观测线程状态、守护线程

public class TestState implements Runnable{
    @Override
    public void run() {
        for (int i = 0; i < 50; i++) {
            System.out.println("现在是第"+i+"个");
            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        
        TestState testState = new TestState();
        Thread thread = new Thread(testState);
        //观察状态
        Thread.State state = thread.getState();
        System.out.println(state);
        //观察启动后
        thread.start();
        state = thread.getState();
        System.out.println(state);//run

        while(state!= Thread.State.TERMINATED){//只要线程不停止，一直输出
            thread.sleep(100);
            state = thread.getState();
            System.out.println(state);//输出状态
        }

    }
}

守护线程

线程分为用户线程和守护线程

虚拟机必须确保用户线程执行完毕，但不用等待守护线程执行完毕，如后台记录操作日志，监控内存，垃圾回收等待

//测试守护线程
//上帝守护你
public class TestDaemon {

    public static void main(String[] args) {
        God god = new God();
        You you = new You;
        Thread thread = new Thread(god);
        thread.setDaemon(true);//默认是false是用户线程，正常线程都是用户线程
        
        thread.start();//上帝守护线程启动
        
        new Thread(new You()).start();
    }
}
//上帝
class God implements Runnable{
    @Override
    public void run() {
        while(true){
            System.out.println("baohu");
        }
    }
}
//你
class You implements Runnable{
    @Override
    public void run() {
        for (int i = 0; i < 36500; i++) {
            System.out.println("live");
        }
        System.out.println("over");
    }
}