多线程

多线程实现流程

• 定义一个MyThread类继承Thread类
• 在MyThread类中重写run()方法
• 创建MyThread类的对象
• 启动线程

setName()和getName()

public class MyThreadDemo {
    public static void main(String[] args) throws InterruptedException {
        MyThread s = new MyThread();
        s.setName("倒计时:");                //设置线程名称为倒计时：
        s.start();
        while (true){
            String time = String.valueOf(s.getTime());
            if ("0".equals(time)) {
                Thread.sleep(1);
                System.out.println("时间到");
                break;
            }
        }
    }
}
public class MyThread extends Thread{
    private int time=-1;
    public int getTime() {
        return this.time;
    }
    @Override
    public void run() {
        for (int i = 5; i >=0 ; i--) {
            this.time = i;
            System.out.println(getName()+this.time);            //获取线程名称
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

线程优先级设置

• setPriority()
• getPriority() ```java public class MyThreadDemo { public static void main(String[] args) throws InterruptedException {

    MyThread s = new MyThread();
    s.start();
    s.setPriority(2);        //设置线程优先级为2    范围为1-10
    while (true){
        String time = String.valueOf(s.getTime());
        if ("0".equals(time)) {
            Thread.sleep(1);
            System.out.println("时间到");
            break;
        }
    }

  } }

public class MyThread extends Thread{ private int time=-1; public int getTime() { return this.time; } @Override public void run() { for (int i = 5; i >=0 ; i—) { this.time = i; System.out.println(“该线程优先级:”+getPriority()+”\n倒计时”+this.time); //获取线程优先级 try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } } }

<a name="h2sTU"></a>
## 线程控制
- Thread.sleep()
- *.join()
- *.setDaemon()
```java
public class MyThread extends Thread{
    private int time;
    private int i;
    public int getTime() {
        return this.time;
    }
    public void seti(int i) {
        this.i = i;
    }
    @Override
    public void run() {
        for (int i = this.i; i >=0 ; i--) {
            this.time = i;
            System.out.println("倒计时"+this.time);
            try {
                Thread.sleep(1000);                //设置该线程等待1s后运行
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}
public class MyThreadDemo {
    public static void main(String[] args) throws InterruptedException {
        MyThread s1 = new MyThread();
        MyThread s2 = new MyThread();
        MyThread s3 = new MyThread();
        s1.seti(5);
        s2.seti(10);
        s3.seti(5);
        s2.setDaemon(true);                              //设置s2为守护线程，当只剩下守护线程在运行时，jvm虚拟机会退出
        s1.start();
        s1.join();                                       //设置当s1执行完后其他线程才会执行
        s2.start();
        s3.start();
        }
}

通过实现Runnable接口实现多线程

public class MyThread implements Runnable{
    private int time;
    public void run(){
        this.time = 100;
        while (true){
            if (this.time <= 0){
                break;
            }
            System.out.println(Thread.currentThread().getName()+"正在出售第"+time+"张票");
            this.time--;
        }
    }
}
public class MyThreadDemo {
    public static void main(String[] args) throws InterruptedException {
        MyThread r = new MyThread();
        Thread s1 = new Thread(r,"一号窗口");
        Thread s2 = new Thread(r,"二号窗口");
        Thread s3 = new Thread(r,"三号窗口");
        s1.start();
        s2.start();
        s3.start();
    }
}
//使用该方式开启多线程时使用Thread.currentThread().getName()访问该进程名

同步代码块

public class MyThread implements Runnable{
    private int time = 100;
    private Object obj = new Object();
    public void run(){
        while (true){
            synchronized (obj){
                if (this.time <= 0){
                    break;
                }
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName()+"正在出售第"+time+"张票");
                this.time--;
        }
        }
    }
}
public class MyThreadDemo {
    public static void main(String[] args) throws InterruptedException {
        MyThread r = new MyThread();
        Thread s1 = new Thread(r,"一号窗口");
        Thread s2 = new Thread(r,"二号窗口");
        Thread s3 = new Thread(r,"三号窗口");
        s1.start();
        s2.start();
        s3.start();
    }
}

同步方法

public class MyThread implements Runnable{
    private int time = 100;
    public void run(){
        while (true){
            f();
        }
    }
    private synchronized void f(){
        if (this.time <= 0){
            System.out.println("出售完毕");
            System.exit(0);
        }
        else {
            System.out.println(Thread.currentThread().getName()+this.time);
            this.time--;
        }
    }
}
public class MyThreadDemo {
    public static void main(String[] args) throws InterruptedException {
        MyThread r = new MyThread();
        Thread s1 = new Thread(r,"一号窗口");
        Thread s2 = new Thread(r,"二号窗口");
        Thread s3 = new Thread(r,"三号窗口");
        s1.start();
        s2.start();
        s3.start();
    }
}