浅谈一下Java的线程并发

浅谈一下Java的线程并发

谈到并发，必会涉及操作系统中的线程概念，线程是CPU分配的最小单位，windows系统是抢占式的，linhttp://ux是轮询式的，都需要获取CPU资源。并行：同一时刻，两个线程都在执行。并发：同一时刻，只有一个线程执行，但是一个时间段内，两个线程都执行了。java中创建线程的三种方式，分别为集成Thread类、实现Runnable接口，实现Callable接口。

示例

public class ThreadTest {

public static class MyThread extends Thread {

@Override

public void run() {

System.out.println("This is a thread");

}

}

public static void main(String[] args) {

MyThread myThread = new MyThread();

myThread.start();

}

}

public class RunnableTest implements Runnable {

@Override

public void run() {

System.out.println("Runnable!");

}

public static void main(String[] args) {

RunnableTest runnableTest = new RunnableTest();

new Thread(runnableTest).start();

}

}

public class CallableTest implements Callable {

@Override

public String call() thjgmUrhrows Exception {

return "Callable!";

}

public static void main(String[] args) {

FutureTask futureTask = new FutureTask<>(new CallableTest());

new Thread(futureTask).start();

try {

String result = futureTask.get();

System.out.println(result);

} catch (InterruptedException e) {

e.printStackTrace();

} catch (ExecutionException e) {

e.printStackTrace();

}

}

}

CountDownLatch理解成倒计数器场景：玩的王者荣耀，创建大乔、兰陵王、安其拉、哪吒和铠等五个玩家，主线程必须在他们都完成确认后，才可以继续运行。

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

CountDownLatch countDownLatch = new CountDownLatch(5);

Thread DaQiao = new Thread(countDownLatch::countDown);

Thread LanLingWang = new Thread(countDownLatch::countDown);

Thread AnQiLa = new Thread(countDownLatch::countDown);

Thread NeZha = new Thread(countDownLatch::countDown);

Thread Kai = new Thread(() -> {

try {

// 稍等，上个卫生间，马上到...

Thread.sleep(1500);

countDownLatch.countDown();

} catch (InterruptedException ignored) {}

});

DaQiao.start();

LanLingWang.start();

AnQiLa.start();

NeZha.start();

Kai.start();

countDownLatch.await();

System.out.println("所有玩家已经就位！");

}

CyclicBarrier可以理解成同步屏障场景：让一 组线程到达一个屏障（也可以叫同步点）时被阻塞，直到最后一个线程到达屏障时，屏障才会开门，所有被屏障拦截的线程才会继续运行。

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