1 |
dl |
1.2 |
/* |
2 |
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* 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 |
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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 |
1.11 |
import java.util.concurrent.locks.*; |
9 |
tim |
1.1 |
import java.util.*; |
10 |
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|
11 |
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/** |
12 |
dl |
1.25 |
* A bounded {@linkplain BlockingQueue blocking queue} backed by an |
13 |
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* array. This queue orders elements FIFO (first-in-first-out). The |
14 |
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* <em>head</em> of the queue is that element that has been on the |
15 |
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* queue the longest time. The <em>tail</em> of the queue is that |
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* element that has been on the queue the shortest time. New elements |
17 |
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* are inserted at the tail of the queue, and the queue retrieval |
18 |
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* 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 |
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* fixed-sized array holds elements inserted by producers and |
22 |
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* extracted by consumers. Once created, the capacity cannot be |
23 |
jsr166 |
1.50 |
* increased. Attempts to <tt>put</tt> an element into a full queue |
24 |
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* will result in the operation blocking; attempts to <tt>take</tt> an |
25 |
dl |
1.40 |
* element from an empty queue will similarly block. |
26 |
dl |
1.11 |
* |
27 |
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* <p> This class supports an optional fairness policy for ordering |
28 |
dl |
1.42 |
* waiting producer and consumer threads. By default, this ordering |
29 |
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* is not guaranteed. However, a queue constructed with fairness set |
30 |
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* to <tt>true</tt> grants threads access in FIFO order. Fairness |
31 |
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* generally decreases throughput but reduces variability and avoids |
32 |
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* starvation. |
33 |
brian |
1.7 |
* |
34 |
dl |
1.43 |
* <p>This class and its iterator implement all of the |
35 |
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* <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 |
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* |
42 |
dl |
1.8 |
* @since 1.5 |
43 |
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* @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 |
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|
49 |
dl |
1.36 |
/** |
50 |
dl |
1.42 |
* Serialization ID. This class relies on default serialization |
51 |
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* even for the items array, which is default-serialized, even if |
52 |
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* it is empty. Otherwise it could not be declared final, which is |
53 |
dl |
1.36 |
* necessary here. |
54 |
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*/ |
55 |
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private static final long serialVersionUID = -817911632652898426L; |
56 |
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57 |
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/** The queued items */ |
58 |
jsr166 |
1.58 |
final E[] items; |
59 |
dl |
1.8 |
/** items index for next take, poll or remove */ |
60 |
jsr166 |
1.58 |
int takeIndex; |
61 |
dl |
1.8 |
/** items index for next put, offer, or add. */ |
62 |
jsr166 |
1.58 |
int putIndex; |
63 |
dl |
1.8 |
/** Number of items in the queue */ |
64 |
jsr166 |
1.59 |
int count; |
65 |
tim |
1.12 |
|
66 |
dl |
1.5 |
/* |
67 |
dl |
1.36 |
* Concurrency control uses the classic two-condition algorithm |
68 |
dl |
1.5 |
* found in any textbook. |
69 |
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*/ |
70 |
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|
71 |
dl |
1.11 |
/** Main lock guarding all access */ |
72 |
jsr166 |
1.58 |
final ReentrantLock lock; |
73 |
dholmes |
1.13 |
