Java5 多线程(五)--CyclicBarrier同步的工具类

允许一系列的集合等待彼此,到达一个共同的障碍物点.
表示大家彼此等待,大家集合好后才开始出发,分散活动后又在指定的地点集合碰面,这就好比整个公司的人员利用周末时间集体郊游一样,先各自从家里出发到公司集合后,在同时出发到公园游玩,在指定的地点后再同时开始就餐,...
public static void main(String[] args) {
ExecutorService service = Executors.newCachedThreadPool();
final CyclicBarrier cb = new CyclicBarrier(3);
for (int i = 0; i < 3; i++) {
Runnable runnable = new Runnable() {
public void run() {
try {
Thread.sleep((long) (Math.random() * 10000));
System.out.println("线程"
+ Thread.currentThread().getName()
+ "即将到达集合地点1，当前已有"
+ (cb.getNumberWaiting() + 1)
+ "个已经到达，"
+ (cb.getNumberWaiting() == 2 ? "都到齐了，继续走啊"
: "正在等候"));
cb.await();//只有三个线程都到齐了才往下走

Thread.sleep((long) (Math.random() * 10000));
System.out.println("线程"
+ Thread.currentThread().getName()
+ "即将到达集合地点2，当前已有"
+ (cb.getNumberWaiting() + 1)
+ "个已经到达，"
+ (cb.getNumberWaiting() == 2 ? "都到齐了，继续走啊"
: "正在等候"));

cb.await();
Thread.sleep((long) (Math.random() * 10000));
System.out.println("线程"
+ Thread.currentThread().getName()
+ "即将到达集合地点3，当前已有"
+ (cb.getNumberWaiting() + 1)
+ "个已经到达，"
+ (cb.getNumberWaiting() == 2 ? "都到齐了，继续走啊"
: "正在等候"));

cb.await();
} catch (Exception e) {
e.printStackTrace();
}
}
};
service.execute(runnable);
}
service.shutdown();
}



在Api有一个使用CyclicBarrier的例子:
class Solver {

final int N;

final float[][] data;

final CyclicBarrier barrier;

class Worker implements Runnable {

int myRow;

Worker(int row) { myRow = row; }

public void run() {

while (!done()) {

processRow(myRow);

try {

barrier.await();//处理完一行在此等待,如果N个线程都完成了各自的行,都在此等待,然后
将会执行new CyclicBarrier(N,Runnbale)里面Runnable的代码,也就是合并行mergeRows();

} catch (InterruptedException ex) {

return;

} catch (BrokenBarrierException ex) {

return;

}

}

}

}

public Solver(float[][] matrix) {

data = matrix;

N = matrix.length;

barrier = new CyclicBarrier(N,

new Runnable() {

public void run() {

mergeRows(...);

}

});

for (int i = 0; i < N; ++i)

new Thread(new Worker(i)).start();

waitUntilDone();

}

}

在这里每个工作者(Worker)线程处理这个矩阵一行,然后在这个障碍物处等待,知道矩阵的所有行都被处理了,当所有的行都被处理了提供的Runnable障碍物被执行并且合并这些行,如果合并者确定了一个合并方案,然后将会返回(return),并且每个worker将终止.

转载请注明出处: http://blog.csdn.net/johnny901114/article/details/8695723