Java基础知识02-多线程

线程池

1.工作任务类

public class WorkTask implements Runnable {
    @Override
    public void run() {
        try {
            int r = (int)(Math.random()*10);
            Thread.sleep(r*1000);
            System.out.println(Thread.currentThread().getId() + " is over");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

2.创建无限多线程池方式：

public class CachedThreadPoolTest {
    public static void main(String[] args) {
        ExecutorService exec = Executors.newCachedThreadPool();
        for ( int i = 0; i < 20; i++ ) {
            exec.execute(new WorkTask());
        }
        // shutdown()：不会立即终止线程池，而是要等所有任务缓存队列中的任务都执行完后才终止，但再也不会接受新的任务
        exec.shutdown();
    }
}

3.创建一定数量的线程池方式：

public class FixedThreadPoolTest {
    public static void main(String[] args) {
        ExecutorService exec = Executors.newFixedThreadPool(3);
        for ( int i = 0; i < 20; i++ ) {
            exec.execute(new WorkTask());
        }
        exec.shutdown();
    }
}

4.创建一个线程的线程池方式：

public class SingleThreadExecutorTest {
    public static void main(String[] args) {
        ExecutorService exec = Executors.newSingleThreadExecutor();
        for ( int i = 0; i < 20; i++ ) {
            exec.execute(new WorkTask());
        }
        exec.shutdown();
    }
}