CyclicBarrier
应用场景是比如在做压力测试时,使用多少个用户并发,做集合点测试。
比如设置 100个用户并发,100个用户同时进行压测,只有100个用户压测完毕时,才能再发起下一波的压力测试。
package com.study.juc;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
public class CyclicBarrierDemo {
public static void main(String[] args) throws BrokenBarrierException, InterruptedException, TimeoutException {
CyclicBarrier cyclicBarrier=new CyclicBarrier(2,()->{
System.err.println( "集合完毕出发!");
});
for(int i=1;i<=3;i++){
int tmp = i;
new Thread(()->{
System.err.println(Thread.currentThread().getName() +"线程before:"+ tmp);
try {
cyclicBarrier.await(2, TimeUnit.SECONDS);
System.err.println(Thread.currentThread().getName() +"线程after:"+ tmp);
} catch (Exception e) {
e.printStackTrace();
}
},"CyclicBarrier").start();
}
}
}
CountDownLatch
减法计数器。
package com.study.juc;
import java.util.concurrent.CountDownLatch;
public class CountDownLatchDemo {
public static void main(String[] args) throws InterruptedException {
CountDownLatch latch=new CountDownLatch(13);
for(int i=1;i<=12;i++){
new Thread(()->{
System.err.println(Thread.currentThread().getName() +"before:" +latch.getCount());
latch.countDown();
System.err.println(Thread.currentThread().getName() +"after :" +latch.getCount());
},String.valueOf(i)).start();
}
latch.await();
}
}
使用信号量
public class SemaphoreDemo {
public static void main(String[] args) {
Semaphore semaphore=new Semaphore(3);
Random random=new Random();
for(int i=1;i<=6;i++){
new Thread(()->{
try {
semaphore.acquire();
int second=random.nextInt(10);
System.err.println(Thread.currentThread().getName() +"时长"+second +"开始");
TimeUnit.SECONDS.sleep(second);
System.err.println(Thread.currentThread().getName()+"完成");
}
catch (InterruptedException ex){
ex.printStackTrace();
}
finally {
semaphore.release();
}
},"线程" +i).start();
}
}
}
信号量的作用是:比如有三个车位,有6辆车,先进入三辆车,如果一辆车出来,后来的车可以进去,但始终只有三辆车同时停到车位。