/** Condition for waiting takes */ |
74 |
dl |
1.37 |
private final Condition notEmpty; |
75 |
dl |
1.35 |
/** Condition for waiting puts */ |
76 |
dl |
1.37 |
private final Condition notFull; |
77 |
dl |
1.5 |
|
78 |
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// Internal helper methods |
79 |
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80 |
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/** |
81 |
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* Circularly increment i. |
82 |
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*/ |
83 |
dl |
1.40 |
final int inc(int i) { |
84 |
jsr166 |
1.58 |
return (++i == items.length) ? 0 : i; |
85 |
dl |
1.5 |
} |
86 |
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87 |
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/** |
88 |
jsr166 |
1.47 |
* Inserts element at current put position, advances, and signals. |
89 |
dl |
1.9 |
* Call only when holding lock. |
90 |
dl |
1.5 |
*/ |
91 |
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private void insert(E x) { |
92 |
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items[putIndex] = x; |
93 |
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putIndex = inc(putIndex); |
94 |
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++count; |
95 |
dl |
1.9 |
notEmpty.signal(); |
96 |
tim |
1.1 |
} |
97 |
tim |
1.12 |
|
98 |
dl |
1.5 |
/** |
99 |
jsr166 |
1.47 |
* Extracts element at current take position, advances, and signals. |
100 |
dl |
1.9 |
* Call only when holding lock. |
101 |
dl |
1.5 |
*/ |
102 |
dholmes |
1.13 |
private E extract() { |
103 |
dl |
1.36 |
final E[] items = this.items; |
104 |
dl |
1.5 |
E x = items[takeIndex]; |
105 |
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items[takeIndex] = null; |
106 |
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takeIndex = inc(takeIndex); |
107 |
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--count; |
108 |
dl |
1.9 |
notFull.signal(); |
109 |
dl |
1.5 |
return x; |
110 |
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} |
111 |
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112 |
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/** |
113 |
tim |
1.12 |
* Utility for remove and iterator.remove: Delete item at position i. |
114 |
dl |
1.9 |
* Call only when holding lock. |
115 |
dl |
1.5 |
*/ |
116 |
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void removeAt(int i) { |
117 |
dl |
1.36 |
final E[] items = this.items; |
118 |
dl |
1.9 |
// if removing front item, just advance |
119 |
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if (i == takeIndex) { |
120 |
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items[takeIndex] = null; |
121 |
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takeIndex = inc(takeIndex); |
122 |
tim |
1.23 |
} else { |
123 |
dl |
1.9 |
// slide over all others up through putIndex. |
124 |
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for (;;) { |
125 |
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int nexti = inc(i); |
126 |
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if (nexti != putIndex) { |
127 |
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items[i] = items[nexti]; |
128 |
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i = nexti; |
129 |
tim |
1.23 |
} else { |
130 |
dl |
1.9 |
items[i] = null; |
131 |
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putIndex = i; |
132 |
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break; |
133 |
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} |
134 |
dl |
1.5 |
} |
135 |
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} |
136 |
dl |
1.9 |
--count; |
137 |
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notFull.signal(); |
138 |
tim |
1.1 |
} |
139 |
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140 |
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/** |
141 |
dholmes |
1.21 |
* Creates an <tt>ArrayBlockingQueue</tt> with the given (fixed) |
142 |
dholmes |
1.13 |
* capacity and default access policy. |
143 |
jsr166 |
1.50 |
* |
144 |
dholmes |
1.13 |
* @param capacity the capacity of this queue |
145 |
dholmes |
1.16 |
* @throws IllegalArgumentException if <tt>capacity</tt> is less than 1 |
146 |
dl |
1.5 |
*/ |
147 |
dholmes |
1.13 |
public ArrayBlockingQueue(int capacity) { |
148 |
dl |
1.36 |
this(capacity, false); |
149 |
dl |
1.5 |
} |
150 |
dl |
1.2 |
|
151 |
dl |
1.5 |
/** |
152 |
dholmes |
1.21 |
