CountDownLatch（闭锁）计数器
有一个任务A，它要等待其他4个任务执行完毕之后才执行，此时就可以利用CountDownLatch来实现这种功能
package com.cppdy;
import java.util.concurrent.CountDownLatch;
class MyThread17 extends Thread{
private CountDownLatch countdownlatch;
public MyThread17(CountDownLatch countdownlatch) {
this.countdownlatch=countdownlatch;
}
@Override
public void run() {
try {
sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(getName()+"线程执行完毕");
countdownlatch.countDown();
}
}
public class ThreadDemo17 {
public static void main(String[] args) throws Exception {
CountDownLatch cd=new CountDownLatch(2);
MyThread17 my1 = new MyThread17(cd);
MyThread17 my2 = new MyThread17(cd);
my1.start();
my2.start();
Thread.sleep(300);
cd.await();
System.out.println("主线程结束");
}
}
CyclicBarrier（回环栅栏）
CyclicBarrier初始化时规定一个数目，然后计算调用了CyclicBarrier.await()进入等待的线程数。当线程数达到这个数目时，所有进入等待状态的线程被唤醒并继续
package com.cppdy;
import java.util.concurrent.CyclicBarrier;
class MyThread18 extends Thread {
private CyclicBarrier cyclicBarrier;
public MyThread18(CyclicBarrier cyclicBarrier) {
this.cyclicBarrier = cyclicBarrier;
}
@Override
public void run() {
System.out.println("开始执行线程");
try {
sleep(2000);
//第一次进来，表示有一个线程等待，还不满足三个，不释放
//第二次进来，也不满足
//第三次进来，满足了，就继续执行下面的代码
cyclicBarrier.await();
} catch (Exception e) {
e.printStackTrace();
}
System.out.println("结束执行线程");
}
}
public class ThreadDemo18 {
public static void main(String[] args) throws Exception {
CyclicBarrier cb = new CyclicBarrier(3);
MyThread18 my1 = new MyThread18(cb);
MyThread18 my2 = new MyThread18(cb);
MyThread18 my3 = new MyThread18(cb);
my1.start();
my2.start();
my3.start();
System.out.println("主线程执行结束");
}
}
Semaphore（信号量）
Semaphore是一种基于计数的信号量，它可以设置一个阀值，多个线程竞争获取许可信号，做自己的申请后归还，超过阀值后，线程申请许可信号将会被阻塞
package com.cppdy; import java.util.Random;
import java.util.concurrent.Semaphore; class MyThread19 extends Thread {
private String name;
private Semaphore sp; public MyThread19(String name, Semaphore sp) {
this.name = name;
this.sp = sp;
} @Override
public void run() {
int availablePermits = sp.availablePermits();
if (availablePermits > 0) {
System.out.println(name + ",好开心啊，居然还有坑");
} else {
System.out.println(name + ",好伤心啊，怎么没有坑了");
}
try {
sp.acquire();
System.out.println(name + ",好开心啊，终于抢到啦");
//模拟上厕所时间
Thread.sleep(new Random().nextInt(1000));
System.out.println(name + ",好爽啊，终于上完啦");
sp.release();
} catch (Exception e) {
e.printStackTrace();
}
}
} public class ThreadDemo19 { public static void main(String[] args) throws Exception {
Semaphore sp = new Semaphore(3);
for (int i = 0; i < 10; i++) {
MyThread19 mt = new MyThread19("第" + i + "个人", sp);
mt.start();
}
} }