并发

Callable

1  可以返回值

2可以抛出异常

泛型指的是返回值的类型

public class Send {public static void main(String[] args) {//怎么启动Callable//new Thread().start();Aaa thread=new Aaa();FutureTask futureTask=new FutureTask(thread);new Thread(futureTask,"name").start();}
}
class Aaa implements Callable<String> {@Overridepublic String call() throws Exception {System.out.println("sssss");return "ssss";}
}

CountDownLatch（倒计时）

value(of）返回本身的值

每次有线程调用countDown()数量-1，假设计数器变为0，countDownLatch.await()就会被唤醒，继续执行! 

public class Send {public static void main(String[] args) throws InterruptedException {//倒计时CountDownLatch count=new CountDownLatch(6);for (int i = 0; i < 6; i++) {new Thread(()->{System.out.println(Thread.currentThread().getName()+"GO out");count.countDown();//数量-1},String.valueOf(i)).start();}count.await();//等待计数器归零然后在向下执行}
}

CyclicBarrier（倒计时）

public class Send {public static void main(String[] args) {CyclicBarrier cyclicBarrier=new CyclicBarrier(7,()->{System.out.println("召唤神龙");});for (int i = 0; i <7; i++) {final  int temp =i;//lambda能操作i吗  线程里只能通过final类型的的变量操作inew Thread(()->{System.out.println(Thread.currentThread().getName()+"收集了"+temp);try {cyclicBarrier.await();//等待} catch (InterruptedException e) {throw new RuntimeException(e);} catch (BrokenBarrierException e) {throw new RuntimeException(e);}}).start();}}
}

semaphore

public class Send {public static void main(String[] args) {//线程数量：停车位Semaphore semaphore=new Semaphore(3);for (int i = 0; i <7; i++) {new Thread(()->{//acquire()得到try {semaphore.acquire();System.out.println(Thread.currentThread().getName()+"抢到了");Thread.sleep(2000);} catch (InterruptedException e) {throw new RuntimeException(e);}//release释放semaphore.release();System.out.println(Thread.currentThread().getName()+"离开了");}).start();}}
}

 semaphore.acquire();获得假设已经满了 等待被释放为止

semaphore.release（）释放 会将当前的信号量是释放

作用:多个共享资源互斥的使用!并发限流，控制最大的线程数