* Creates an <tt>ArrayBlockingQueue</tt> with the given (fixed) |
153 |
dholmes |
1.13 |
* capacity and the specified access policy. |
154 |
jsr166 |
1.50 |
* |
155 |
dholmes |
1.13 |
* @param capacity the capacity of this queue |
156 |
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* @param fair if <tt>true</tt> then queue accesses for threads blocked |
157 |
jsr166 |
1.50 |
* on insertion or removal, are processed in FIFO order; |
158 |
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* if <tt>false</tt> the access order is unspecified. |
159 |
dholmes |
1.16 |
* @throws IllegalArgumentException if <tt>capacity</tt> is less than 1 |
160 |
dl |
1.11 |
*/ |
161 |
dholmes |
1.13 |
public ArrayBlockingQueue(int capacity, boolean fair) { |
162 |
dl |
1.36 |
if (capacity <= 0) |
163 |
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throw new IllegalArgumentException(); |
164 |
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this.items = (E[]) new Object[capacity]; |
165 |
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lock = new ReentrantLock(fair); |
166 |
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notEmpty = lock.newCondition(); |
167 |
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notFull = lock.newCondition(); |
168 |
dl |
1.5 |
} |
169 |
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|
170 |
dholmes |
1.16 |
/** |
171 |
dholmes |
1.21 |
* Creates an <tt>ArrayBlockingQueue</tt> with the given (fixed) |
172 |
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* capacity, the specified access policy and initially containing the |
173 |
tim |
1.17 |
* elements of the given collection, |
174 |
dholmes |
1.16 |
* added in traversal order of the collection's iterator. |
175 |
jsr166 |
1.50 |
* |
176 |
dholmes |
1.16 |
* @param capacity the capacity of this queue |
177 |
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* @param fair if <tt>true</tt> then queue accesses for threads blocked |
178 |
jsr166 |
1.50 |
* on insertion or removal, are processed in FIFO order; |
179 |
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* if <tt>false</tt> the access order is unspecified. |
180 |
dholmes |
1.16 |
* @param c the collection of elements to initially contain |
181 |
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* @throws IllegalArgumentException if <tt>capacity</tt> is less than |
182 |
jsr166 |
1.50 |
* <tt>c.size()</tt>, or less than 1. |
183 |
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* @throws NullPointerException if the specified collection or any |
184 |
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* of its elements are null |
185 |
dholmes |
1.16 |
*/ |
186 |
tim |
1.20 |
public ArrayBlockingQueue(int capacity, boolean fair, |
187 |
dholmes |
1.18 |
Collection<? extends E> c) { |
188 |
dl |
1.36 |
this(capacity, fair); |
189 |
dholmes |
1.16 |
if (capacity < c.size()) |
190 |
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throw new IllegalArgumentException(); |
191 |
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|
192 |
jsr166 |
1.57 |
for (E e : c) |
193 |
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add(e); |
194 |
dholmes |
1.16 |
} |
195 |
dl |
1.2 |
|
196 |
dholmes |
1.13 |
/** |
197 |
jsr166 |
1.50 |
* Inserts the specified element at the tail of this queue if it is |
198 |
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* possible to do so immediately without exceeding the queue's capacity, |
199 |
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* returning <tt>true</tt> upon success and throwing an |
200 |
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* <tt>IllegalStateException</tt> if this queue is full. |
201 |
dl |
1.25 |
* |
202 |
jsr166 |
1.50 |
* @param e the element to add |
203 |
jsr166 |
1.52 |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
204 |
jsr166 |
1.50 |
* @throws IllegalStateException if this queue is full |
205 |
|
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* @throws NullPointerException if the specified element is null |
206 |
|
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*/ |
207 |
|
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public boolean add(E e) { |
208 |
jsr166 |
1.56 |
return super.add(e); |
209 |
jsr166 |
1.50 |
} |
210 |
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|
211 |
|
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/** |
212 |
|
