Java多线程02

线程五大状态

新建 就绪 阻塞 运行 死亡

线程停止

package com.guanxing.state;

//测试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--》设置一个标志位
//3.不要使用stop或destroy等过时的或JDK不建议使用的方法
public class TestStop implements Runnable{

    //1.定义一个标识符
    private boolean flag = true;

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

    //2.设置一个停止方法，切换标志位
    public void stop() {
        this.flag = false;
    }

    public static void main(String[] args) {
        TestStop ts01 = new TestStop();
        new Thread(ts01).start();

        for (int i = 0; i < 1000; i++) {
            System.out.println("main"+i);
            if (i==900) {
                //调用stop方法
                ts01.stop();
                System.out.println("线程已停止...");
            }
        }
    }
}

线程休眠

• sleep 指定当前线程阻塞的毫秒数
• sleep 存在异常 InterruptedException
• sleep 时间到达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

package com.guanxing.state;

import javax.sound.midi.Track;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.logging.SimpleFormatter;

//sleep模拟倒计时
public class TestSleep {

    public static void main(String[] args) {
        //打印当前系统时间
        Date startTime = new Date(System.currentTimeMillis());

        while (true) {
            try {
                System.out.println(new SimpleDateFormat("HH:mm:ss").format(startTime));
                Thread.sleep(1000);
                startTime = new Date(System.currentTimeMillis()); //更新当前时间
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        //调用倒计时函数
//        try {
//            tenDown(10);
//        } catch (InterruptedException e) {
//            e.printStackTrace();
//        }
    }

    public static void tenDown(int num) throws InterruptedException {
        while (num > 0) {
            Thread.sleep(1000);
            System.out.println(num--);
        }
    }
}

线程礼让

• 礼让线程 yield，让当前正在执行的线程暂停（非阻塞！）
• 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！看cpu心情

线程抢占

package com.guanxing.state;

public class TestJoin implements Runnable {
    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            System.out.println("线程vip来啦！都让一让！"+i);
        }
    }

    public static void main(String[] args) {
        TestJoin testJoin = new TestJoin();
        Thread thread = new Thread(testJoin);
        thread.start();

        for (int i = 0; i < 1000; i++) {
            if (i==200) {
                try {
                    thread.join();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            System.out.println("main线程正在执行..."+i);
        }
    }
}

观测线程状态

package com.guanxing.state;

public class TestState{

    public static void main(String[] args) throws InterruptedException {
        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 开始
        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);  //RUNNABLE

        while (state != Thread.State.TERMINATED) {//只要线程不终止就一直输出状态
            Thread.sleep(100);
            state = thread.getState();  //更新状态
            System.out.println(state);  //输出状态
        }

    }
}

/*
NEW
RUNNABLE
TIMED_WAITING
TIMED_WAITING
...
TIMED_WAITING
//////
TERMINATED
*/

线程优先级

优先级用数字表示，范围从1~10

使用以下方式改变或获取优先级

• getPriority()
• setPriority( int )

package com.guanxing.state;

public class TestPriority {
    public static void main(String[] args) {
        //先打印下main线程的
        System.out.println(Thread.currentThread().getName()+"--->"+Thread.currentThread().getPriority());

        Priority priority = new Priority();

        //多创建几个线程
        Thread t1 = new Thread(priority);
        Thread t2 = new Thread(priority);
        Thread t3 = new Thread(priority);
        Thread t4 = new Thread(priority);

        //启动前先设置优先级
        t1.setPriority(4);
        t1.start();

        t2.setPriority(5);
        t2.start();

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

        t4.setPriority(10);
        t4.start();
    }
}

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

/*
main--->5
Thread-3--->10
Thread-1--->5
Thread-0--->4
Thread-2--->1
 */

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
• 虚拟机不必等待守护线程执行完毕
• 如后台记录操作日志，监控内存，垃圾回收等等

package com.guanxing.state;

//测试守护线程
//上帝保佑着你
public class TestDaemon {
    public static void main(String[] args) {
        God god = new God();
        Person you = new Person();

        Thread godThread = new Thread(god);
        godThread.setDaemon(true);  //默认false表示用户线程，正常的线程都是用户线程...
        godThread.start(); //上帝守护线程启动

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

//定义一个上帝类
class God implements Runnable {
    @Override
    public void run() {
        while (true) {
            System.out.println("上帝保佑着你！");
        }
    }
}

//定义一个人类
class Person implements Runnable {
    @Override
    public void run() {
        for (int i = 0; i < 1000; i++) {
            System.out.println("每一天都要过的开开心心~");
        }
        System.out.println("========Goodbye World!========");
    }
}