1.Condition

• JUC Lock 线程间通信工具类

/**
 * Description:ConditionWait
 *
 * @date 2019-12-12 16:12
 */

public class ConditionWait  implements Runnable{
    
    private Lock lock;
    private Condition condition;

    public ConditionWait(Lock lock, Condition condition) {
        this.lock = lock;
        this.condition = condition;
    }

    @Override
    public void run() {
        lock.lock();//Step1:Wait线程抢占锁成功
        try {
            System.out.println("begin ConditionWait");//Step2:Wait线程condition.await()
            condition.await();//
            System.out.println("end ConditionWait");
        }catch (Exception e){
            e.printStackTrace();
        }
        finally {
            lock.unlock();
        }
    }
}

/**
 * Description:ConditionNotify
 *
 * @date 2019-12-12 16:25
 */

public class ConditionNotify implements Runnable{

    private Lock lock;
    private Condition condition;

    public ConditionNotify(Lock lock, Condition condition) {
        this.lock = lock;
        this.condition = condition;
    }

    @Override
    public void run() {
        lock.lock();//
        try {
            System.out.println("begin ConditionNotify");
            condition.signal();//Step3:Notify线程condition.signal()
            System.out.println("end ConditionNotify");
        }catch (Exception e){
            e.printStackTrace();
        }
        finally {
            lock.unlock();
        }
    }

    public static void main(String[] args) {
        Lock lock = new ReentrantLock();
        Condition condition = lock.newCondition();

        new Thread(new ConditionWait(lock,condition)).start();
        new Thread(new ConditionNotify(lock,condition)).start();

    }
}

• 执行结果:

begin ConditionWait
begin ConditionNotify
end ConditionNotify
end ConditionWait

• 流程图

  
  image.png

2.CountDownLatch

• 倒计时计数器
• 主要方法 .await() .countDown()

public class CountDownLatchDemo {


    public static void main(String[] args) throws Exception{

        CountDownLatch countDownLatch = new CountDownLatch(3);//countDownLatch = 3
        new Thread(()->{
           countDownLatch.countDown();//countDownLatch-=1
        }).start();
        new Thread(()->{
           countDownLatch.countDown();//countDownLatch-=1
        }).start();
        new Thread(()->{
            countDownLatch.countDown();//countDownLatch-=1
        }).start();
        countDownLatch.await();//阻塞当前线程,直到countDownLatch=0
    }
}

3.Semaphore

• ''限流器"

public class SemaphoreDemo implements Runnable {

    private int num;
    private Semaphore semaphore;

    public SemaphoreDemo(int num, Semaphore semaphore) {
        this.num = num;
        this.semaphore = semaphore;
    }

    @Override
    public void run() {
        try {
            semaphore.acquire();//获取一个令牌,如果取不到阻塞
            System.out.println("第"+num+"个线程 抢占令牌");
            Thread.sleep(2000);
            System.out.println("第"+num+"个线程 释放令牌");
            semaphore.release();//释放令牌
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {

        Semaphore semaphore = new Semaphore(10);//设置令牌总数:10
        for(int i=0;i<100;i++){
            new Thread(new  SemaphoreDemo(i,semaphore)).start();
        }
    }

4.CyclicBarrier

• "循环栅栏"

public class CyclicBarrierDemo implements Runnable {

    private int code;
    private CyclicBarrier cyclicBarrier;

    public CyclicBarrierDemo(int code, CyclicBarrier cyclicBarrier) {
        this.code = code;
        this.cyclicBarrier = cyclicBarrier;
    }

    @Override
    public void run() {
        System.out.println("编号:"+code+"的学员已经就位");
        try {
            cyclicBarrier.await();//阻塞,直到去除屏障
        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    public static void main(String[] args) {
        CyclicBarrier cyclicBarrier = new CyclicBarrier(3, new Thread(()->{
            System.out.println("人员到齐,出发");
        }));

        new Thread( new CyclicBarrierDemo(1,cyclicBarrier)).start();
        new Thread( new CyclicBarrierDemo(2,cyclicBarrier)).start();
        new Thread( new CyclicBarrierDemo(3,cyclicBarrier)).start();

    }