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* Inserts the specified element at the tail of this queue if it is |
213 |
|
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* possible to do so immediately without exceeding the queue's capacity, |
214 |
|
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* returning <tt>true</tt> upon success and <tt>false</tt> if this queue |
215 |
|
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* is full. This method is generally preferable to method {@link #add}, |
216 |
|
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* which can fail to insert an element only by throwing an exception. |
217 |
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* |
218 |
|
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* @throws NullPointerException if the specified element is null |
219 |
dholmes |
1.13 |
*/ |
220 |
jsr166 |
1.49 |
public boolean offer(E e) { |
221 |
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if (e == null) throw new NullPointerException(); |
222 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
223 |
dl |
1.5 |
lock.lock(); |
224 |
|
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try { |
225 |
jsr166 |
1.59 |
if (count == items.length) |
226 |
dl |
1.2 |
return false; |
227 |
dl |
1.5 |
else { |
228 |
jsr166 |
1.49 |
insert(e); |
229 |
dl |
1.5 |
return true; |
230 |
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} |
231 |
tim |
1.23 |
} finally { |
232 |
tim |
1.12 |
lock.unlock(); |
233 |
dl |
1.2 |
} |
234 |
dl |
1.5 |
} |
235 |
dl |
1.2 |
|
236 |
dholmes |
1.13 |
/** |
237 |
jsr166 |
1.50 |
* Inserts the specified element at the tail of this queue, waiting |
238 |
|
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* for space to become available if the queue is full. |
239 |
|
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* |
240 |
|
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* @throws InterruptedException {@inheritDoc} |
241 |
|
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* @throws NullPointerException {@inheritDoc} |
242 |
|
|
*/ |
243 |
|
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public void put(E e) throws InterruptedException { |
244 |
|
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if (e == null) throw new NullPointerException(); |
245 |
|
|
final ReentrantLock lock = this.lock; |
246 |
|
|
lock.lockInterruptibly(); |
247 |
|
|
try { |
248 |
jsr166 |
1.59 |
while (count == items.length) |
249 |
jsr166 |
1.58 |
notFull.await(); |
250 |
jsr166 |
1.50 |
insert(e); |
251 |
|
|
} finally { |
252 |
|
|
lock.unlock(); |
253 |
|
|
} |
254 |
|
|
} |
255 |
|
|
|
256 |
|
|
/** |
257 |
|
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* Inserts the specified element at the tail of this queue, waiting |
258 |
|
|
* up to the specified wait time for space to become available if |
259 |
|
|
* the queue is full. |
260 |
|
|
* |
261 |
|
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* @throws InterruptedException {@inheritDoc} |
262 |
|
|
* @throws NullPointerException {@inheritDoc} |
263 |
brian |
1.7 |
*/ |
264 |
jsr166 |
1.49 |
public boolean offer(E e, long timeout, TimeUnit unit) |
265 |
dholmes |
1.13 |
throws InterruptedException { |
266 |
dl |
1.2 |
|
267 |
jsr166 |
1.49 |
if (e == null) throw new NullPointerException(); |
268 |
jsr166 |
1.56 |
long nanos = unit.toNanos(timeout); |
269 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
270 |
dl |
1.5 |
lock.lockInterruptibly(); |
271 |
|
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try { |
272 |
jsr166 |
1.59 |
while (count == items.length) { |
273 |
dl |
1.5 |
if (nanos <= 0) |
274 |
|
|
return false; |
275 |
jsr166 |
1.58 |
nanos = notFull.awaitNanos(nanos); |
276 |
dl |
1.5 |
} |
277 |
jsr166 |
1.58 |
insert(e); |
278 |
|
|
return true; |
279 |
tim |
1.23 |
} finally { |
280 |
dl |
1.5 |
lock.unlock(); |
281 |
dl |
1.2 |
} |
282 |
dl |
1.5 |
} |
283 |
dl |
1.2 |
|
284 |
dholmes |
1.13 |
public E poll() { |
285 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
286 |
dholmes |
1.13 |
lock.lock(); |
287 |
|
|
try { |
288 |
jsr166 |
1.59 |
return (count == 0) ? null : extract(); |
289 |
tim |
1.23 |
} finally { |
290 |
tim |
1.15 |
lock.unlock(); |
291 |
dholmes |
1.13 |
} |
292 |
|
|
} |
293 |
|
|
|
294 |
jsr166 |
1.50 |
public E take() throws InterruptedException { |
295 |
|
|
final ReentrantLock lock = this.lock; |
296 |
|
|
lock.lockInterruptibly(); |
297 |
|
|
try { |
298 |
jsr166 |
1.59 |
