BlockingQueue之ArrayBlockingQueue类的测试

在Java中，BlockingQueue是一个接口，它的实现类有如下

・ArrayBlockingQueue、

ArrayBlockingQueue底层是使用一个数组实现队列的，并且在构造ArrayBlockingQueue时需要指定容量，

也就意味着底层数组一旦创建了，容量就不能改变了，因此ArrayBlockingQueue是一个容量限制的阻塞队列。

因此，在队列全满时执行入队将会阻塞，在队列为空时出队同样将会阻塞。

ArrayBlockingQueue的并发阻塞是通过ReentrantLock和Condition来实现的，ArrayBlockingQueue内部只有一把锁，

意味着同一时刻只有一个线程能进行入队或者出队的操作。

・DelayQueue、

 

・LinkedBlockingDeque、

・LinkedBlockingQueue、

LinkedBlockingQueue是一个基于链表实现的可选容量的阻塞队列。

队头的元素是插入时间最长的，队尾的元素是最新插入的。新的元素将会被插入到队列的尾部。 

LinkedBlockingQueue的容量限制是可选的，

如果在初始化时没有指定容量，那么默认使用int的最大值作为队列容量。

LinkedBlockingQueue中维持两把锁，一把锁用于入队，一把锁用于出队，这也就意味着，同一时刻，

只能有一个线程执行入队，其余执行入队的线程将会被阻塞；同时，可以有另一个线程执行出队，

其余执行出队的线程将会被阻塞。换句话说，虽然入队和出队两个操作同时均只能有一个线程操作，

但是可以一个入队线程和一个出队线程共同执行，也就意味着可能同时有两个线程在操作队列，

那么为了维持线程安全，LinkedBlockingQueue使用一个AtomicInterger类型的变量表示当前队列中含有的元素个数，

所以可以确保两个线程之间操作底层队列是线程安全的。

・PriorityBlockingQueue、

・SynchronousQueue等，

 

※它们的区别主要体现在存储结构上或对元素操作上的不同，

　但是对于take与put操作的原理，却是类似的。

 

以上内容摘自如下页面

作者：天外流星for
链接：https://www.jianshu.com/p/7b2f1fa616c6
来源：简书

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package t1;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class TestThread25 {
public static void main(String[] args) {

final BlockingQueue<Character> bq = new ArrayBlockingQueue<>(26);
final ExecutorService es = Executors.newFixedThreadPool(2);
Runnable r = () -> {
for (char ch = 'A'; ch <= 'Z'; ch++) {
try {
bq.put(ch);
System.out.printf("%c produced by producer.%n", ch);// 能同步，但是输出顺序不能保证
} catch (InterruptedException e) {
}
}
};
es.execute(r);
Runnable r2 = () -> {
char ch = '\0';
do {
try {
ch = bq.take();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.printf("%c consumed by consumer.%n", ch);// 能同步，但是输出顺序不能保证
} while (ch != 'z');
};
es.execute(r2);
}
}

输出结果：

A produced by producer.
B produced by producer.
A consumed by consumer.
B consumed by consumer.
C consumed by consumer.
C produced by producer.
D produced by producer.
D consumed by consumer.
E consumed by consumer.
E produced by producer.
F produced by producer.
G produced by producer.
H produced by producer.
I produced by producer.
J produced by producer.
K produced by producer.
F consumed by consumer.
L produced by producer.
M produced by producer.
N produced by producer.
O produced by producer.
G consumed by consumer.
H consumed by consumer.
I consumed by consumer.
J consumed by consumer.
K consumed by consumer.
L consumed by consumer.
M consumed by consumer.
N consumed by consumer.
O consumed by consumer.
P consumed by consumer.
P produced by producer.
Q produced by producer.
Q consumed by consumer.
R consumed by consumer.
R produced by producer.
S produced by producer.
T produced by producer.
U produced by producer.
V produced by producer.
W produced by producer.
X produced by producer.
Y produced by producer.
Z produced by producer.
S consumed by consumer.
T consumed by consumer.
U consumed by consumer.
V consumed by consumer.
W consumed by consumer.
X consumed by consumer.
Y consumed by consumer.
Z consumed by consumer.