock(); |
574 |
|
|
} |
575 |
tim |
1.1 |
} |
576 |
dl |
1.2 |
|
577 |
dl |
1.35 |
/** |
578 |
|
|
* Atomically removes all of the elements from this queue. |
579 |
|
|
* The queue will be empty after this call returns. |
580 |
|
|
*/ |
581 |
dl |
1.24 |
public void clear() { |
582 |
|
|
fullyLock(); |
583 |
|
|
try { |
584 |
|
|
head.next = null; |
585 |
dl |
1.38 |
assert head.item == null; |
586 |
|
|
last = head; |
587 |
dl |
1.24 |
if (count.getAndSet(0) == capacity) |
588 |
|
|
notFull.signalAll(); |
589 |
|
|
} finally { |
590 |
|
|
fullyUnlock(); |
591 |
|
|
} |
592 |
|
|
} |
593 |
|
|
|
594 |
jsr166 |
1.43 |
/** |
595 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
596 |
|
|
* @throws ClassCastException {@inheritDoc} |
597 |
|
|
* @throws NullPointerException {@inheritDoc} |
598 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
599 |
|
|
*/ |
600 |
dl |
1.24 |
public int drainTo(Collection<? super E> c) { |
601 |
|
|
if (c == null) |
602 |
|
|
throw new NullPointerException(); |
603 |
|
|
if (c == this) |
604 |
|
|
throw new IllegalArgumentException(); |
605 |
|
|
Node first; |
606 |
|
|
fullyLock(); |
607 |
|
|
try { |
608 |
|
|
first = head.next; |
609 |
|
|
head.next = null; |
610 |
dl |
1.38 |
assert head.item == null; |
611 |
|
|
last = head; |
612 |
dl |
1.24 |
if (count.getAndSet(0) == capacity) |
613 |
|
|
notFull.signalAll(); |
614 |
|
|
} finally { |
615 |
|
|
fullyUnlock(); |
616 |
|
|
} |
617 |
|
|
// Transfer the elements outside of locks |
618 |
|
|
int n = 0; |
619 |
dl |
1.29 |
for (Node<E> p = first; p != null; p = p.next) { |
620 |
|
|
c.add(p.item); |
621 |
dl |
1.24 |
p.item = null; |
622 |
|
|
++n; |
623 |
|
|
} |
624 |
|
|
return n; |
625 |
|
|
} |
626 |
jsr166 |
1.40 |
|
627 |
jsr166 |
1.43 |
/** |
628 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
629 |
|
|
* @throws ClassCastException {@inheritDoc} |
630 |
|
|
* @throws NullPointerException {@inheritDoc} |
631 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
632 |
|
|
*/ |
633 |
dl |
1.24 |
public int drainTo(Collection<? super E> c, int maxElements) { |
634 |
|
|
if (c == null) |
635 |
|
|
throw new NullPointerException(); |
636 |
|
|
if (c == this) |
637 |
|
|
throw new IllegalArgumentException(); |
638 |
|
|
fullyLock(); |
639 |
|
|
try { |
640 |
|
|
int n = 0; |
641 |
dl |
1.29 |
Node<E> p = head.next; |
642 |
dl |
1.24 |
while (p != null && n < maxElements) { |
643 |
dl |
1.29 |
c.add(p.item); |
644 |
dl |
1.24 |
p.item = null; |
645 |
|
|
p = p.next; |
646 |
|
|
++n; |
647 |
|
|
} |
648 |
|
|
if (n != 0) { |
649 |
|
|
head.next = p; |
650 |
dl |
1.38 |
assert head.item == null; |
651 |
|
|
if (p == null) |
652 |
|
|
last = head; |
653 |
dl |
1.24 |
if (count.getAndAdd(-n) == capacity) |
654 |
|
|
notFull.signalAll(); |
655 |
|
|
} |
656 |
|
|
return n; |