while (count == 0) |
299 |
jsr166 |
1.58 |
notEmpty.await(); |
300 |
|
|
return extract(); |
301 |
jsr166 |
1.50 |
} finally { |
302 |
|
|
lock.unlock(); |
303 |
|
|
} |
304 |
|
|
} |
305 |
|
|
|
306 |
dl |
1.5 |
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
307 |
jsr166 |
1.56 |
long nanos = unit.toNanos(timeout); |
308 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
309 |
dl |
1.5 |
lock.lockInterruptibly(); |
310 |
|
|
try { |
311 |
jsr166 |
1.59 |
while (count == 0) { |
312 |
dl |
1.5 |
if (nanos <= 0) |
313 |
|
|
return null; |
314 |
jsr166 |
1.58 |
nanos = notEmpty.awaitNanos(nanos); |
315 |
dl |
1.2 |
} |
316 |
jsr166 |
1.58 |
return extract(); |
317 |
tim |
1.23 |
} finally { |
318 |
dl |
1.5 |
lock.unlock(); |
319 |
|
|
} |
320 |
|
|
} |
321 |
dl |
1.2 |
|
322 |
dholmes |
1.13 |
public E peek() { |
323 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
324 |
dholmes |
1.13 |
lock.lock(); |
325 |
|
|
try { |
326 |
jsr166 |
1.59 |
return (count == 0) ? null : items[takeIndex]; |
327 |
tim |
1.23 |
} finally { |
328 |
dholmes |
1.13 |
lock.unlock(); |
329 |
|
|
} |
330 |
|
|
} |
331 |
|
|
|
332 |
|
|
// this doc comment is overridden to remove the reference to collections |
333 |
|
|
// greater in size than Integer.MAX_VALUE |
334 |
tim |
1.15 |
/** |
335 |
dl |
1.25 |
* Returns the number of elements in this queue. |
336 |
|
|
* |
337 |
jsr166 |
1.50 |
* @return the number of elements in this queue |
338 |
dholmes |
1.13 |
*/ |
339 |
|
|
public int size() { |
340 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
341 |
dholmes |
1.13 |
lock.lock(); |
342 |
|
|
try { |
343 |
|
|
return count; |
344 |
tim |
1.23 |
} finally { |
345 |
dholmes |
1.13 |
lock.unlock(); |
346 |
|
|
} |
347 |
|
|
} |
348 |
|
|
|
349 |
|
|
// this doc comment is a modified copy of the inherited doc comment, |
350 |
|
|
// without the reference to unlimited queues. |
351 |
tim |
1.15 |
/** |
352 |
jsr166 |
1.48 |
* Returns the number of additional elements that this queue can ideally |
353 |
|
|
* (in the absence of memory or resource constraints) accept without |
354 |
dholmes |
1.13 |
* blocking. This is always equal to the initial capacity of this queue |
355 |
|
|
* less the current <tt>size</tt> of this queue. |
356 |
jsr166 |
1.48 |
* |
357 |
|
|
* <p>Note that you <em>cannot</em> always tell if an attempt to insert |
358 |
|
|
* an element will succeed by inspecting <tt>remainingCapacity</tt> |
359 |
|
|
* because it may be the case that another thread is about to |
360 |
jsr166 |
1.50 |
* insert or remove an element. |
361 |
dholmes |
1.13 |
*/ |
362 |
|
|
public int remainingCapacity() { |
363 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
364 |
dholmes |
1.13 |
lock.lock(); |
365 |
|
|
try { |
366 |
|
|
return items.length - count; |
367 |
tim |
1.23 |
} finally { |
368 |
dholmes |
1.13 |
lock.unlock(); |
369 |
|
|
} |
370 |
|
|
} |
371 |
|
|
|
372 |
jsr166 |
1.50 |
/** |
373 |
|
|
* Removes a single instance of the specified element from this queue, |
374 |
|
|
* if it is present. More formally, removes an element <tt>e</tt> such |
375 |
|
|
* that <tt>o.equals(e)</tt>, if this queue contains one or more such |
376 |
|
|
* elements. |
377 |
|
|
* Returns <tt>true</tt> if this queue contained the specified element |
378 |
|
|
* (or equivalently, if this queue changed as a result of the call). |
379 |
|
|
* |
380 |
jsr166 |
1.64 |
* <p>Removal of interior elements in circular array based queues |
381 |
dl |
1.60 |
* is an intrinsically slow and disruptive operation, so should |
382 |
|
|
* be undertaken only in exceptional circumstances, ideally |
383 |
|
|
* only when the queue is known not to be accessible by other |
384 |
|
|
* threads. |
385 |
|
|
* |
386 |
jsr166 |
1.50 |
* @param o element to be removed from this queue, if present |
387 |
|
|
* @return <tt>true</tt> if this queue changed as a result of the call |
388 |
|
|
*/ |
389 |
|
|
public boolean remove(Object o) { |
390 |
|
|
if (o == null) return false; |
391 |
|
|
final E[] items = this.items; |
392 |
|
|
final ReentrantLock lock = this.lock; |
393 |
|
|
lock.lock(); |
394 |
|
|
try { |
395 |
|
|
int i = takeIndex; |
396 |
|
|
int k = 0; |
397 |
|
|
for (;;) { |
398 |
|
|
if (k++ >= count) |
399 |
|
|
return false; |
400 |
|
|
if (o.equals(items[i])) { |
401 |
|
|
removeAt(i); |
402 |
|
|
return true; |
403 |
|
|
} |
404 |
|
|
i = inc(i); |
405 |
|
|
} |
406 |
|
|
|
407 |
|
|
} finally { |
408 |
|
|
