java 多线程中  - 栅栏   就是用一个线程去等待，被唤醒的次数，如果次数和要等待的次数相同时开始执行

其原理个人理解：

设置一个线程安全的变量 CyclicBarrier barrier  中的一个计数变量  ，然后创建一个等待线程，一直wait 等待 这个计数变量修改时唤醒，

唤醒时然后判断该计数变量和创建时的 等待线程数进行比较，如果大于或者等于时，开始执行跳过wait

需要等待的线程每次执行完都需要调用barrier.await()  去修改这个计数变量

public class Test {

public static void startE() {

System.out.println("start E");

}

public static void main(String[] args) {

final int count = 3;

final CyclicBarrier barrier = new CyclicBarrier(count, new Runnable() {

@Override

public void run() {

for(int i=0;i<8;i++){

System.out.println("E "+i);

try {

Thread.sleep(1000);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

});

String [] Ids = {"A", "B", "C"};

int[] times = {2,4,5};

for (int i = 0; i < count; i++) {

new Thread(new Worker(Ids[i],times[i], barrier)).start();

}

new Thread(new Runnable() {

@Override

public void run() {

// TODO Auto-generated method stub

for(int i= 0 ;i<10;i++){

try {

Thread.sleep(1000);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

System.out.println("D "+i);

}

}

}).start();

}

}

class Worker implements Runnable {

final String id;

final CyclicBarrier barrier;

int times =0;

public Worker(final String ids,int times, final CyclicBarrier barrier) {

this.id = ids;

this.barrier = barrier;

this.times = times;

}

@Override

public void run() {

try {

for(int i=0;i

try {

Thread.sleep(1000);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

System.out.println(id+" "+i);

}

this.barrier.await();

} catch (InterruptedException e) {

e.printStackTrace();

} catch (BrokenBarrierException e) {

e.printStackTrace();

}

}

}