657 |
|
|
} finally { |
658 |
|
|
fullyUnlock(); |
659 |
|
|
} |
660 |
|
|
} |
661 |
|
|
|
662 |
dholmes |
1.14 |
/** |
663 |
|
|
* Returns an iterator over the elements in this queue in proper sequence. |
664 |
dl |
1.15 |
* The returned <tt>Iterator</tt> is a "weakly consistent" iterator that |
665 |
jsr166 |
1.40 |
* will never throw {@link ConcurrentModificationException}, |
666 |
dl |
1.15 |
* and guarantees to traverse elements as they existed upon |
667 |
|
|
* construction of the iterator, and may (but is not guaranteed to) |
668 |
|
|
* reflect any modifications subsequent to construction. |
669 |
dholmes |
1.14 |
* |
670 |
jsr166 |
1.43 |
* @return an iterator over the elements in this queue in proper sequence |
671 |
dholmes |
1.14 |
*/ |
672 |
dl |
1.2 |
public Iterator<E> iterator() { |
673 |
|
|
return new Itr(); |
674 |
tim |
1.1 |
} |
675 |
dl |
1.2 |
|
676 |
|
|
private class Itr implements Iterator<E> { |
677 |
tim |
1.12 |
/* |
678 |
dl |
1.4 |
* Basic weak-consistent iterator. At all times hold the next |
679 |
|
|
* item to hand out so that if hasNext() reports true, we will |
680 |
|
|
* still have it to return even if lost race with a take etc. |
681 |
|
|
*/ |
682 |
dl |
1.31 |
private Node<E> current; |
683 |
|
|
private Node<E> lastRet; |
684 |
|
|
private E currentElement; |
685 |
tim |
1.12 |
|
686 |
dl |
1.2 |
Itr() { |
687 |
dl |
1.31 |
final ReentrantLock putLock = LinkedBlockingQueue.this.putLock; |
688 |
|
|
final ReentrantLock takeLock = LinkedBlockingQueue.this.takeLock; |
689 |
|
|
putLock.lock(); |
690 |
|
|
takeLock.lock(); |
691 |
dl |
1.2 |
try { |
692 |
|
|
current = head.next; |
693 |
dl |
1.4 |
if (current != null) |
694 |
|
|
currentElement = current.item; |
695 |
tim |
1.17 |
} finally { |
696 |
dl |
1.31 |
takeLock.unlock(); |
697 |
|
|
putLock.unlock(); |
698 |
dl |
1.2 |
} |
699 |
|
|
} |
700 |
tim |
1.12 |
|
701 |
|
|
public boolean hasNext() { |
702 |
dl |
1.2 |
return current != null; |
703 |
|
|
} |
704 |
|
|
|
705 |
tim |
1.12 |
public E next() { |
706 |
dl |
1.31 |
final ReentrantLock putLock = LinkedBlockingQueue.this.putLock; |
707 |
|
|
final ReentrantLock takeLock = LinkedBlockingQueue.this.takeLock; |
708 |
|
|
putLock.lock(); |
709 |
|
|
takeLock.lock(); |
710 |
dl |
1.2 |
try { |
711 |
|
|
if (current == null) |
712 |
|
|
throw new NoSuchElementException(); |
713 |
dl |
1.4 |
E x = currentElement; |
714 |
dl |
1.2 |
lastRet = current; |
715 |
|
|
current = current.next; |
716 |
dl |
1.4 |
if (current != null) |
717 |
|
|
currentElement = current.item; |
718 |
dl |
1.2 |
return x; |
719 |
tim |
1.17 |
} finally { |
720 |
dl |
1.31 |
takeLock.unlock(); |
721 |
|
|
putLock.unlock(); |
722 |
dl |
1.2 |
} |
723 |
|
|
} |
724 |
|
|
|
725 |
tim |
1.12 |
public void remove() { |
726 |
dl |
1.2 |