lock.unlock(); |
409 |
|
|
} |
410 |
|
|
} |
411 |
dholmes |
1.13 |
|
412 |
jsr166 |
1.50 |
/** |
413 |
|
|
* Returns <tt>true</tt> if this queue contains the specified element. |
414 |
|
|
* More formally, returns <tt>true</tt> if and only if this queue contains |
415 |
|
|
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
416 |
|
|
* |
417 |
|
|
* @param o object to be checked for containment in this queue |
418 |
|
|
* @return <tt>true</tt> if this queue contains the specified element |
419 |
|
|
*/ |
420 |
dholmes |
1.21 |
public boolean contains(Object o) { |
421 |
|
|
if (o == null) return false; |
422 |
dl |
1.36 |
final E[] items = this.items; |
423 |
|
|
final ReentrantLock lock = this.lock; |
424 |
dl |
1.5 |
lock.lock(); |
425 |
|
|
try { |
426 |
|
|
int i = takeIndex; |
427 |
|
|
int k = 0; |
428 |
|
|
while (k++ < count) { |
429 |
dholmes |
1.21 |
if (o.equals(items[i])) |
430 |
dl |
1.2 |
return true; |
431 |
dl |
1.5 |
i = inc(i); |
432 |
|
|
} |
433 |
dl |
1.2 |
return false; |
434 |
tim |
1.23 |
} finally { |
435 |
dl |
1.5 |
lock.unlock(); |
436 |
|
|
} |
437 |
|
|
} |
438 |
brian |
1.7 |
|
439 |
jsr166 |
1.50 |
/** |
440 |
|
|
* Returns an array containing all of the elements in this queue, in |
441 |
|
|
* proper sequence. |
442 |
|
|
* |
443 |
|
|
* <p>The returned array will be "safe" in that no references to it are |
444 |
|
|
* maintained by this queue. (In other words, this method must allocate |
445 |
|
|
* a new array). The caller is thus free to modify the returned array. |
446 |
jsr166 |
1.51 |
* |
447 |
jsr166 |
1.50 |
* <p>This method acts as bridge between array-based and collection-based |
448 |
|
|
* APIs. |
449 |
|
|
* |
450 |
|
|
* @return an array containing all of the elements in this queue |
451 |
|
|
*/ |
452 |
dl |
1.5 |
public Object[] toArray() { |
453 |
dl |
1.36 |
final E[] items = this.items; |
454 |
|
|
final ReentrantLock lock = this.lock; |
455 |
dl |
1.5 |
lock.lock(); |
456 |
|
|
try { |
457 |
dl |
1.34 |
Object[] a = new Object[count]; |
458 |
dl |
1.5 |
int k = 0; |
459 |
|
|
int i = takeIndex; |
460 |
|
|
while (k < count) { |
461 |
dl |
1.2 |
a[k++] = items[i]; |
462 |
dl |
1.5 |
i = inc(i); |
463 |
|
|
} |
464 |
dl |
1.2 |
return a; |
465 |
tim |
1.23 |
} finally { |
466 |
dl |
1.5 |
lock.unlock(); |
467 |
|
|
} |
468 |
|
|
} |
469 |
brian |
1.7 |
|
470 |
jsr166 |
1.50 |
/** |
471 |
|
|
* Returns an array containing all of the elements in this queue, in |
472 |
|
|
* proper sequence; the runtime type of the returned array is that of |
473 |
|
|
* the specified array. If the queue fits in the specified array, it |
474 |
|
|
* is returned therein. Otherwise, a new array is allocated with the |
475 |
|
|
* runtime type of the specified array and the size of this queue. |
476 |
|
|
* |
477 |
|
|
* <p>If this queue fits in the specified array with room to spare |
478 |
|
|
* (i.e., the array has more elements than this queue), the element in |
479 |
|
|
* the array immediately following the end of the queue is set to |
480 |
|
|
* <tt>null</tt>. |
481 |
|
|
* |
482 |
|
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
483 |
|
|
* array-based and collection-based APIs. Further, this method allows |
484 |
|
|
* precise control over the runtime type of the output array, and may, |
485 |
|
|
* under certain circumstances, be used to save allocation costs. |
486 |
|
|
* |
487 |
|
|
* <p>Suppose <tt>x</tt> is a queue known to contain only strings. |
488 |
|
|
* The following code can be used to dump the queue into a newly |
489 |
|
|
* allocated array of <tt>String</tt>: |
490 |
|
|
* |
491 |
|
|
* <pre> |
492 |
|
|
* String[] y = x.toArray(new String[0]);</pre> |
493 |
|
|
* |
494 |
|
|
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
495 |
|
|
* <tt>toArray()</tt>. |
496 |
|
|
* |
497 |
|
|
* @param a the array into which the elements of the queue are to |
498 |
|
|
* be stored, if it is big enough; otherwise, a new array of the |
499 |
|
|
* same runtime type is allocated for this purpose |
500 |
|
|
* @return an array containing all of the elements in this queue |
501 |
|
|
* @throws ArrayStoreException if the runtime type of the specified array |
502 |
|
|
* is not a supertype of the runtime type of every element in |
503 |
|
|
* this queue |
504 |
|
|
* @throws NullPointerException if the specified array is null |
505 |
|
|
*/ |
506 |
dl |
1.5 |
public <T> T[] toArray(T[] a) { |
507 |
dl |
1.36 |
final E[] items = this.items; |
