多线程学习笔记

多线程学习笔记

这是一篇关于多线程相关的一些学习笔记

继承Thread类

1、子类继承Thread类具备多线程能力

2、启动线程: 子类对象. start()

3、不建议使用:避免OOP单继承局限性

//创建线程方式一：继承Thread类，重写run()方法，调用start开启线程

//总结：线程开启不是立即执行，由CPU调度。
public class TestThread1 extends Thread{
    @Override
    public void run() {
        //run方法线程体
        for (int i = 0; i < 20; i++) {
            System.out.println("我在看代码--"+i);
        }
    }

    public static void main(String[] args) {
        //main线程，主线程
        TestThread1 testThread1 = new TestThread1();

        //调用start方法开启线程
        testThread1.start();
        for (int i = 0; i < 20; i++) {
            System.out.println("我在学习多线程"+i);//同时进行，交替进行
        }
    }
}

实现Runnable接口

1、实现接口Runnable具有多线程能力

2、启动线程: 传入目标对象+Thread对象.start()

3、推荐使用:避免单继承局限性，灵活方便，方便同一个对象被多个线程使用

public class TestThread4 implements Runnable{

    //票数
    private int ticketNums = 10;
    @Override
    public void run() {
        while(true){
            if(ticketNums<=0){
                break;
            }
            System.out.println(Thread.currentThread().getName()+"拿到了第"+ticketNums--+"张票");
        }
    }
    public static void main(String[] args) {
        TestThread4 testThread4 = new TestThread4();
        new Thread(testThread4,"小明").start();
        new Thread(testThread4,"小王").start();
        new Thread(testThread4,"黄牛").start();
    }
}

public class TestThread5 implements  Runnable{
    private   String winner;

    @Override
    public void run() {
        for (int i = 0; i <=100; i++) {
            boolean falg= over(i);
            if(falg){
                break;
            }
            System.out.println(Thread.currentThread().getName()+"跑了"+i+"步");
        }
    }
    private boolean over(int step){
        if(winner!=null){
            return true;
        }
        if(step==100){
            winner = Thread.currentThread().getName();
            System.out.println("winner is"+winner);
            return true;
        }
        return false;
    }

    public static void main(String[] args) {
        TestThread5 testThread5 = new TestThread5();
        new Thread(testThread5,"兔子").start();
        new Thread(testThread5,"乌龟").start();
    }
}

实现Callable接口(了解即可)

1．实现Callable接口，需要返回值类型

2．重写call方法，需要抛出异常

3．创建目标对象

4．创建执行服务: ExecutorService ser = Executors.newFixedThreadPool(1);

5．提交执行:Future result1 = ser.submit(t1);

6．获取结果: boolean r1 = result1.get()

7．关闭服务: ser.shutdownNow();

//实现Callable接口
public class TestThread6 implements Callable {
    private String url;
    private String name;
  public  TestThread6(String url,String name){
      this.url=url;
      this.name=name;
  }
   //下载图片执行体
    @Override
    public Boolean call(){
        Webdownload webdownload = new Webdownload();
        webdownload.download(url,name);
        System.out.println("下载文件名为"+name);
        return true;
    }

    public static void main(String[] args) throws ExecutionException,InterruptedException {
        TestThread6 testThread1 = new TestThread6("https://cn.bing.com/","1.jpg");
        TestThread6 testThread2= new TestThread6("https://cn.bing.com/","2.jpg");
        TestThread6 testThread3 = new TestThread6("https://cn.bing.com/","3.jpg");

        //创建执行服务
        ExecutorService ser = Executors.newFixedThreadPool(3);

        //提交执行
        Future<Boolean> r1 = ser.submit(testThread1);
        Future<Boolean> r2 = ser.submit(testThread2);
        Future<Boolean> r3 = ser.submit(testThread3);

        //获取结果
        boolean rs1 = r1.get();
        boolean rs2 = r2.get();
        boolean rs3 = r3.get();

        //打印
        System.out.println(rs1);
        System.out.println(rs2);
        System.out.println(rs3);
        
        //关闭服务
        ser.shutdownNow();
    }
}