if (lastRet == null) |
727 |
tim |
1.12 |
throw new IllegalStateException(); |
728 |
dl |
1.31 |
final ReentrantLock putLock = LinkedBlockingQueue.this.putLock; |
729 |
|
|
final ReentrantLock takeLock = LinkedBlockingQueue.this.takeLock; |
730 |
|
|
putLock.lock(); |
731 |
|
|
takeLock.lock(); |
732 |
dl |
1.2 |
try { |
733 |
|
|
Node<E> node = lastRet; |
734 |
|
|
lastRet = null; |
735 |
|
|
Node<E> trail = head; |
736 |
|
|
Node<E> p = head.next; |
737 |
|
|
while (p != null && p != node) { |
738 |
|
|
trail = p; |
739 |
|
|
p = p.next; |
740 |
|
|
} |
741 |
|
|
if (p == node) { |
742 |
|
|
p.item = null; |
743 |
|
|
trail.next = p.next; |
744 |
dl |
1.39 |
if (last == p) |
745 |
|
|
last = trail; |
746 |
dl |
1.2 |
int c = count.getAndDecrement(); |
747 |
|
|
if (c == capacity) |
748 |
|
|
notFull.signalAll(); |
749 |
|
|
} |
750 |
tim |
1.17 |
} finally { |
751 |
dl |
1.31 |
takeLock.unlock(); |
752 |
|
|
putLock.unlock(); |
753 |
dl |
1.2 |
} |
754 |
|
|
} |
755 |
tim |
1.1 |
} |
756 |
dl |
1.2 |
|
757 |
|
|
/** |
758 |
|
|
* Save the state to a stream (that is, serialize it). |
759 |
|
|
* |
760 |
|
|
* @serialData The capacity is emitted (int), followed by all of |
761 |
|
|
* its elements (each an <tt>Object</tt>) in the proper order, |
762 |
|
|
* followed by a null |
763 |
dl |
1.6 |
* @param s the stream |
764 |
dl |
1.2 |
*/ |
765 |
|
|
private void writeObject(java.io.ObjectOutputStream s) |
766 |
|
|
throws java.io.IOException { |
767 |
|
|
|
768 |
tim |
1.12 |
fullyLock(); |
769 |
dl |
1.2 |
try { |
770 |
|
|
// Write out any hidden stuff, plus capacity |
771 |
|
|
s.defaultWriteObject(); |
772 |
|
|
|
773 |
|
|
// Write out all elements in the proper order. |
774 |
tim |
1.12 |
for (Node<E> p = head.next; p != null; p = p.next) |
775 |
dl |
1.2 |
s.writeObject(p.item); |
776 |
|
|
|
777 |
|
|
// Use trailing null as sentinel |
778 |
|
|
s.writeObject(null); |
779 |
tim |
1.17 |
} finally { |
780 |
dl |
1.2 |
fullyUnlock(); |
781 |
|
|
} |
782 |
tim |
1.1 |
} |
783 |
|
|
|
784 |
dl |
1.2 |
/** |
785 |
dholmes |
1.8 |
* Reconstitute this queue instance from a stream (that is, |
786 |
dl |
1.2 |
* deserialize it). |
787 |
dl |
1.6 |
* @param s the stream |
788 |
dl |
1.2 |
*/ |
789 |
|
|
private void readObject(java.io.ObjectInputStream s) |
790 |
|
|
throws java.io.IOException, ClassNotFoundException { |
791 |
tim |
1.12 |
// Read in capacity, and any hidden stuff |
792 |
|
|
s.defaultReadObject(); |
793 |
dl |
1.2 |
|
794 |
dl |
1.19 |
count.set(0); |
795 |
|
|
last = head = new Node<E>(null); |
796 |
|
|
|
797 |
dl |
1.6 |
// Read in all elements and place in queue |
798 |
dl |
1.2 |
for (;;) { |
799 |
|
|
E item = (E)s.readObject(); |
800 |
|
|
if (item == null) |
801 |
|
|
break; |
802 |
|
|
add(item); |
803 |
|
|
} |
804 |
tim |
1.1 |
} |
805 |
|
|
} |