508 |
|
|
final ReentrantLock lock = this.lock; |
509 |
dl |
1.5 |
lock.lock(); |
510 |
|
|
try { |
511 |
|
|
if (a.length < count) |
512 |
dholmes |
1.16 |
a = (T[])java.lang.reflect.Array.newInstance( |
513 |
tim |
1.17 |
a.getClass().getComponentType(), |
514 |
dholmes |
1.16 |
count |
515 |
|
|
); |
516 |
tim |
1.12 |
|
517 |
dl |
1.5 |
int k = 0; |
518 |
|
|
int i = takeIndex; |
519 |
|
|
while (k < count) { |
520 |
dl |
1.2 |
a[k++] = (T)items[i]; |
521 |
dl |
1.5 |
i = inc(i); |
522 |
|
|
} |
523 |
|
|
if (a.length > count) |
524 |
|
|
a[count] = null; |
525 |
dl |
1.2 |
return a; |
526 |
tim |
1.23 |
} finally { |
527 |
dl |
1.5 |
lock.unlock(); |
528 |
|
|
} |
529 |
|
|
} |
530 |
dl |
1.6 |
|
531 |
|
|
public String toString() { |
532 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
533 |
dl |
1.6 |
lock.lock(); |
534 |
|
|
try { |
535 |
|
|
return super.toString(); |
536 |
tim |
1.23 |
} finally { |
537 |
dl |
1.6 |
lock.unlock(); |
538 |
|
|
} |
539 |
|
|
} |
540 |
tim |
1.12 |
|
541 |
dl |
1.44 |
/** |
542 |
|
|
* Atomically removes all of the elements from this queue. |
543 |
|
|
* The queue will be empty after this call returns. |
544 |
|
|
*/ |
545 |
dl |
1.30 |
public void clear() { |
546 |
dl |
1.36 |
final E[] items = this.items; |
547 |
|
|
final ReentrantLock lock = this.lock; |
548 |
dl |
1.30 |
lock.lock(); |
549 |
|
|
try { |
550 |
|
|
int i = takeIndex; |
551 |
|
|
int k = count; |
552 |
|
|
while (k-- > 0) { |
553 |
|
|
items[i] = null; |
554 |
|
|
i = inc(i); |
555 |
|
|
} |
556 |
|
|
count = 0; |
557 |
|
|
putIndex = 0; |
558 |
|
|
takeIndex = 0; |
559 |
|
|
notFull.signalAll(); |
560 |
|
|
} finally { |
561 |
|
|
lock.unlock(); |
562 |
|
|
} |
563 |
|
|
} |
564 |
|
|
|
565 |
jsr166 |
1.50 |
/** |
566 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
567 |
|
|
* @throws ClassCastException {@inheritDoc} |
568 |
|
|
* @throws NullPointerException {@inheritDoc} |
569 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
570 |
|
|
*/ |
571 |
dl |
1.30 |
public int drainTo(Collection<? super E> c) { |
572 |
|
|
if (c == null) |
573 |
|
|
throw new NullPointerException(); |
574 |
|
|
if (c == this) |
575 |
|
|
throw new IllegalArgumentException(); |
576 |
dl |
1.36 |
final E[] items = this.items; |
577 |
|
|
final ReentrantLock lock = this.lock; |
578 |
dl |
1.30 |
lock.lock(); |
579 |
|
|
try { |
580 |
|
|
int i = takeIndex; |
581 |
|
|
int n = 0; |
582 |
|
|
int max = count; |
583 |
|
|
while (n < max) { |
584 |
|
|
c.add(items[i]); |
585 |
|
|
items[i] = null; |
586 |
|
|
i = inc(i); |
587 |
|
|
++n; |
588 |
|
|
} |
589 |
|
|
if (n > 0) { |
590 |
|
|
count = 0; |
591 |
|
|
putIndex = 0; |
592 |
|
|
takeIndex = 0; |
593 |
|
|
notFull.signalAll(); |
594 |
|
|
} |
595 |
|
|
return n; |
596 |
|
|
} finally { |
597 |
|
|
lock.unlock(); |
598 |
|
|
} |
599 |
|
|
} |
600 |
|
|
|
601 |
jsr166 |
1.50 |
/** |
602 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
603 |
|
|
* @throws ClassCastException {@inheritDoc} |
604 |
|
|
* @throws NullPointerException {@inheritDoc} |
605 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
606 |
|
|
*/ |
607 |
dl |
1.30 |
public int drainTo(Collection<? super E> c, int maxElements) { |
608 |
|
|
if (c == null) |
609 |
|
|
throw new NullPointerException(); |
610 |
|
|
if (c == this) |
611 |
|
|
throw new IllegalArgumentException(); |
612 |
|
|
if (maxElements <= 0) |
613 |
|
|
return 0; |
614 |
dl |
1.36 |
final E[] items = this.items; |
615 |
|
|
final ReentrantLock lock = this.lock; |
616 |
dl |
1.30 |
lock.lock(); |
617 |
|
|
try { |
618 |
|
|
int i = takeIndex; |
619 |
|
|
int n = 0; |
620 |
|
|
int sz = count; |
621 |
jsr166 |
1.58 |
int max = (maxElements < count) ? maxElements : count; |
622 |
dl |
1.30 |
while (n < max) { |
623 |
|
|
c.add(items[i]); |
624 |
|
|
items[i] = null; |
625 |
|
|
i = inc(i); |
626 |
|
|
++n; |
627 |
|
|
} |
628 |
|
|
if (n > 0) { |
629 |
|
|
count -= n; |
630 |
|
|
takeIndex = i; |
631 |
|
|
notFull.signalAll(); |
632 |
|
|
} |
633 |
|
|
return n; |
634 |
|
|
} finally { |
635 |
|
|
lock.unlock(); |
636 |
|
|
} |
637 |
|
|
} |
638 |
|
|
|
639 |
|
|
|
640 |
brian |
1.7 |
/** |
641 |
dl |
1.60 |
* Returns an iterator over the elements in this queue in proper |
642 |
|
|
* sequence. The returned <tt>Iterator</tt> is "weakly |
643 |
|
|
* consistent" with respect to operations at the head and tail of |
644 |
|
|
* the queue, and will never throw {@link |
645 |
|
|
