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package org.rui.thread.newc; import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit; /**
* Latch 锁存器
* 新类库中的构件 countDownLatch
*
* @author lenovo
*
*/
class TaskPortion implements Runnable { private static int counter = 0;
private final int id = counter++;
private static Random rand = new Random(47); private final CountDownLatch latch; public TaskPortion(CountDownLatch latch) {
this.latch = latch;
} @Override
public void run() {
try {
doWork();
latch.countDown();
} catch (InterruptedException e) {
// acceptable way to exit
} } // 处理业务代码
public void doWork() throws InterruptedException {
TimeUnit.MILLISECONDS.sleep(rand.nextInt(2000));
System.out.println(this + " 完毕");
} public String toString() {
return String.format("%1$-3d", id);
} } // waits on the countDownLatch
class WaitingTask implements Runnable {
private static int counter = 0;// 计数
private final int id = counter++;
private static Random rand = new Random(47); private final CountDownLatch latch; WaitingTask(CountDownLatch latch) {
this.latch = latch;
} @Override
public void run() {
try {
// 调用countDown()的任务在产生调用时并没有被堵塞。仅仅有对await的调用会被堵塞，直至计数值到达0
// 等待问题被解决的任务在这个锁存器上调用await(),将它们自已拦住，直至锁存器计数结束
latch.await();
System.out.println("latch 障碍被觉得 " + this);
} catch (InterruptedException e) {
System.out.println(this + " interrupted");
}
} public String toString() {
return String.format("waitingTask %1$-3d", id);
}
} /**
* TaskPortio将随机地休眠一段时间，以模拟这部分工作的完毕，而WaitingTask表示系统中等待的部分。它要等待到问题的初始部分成完为止。
* 全部的任务都使用了在main中定义同一个单一的counDownLacth
*
* @author lenovo
*
*/
public class CountDownLatchDemo {
static final int SIZE = 100; public static void main(String[] args) throws InterruptedException {
ExecutorService exec = Executors.newCachedThreadPool();
CountDownLatch latch = new CountDownLatch(SIZE); // 都必须共享一个countDownLatch对象
for (int i = 0; i < 10; i++) {
exec.execute(new WaitingTask(latch));// 这个要等待 latch上面的为0时才会运行
}
for (int i = 0; i < SIZE; i++) {
exec.execute(new TaskPortion(latch));
} // latch.await();
System.out.println("launched all tasks");
exec.shutdown();// quit when all task complete
} }
/**
output:
launched all tasks
43 完毕
95 完毕
99 完毕
36 完毕
94 完毕
11 完毕
....
12 完毕
1 完毕
27 完毕
98 完毕
13 完毕
72 完毕
71 完毕
2 完毕
45 完毕
92 完毕
31 完毕
14 完毕
17 完毕
6 完毕
97 完毕
....
80 完毕
....
56 完毕
85 完毕
61 完毕
30 完毕
....
3 完毕
93 完毕
81 完毕
78 完毕
73 完毕
44 完毕
82 完毕
49 完毕
64 完毕
83 完毕
16 完毕
latch 障碍被觉得 waitingTask 2
latch 障碍被觉得 waitingTask 0
latch 障碍被觉得 waitingTask 4
latch 障碍被觉得 waitingTask 1
latch 障碍被觉得 waitingTask 5
latch 障碍被觉得 waitingTask 3
latch 障碍被觉得 waitingTask 7
latch 障碍被觉得 waitingTask 6
latch 障碍被觉得 waitingTask 9
latch 障碍被觉得 waitingTask 8
*/