Java线程的状态

• 1 停止线程
• 2 线程休眠（sleep）
• 3 线程礼让（yield）
• 4 合并礼让（Join）
• 5 线程状态观测(Thread.State)
• 5 线程优先级(Priority)
• 5 守护线程（Daemon）

• 建议线程正常停止，不建议使用死循环
• 建议使用标志位
• 不要使用stop或者destroy等过时或者JDK不建议使用的方法

public class TestStop implements Runnable {
    private boolean flag = true;


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

    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 < 1000; i++) {
            System.out.println("Main Thread" + i);
            if (i == 900) {
                testStop.stop();
                System.out.println("线程停止了！");
            }


        }
    }
}

• sleep(ms) ：指定当前线程阻塞的毫秒数
• sleep存在异常InterruptedException
• sleep事件达到后线程进入就绪状态
• sleep可以模拟网络延时，倒计时等
• 每一个对象都有一个锁，sleep不会释放锁

• 让当前执行的线程暂停，但不阻塞
• 将线程从运行状态转为就绪状态
• 让CPU重新调度，礼让不一定成功！

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();
        System.out.println(Thread.currentThread().getName()+"线程停止执行");
    }

}

待次线程执行完成后，再执行其他线程，其他线程阻塞

public class TestJoin {
    public static void main(String[] args) throws InterruptedException {
        MyJoin myJoin = new MyJoin();
        Thread thread = new Thread(myJoin);
        thread.start();

        for (int i = 0; i < 1000; i++) {
            if (i == 200) {
                thread.join();
            }
            System.out.println("main" + i);
        }
    }
}


class MyJoin implements Runnable {

    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println("线程vip来了" + i);
        }

    }
}

Thread.State是枚举类型

public class TestState {
    public static void main(String[] args) {
        Thread thread = new Thread(()->{
            for (int i = 0; i < 5; i++) {
                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

        // 观察启动后
        thread.start(); // 启动线程
        state = thread.getState();
        System.out.println(state); // Run

        while (state != Thread.State.TERMINATED){
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            state = thread.getState(); // 更新线程状态
            System.out.println(state);
        }

        thread.start(); // 报错，已经死的线成不能start
    }
}

public class TestPriority {
    public static void main(String[] args) {
        MyPriority myPriority = new MyPriority();

        Thread t1 = new Thread(myPriority, "Thread1");
        Thread t2 = new Thread(myPriority, "Thread2");
        Thread t3 = new Thread(myPriority, "Thread3");
        Thread t4 = new Thread(myPriority, "Thread4");
        Thread t5 = new Thread(myPriority, "Thread5");

        t1.setPriority(10);
        t2.setPriority(8);
        t3.setPriority(6);
        t4.setPriority(3);
        t5.setPriority(1);

        t1.start();
        t2.start();
        t3.start();
        t4.start();
        t5.start();
    }

}

class MyPriority implements Runnable {

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName() + "say hello !!!");
    }

}

要先设置线程的优先级，然后在启动线程，优先级高表示被操作系统调度的几率高，优先级低表示被操作系统调度的几率低，所以不能百分百保证优先级高的线程肯定被先调度，还是要看处理器“心情"

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
虚拟机不能等待守护线程执行完毕
守护线程一般是记录操作日志，监控状态，垃圾回收等

	
	public class TestDaemon {
    public static void main(String[] args) {
        God god = new God();
        You you = new You();

        Thread t1 = new Thread(god);
        t1.setDaemon(true);   // 守护线程

        t1.start();

        new Thread(you).start(); // 用户线程
    }
}


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

}



class You implements Runnable{
    @Override
    public void run(){
        for (int i = 0; i < 10; i++) {
            System.out.println("你一生都开始的活着");
        }
        System.out.println("goodbye world");

    }

}