* ConcurrentModificationException}. It might return elements |
646 |
|
|
* that existed upon construction of the iterator but have since |
647 |
|
|
* been polled or taken, and might not return elements that have |
648 |
|
|
* since been added. Further, no consistency guarantees are made |
649 |
|
|
* with respect to "interior" removals occuring in concurrent |
650 |
|
|
* invocations of {@link Collection#remove(Object)} or {@link |
651 |
|
|
* Iterator#remove} occurring in other threads. |
652 |
|
|
* |
653 |
jsr166 |
1.63 |
* <p>The returned iterator supports the optional {@link Iterator#remove} |
654 |
dl |
1.60 |
* operation. However, removal of interior elements in circular |
655 |
|
|
* array based queues is an intrinsically slow and disruptive |
656 |
|
|
* operation, so should be undertaken only in exceptional |
657 |
|
|
* circumstances, ideally only when the queue is known not to be |
658 |
|
|
* accessible by other threads. |
659 |
brian |
1.7 |
* |
660 |
jsr166 |
1.50 |
* @return an iterator over the elements in this queue in proper sequence |
661 |
brian |
1.7 |
*/ |
662 |
dl |
1.5 |
public Iterator<E> iterator() { |
663 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
664 |
dl |
1.5 |
lock.lock(); |
665 |
|
|
try { |
666 |
dl |
1.2 |
return new Itr(); |
667 |
tim |
1.23 |
} finally { |
668 |
dl |
1.5 |
lock.unlock(); |
669 |
|
|
} |
670 |
|
|
} |
671 |
dl |
1.8 |
|
672 |
|
|
/** |
673 |
dl |
1.60 |
* Iterator for ArrayBlockingQueue. To maintain weak consistency |
674 |
|
|
* with respect to puts and takes, we (1) read ahead one slot, so |
675 |
|
|
* as to not report hasNext true but then not have an element to |
676 |
|
|
* return (2) ensure that each array slot is traversed at most |
677 |
|
|
* once (by tracking "remaining" elements); (3) skip over null |
678 |
|
|
* slots, which can occur if takes race ahead of iterators. |
679 |
|
|
* However, for circular array-based queues, we cannot rely on any |
680 |
|
|
* well established definition of what it means to be weakly |
681 |
|
|
* consistent with respect to interior removes since these may |
682 |
|
|
* require slot overwrites in the process of sliding elements to |
683 |
|
|
* cover gaps. So we settle for resiliency, operating on |
684 |
jsr166 |
1.62 |
* established apparent nexts, which may miss some elements that |
685 |
|
|
* have moved between calls to next. |
686 |
dl |
1.8 |
*/ |
687 |
dl |
1.5 |
private class Itr implements Iterator<E> { |
688 |
dl |
1.60 |
private int remaining; // Number of elements yet to be returned |
689 |
|
|
private int nextIndex; // Index of element to be returned by next |
690 |
|
|
private E nextItem; // Element to be returned by next call to next |
691 |
|
|
private E lastItem; // Element returned by last call to next |
692 |
|
|
private int lastRet; // Index of last element returned, or -1 if none |
693 |
tim |
1.12 |
|
694 |
dl |
1.5 |
Itr() { |
695 |
|
|
lastRet = -1; |
696 |
dl |
1.60 |
if ((remaining = count) > 0) |
697 |
|
|
nextItem = items[nextIndex = takeIndex]; |
698 |
dl |
1.5 |
} |
699 |
tim |
1.12 |
|
700 |
dl |
1.5 |
public boolean hasNext() { |
701 |
dl |
1.60 |
return remaining > 0; |
702 |
dl |
1.5 |
} |
703 |
tim |
1.12 |
|
704 |
dl |
1.5 |
public E next() { |
705 |
dl |
1.60 |
if (remaining <= 0) |
706 |
|
|
throw new NoSuchElementException(); |
707 |
dl |
1.36 |
final ReentrantLock lock = ArrayBlockingQueue.this.lock; |
708 |
dl |
1.5 |
lock.lock(); |
709 |
|
|
try { |
710 |
|
|
lastRet = nextIndex; |
711 |
dl |
1.60 |
E x = lastItem = nextItem; |
712 |
|
|
while (--remaining > 0) { |
713 |
|
|
if ((nextItem = items[nextIndex = inc(nextIndex)]) != null) |
714 |
|
|
break; |
715 |
|
|
} |
716 |
dl |
1.5 |
return x; |
717 |
tim |
1.23 |
} finally { |
718 |
tim |
1.12 |
lock.unlock(); |
719 |
dl |
1.2 |
} |
720 |
dl |
1.5 |
} |
721 |
tim |
1.12 |
|
722 |
dl |
1.5 |
public void remove() { |
723 |
dl |
1.36 |
final ReentrantLock lock = ArrayBlockingQueue.this.lock; |
724 |
dl |
1.5 |
lock.lock(); |
725 |
|
|
try { |
726 |
dl |
1.2 |
int i = lastRet; |
727 |
|
|
if (i == -1) |
728 |
|
|
throw new IllegalStateException(); |
729 |
|
|
lastRet = -1; |
730 |
jsr166 |
1.61 |
E x = lastItem; |
731 |
|
|
lastItem = null; |
732 |
|
|
if (x == items[i]) |
733 |
dl |
1.60 |
removeAt(i); // only remove if item still at index |
734 |
tim |
1.23 |
} finally { |
735 |
dl |
1.5 |
lock.unlock(); |
736 |
|
|
} |
737 |
|
|
} |
738 |
tim |
1.1 |
} |
739 |
dl |
1.60 |
|
740 |
tim |
1.1 |
} |