1.CountDownLatch

计数器减为0的时候开始后面的代码
CountDownLatch.countDown()
CountDownLatch.await()

package Demo;

import java.util.concurrent.CountDownLatch;

public class CountDownLatchDemo {
    public static void main(String[] args) throws InterruptedException {
        //CountDownLatch计数器
        //计数器归0的时候继续执行下面代码
        CountDownLatch c1 = new CountDownLatch(6);
        for(int i = 1;i <= 6;i++){
            new Thread(()->{
                System.out.println(Thread.currentThread().getName() + "Go");
                c1.countDown();
            },String.valueOf(i)).start();
        }
        c1.await();
        System.out.println("1");
    }
}

2.CyclicBarrier

上面的是减这个是加

package Demo;

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;

public class CyclicBarrierDemo {
    public static void main(String[] args) {
        CyclicBarrier c1 = new CyclicBarrier(7,()->{
            System.out.println("ok");
        });
        for (int i = 0; i < 7; i++) {
            final int temp = i;
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+ temp);
                try {
                    c1.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }).start();

        }

    }
}

3.Semaphore

信号量
相当于一个坑位

package Demo;

import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;

public class SemaphoreDemo {
    public static void main(String[] args) {
        Semaphore semaphore = new Semaphore(3);

        for (int i = 0; i < 6; i++) {
            new Thread(()->{
                try {

                    semaphore.acquire();
                    System.out.println("ok");
                    TimeUnit.SECONDS.sleep(1);
                    System.out.println("run");
                }catch (Exception e){
                    e.printStackTrace();
                }finally {
                    semaphore.release();

                }
            }).start();
            
        }
    }
}