线程五大状态

1. 线程的五大状态

2. 线程停止stop

1. 建议线程正常停止，-->利用次数，不建议死循环
   2 .建议使用标志位
2. 不要使用stop或destroy等JDK不建议使用的方法

public class TestStop implements Runnable{

    //1.设置一个标志位
    private boolean flag = true;

    @Override
    public void run() {
        int i =0;
        while (flag) {
            System.out.println("run...Thread" + i++);
        }
    }

    //2.设置一个公开的方法停止线程，转换标志位
    public void stop() {
        this.flag = false;
    }
    public static void main(String[] args) {
        TestStop testStop = new TestStop();
        new Thread(testStop).start();

        for (int i = 0; i < 100; i++) {
            System.out.println("main "+ i);
            if (i == 80) {
                testStop.stop();
                System.out.println("线程停止了");
            }
        }
    }
}

3. 线程休眠sleep

public class TestSleep {
    public static void main(String[] args) {
        try {
            tenDown();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        //获取系统当前时间
        Date startTime = new Date(System.currentTimeMillis());
        int count = 10;
        while (count >= 0){
            try {
                Thread.sleep(1000);
                System.out.println(new SimpleDateFormat("HH:mm:ss").format(startTime));
                startTime = new Date(System.currentTimeMillis());
                count--;
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    //模拟倒计时
    public static void tenDown() throws InterruptedException {
        int num = 10;
        while (true){
            Thread.sleep(1000);
            System.out.println(num--);
            if (num <= 0) break;;
        }
    }
}

4. 线程礼让yield

礼让不一定成功,看CPU心情

public class TestYield {
    public static void main(String[] args) {
        MyYield myYield = new MyYield();
        new Thread(myYield,"a").start();
        new Thread(myYield,"b").start();
    }
}

class MyYield implements Runnable{
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+"线程开始执行");
        Thread.yield();   //线程礼让
        System.out.println(Thread.currentThread().getName()+"线程停止执行");
    }
}

5. join合并线程

代此线程执行完成后，再执行其他线程，其他线程阻塞，可以理解为插队

public class TestJoin implements Runnable{
    @Override
    public void run() {
        for (int i = 0; i < 1000; i++) {
            System.out.println("VIP来了" + i);
        }
    }
    public static void main(String[] args) throws InterruptedException {

        //启动线程
        TestJoin testJoin = new TestJoin();
        Thread thread = new Thread(testJoin);
        thread.start();

        //主线程
        for (int i = 0; i < 500; i++) {
            System.out.println("main" + i);
            if (i == 200) {
                thread.join();
            }
        }
    }
}

6. 测试线程状态

public class TestState {
    public static void main(String[] args) throws InterruptedException {
        Thread thread = new Thread(()->{
            for (int i = 0; i < 5; i++) {//等待5s
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            System.out.println("---------");
        });

        //观察状态
        Thread.State state = thread.getState();
        System.out.println(state);  //NEW

        //启动后
        thread.start();
        state = thread.getState();
        System.out.println(state);  //RUN

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

7. 测试优先级

Thread.MIN_PRIORITY = 1;
Thread.MAX_PRIORITY = 10
先设置优先级，再启动start()

public class TestPriority {
    public static void main(String[] args) {
        //主线程默认优先级
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());

        MyPriority myPriority = new MyPriority();
        Thread t1 = new Thread(myPriority,"t1");
        Thread t2 = new Thread(myPriority,"t2");
        Thread t3 = new Thread(myPriority,"t3");
        Thread t4 = new Thread(myPriority,"t4");
        Thread t5 = new Thread(myPriority,"t5");

        //先设置优先级，再启动
        t1.start();

        t2.setPriority(6);
        t2.start();

        t3.setPriority(1);
        t3.start();

        t4.setPriority(Thread.MAX_PRIORITY);
        t4.start();

        t5.setPriority(8);
        t5.start();
    }
}

class MyPriority implements Runnable{
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());
    }
}

8. 守护线程

• 虚拟机必须确保用户线程执行完毕
• 虚拟机不用等待守护线程执行完毕
• 如垃圾回收机制gcc

//测试守护线程
//上帝守护你
public class TestDaemon {
    public static void main(String[] args) {
        God god = new God();
        YouAndMe ym = new YouAndMe();
        Thread thread = new Thread(god);
        thread.setDaemon(true);//默认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(ym).start();//用户线程启动
    }

}

class God implements Runnable{
    @Override
    public void run() {
        while (true){
            System.out.println("上帝保佑着你我");
        }
    }
}

class YouAndMe implements Runnable{
    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            System.out.println("你我活着");
        }
        System.out.println("Goodbye World------");
    }
}