四、继承Thread类

步骤：

1. 自定义线程类继承Thread类
2. 重写run()方法，编写线程执行体
3. 创建线程对象，调用start()方法启动线程

//方式一：继承Thread类
public class Demo01 extends Thread{

    //主线程
    public static void main(String[] args) {

        Demo01 demo01 = new Demo01();
        demo01.start();

        for (int i = 0; i < 200; i++) {
            System.out.println("我是主线程："+i);
        }
    }


    @Override
    public void run() {
        for (int i = 0; i < 20; i++) {
            System.out.println("我是子线程："+i);
        }
    }
}

 

部分结果：可以看出来，两条线程交替执行。

 

 

练习：多线程同步下载网络图片

public class MyThread extends Thread{


    private String url;

    private String name;

    public MyThread(String url, String name) {
        this.url = url;
        this.name = name;
    }

    @Override
    public void run() {
        WebDownloader webDownloader = new WebDownloader();
        webDownloader.downloader(this.url,this.name);
    }


    public static void main(String[] args) {

        MyThread t1 = new MyThread("https://yjsc.gxu.edu.cn/images/2021-for100.jpg","1.jpg");
        MyThread t2 = new MyThread("https://yjsc.gxu.edu.cn/images/2022yjsy.jpg","2.jpg");
        MyThread t3 = new MyThread("https://yjsc.gxu.edu.cn/images/2022newyear.jpg","3.jpg");
        MyThread t4 = new MyThread("https://yjsc.gxu.edu.cn/images/202010banner.jpg","4.jpg");
        t1.start();
        t2.start();
        t3.start();
        t4.start();
    }

}


class WebDownloader{

    public void  downloader(String url, String name) {
        try {
            FileUtils.copyURLToFile(new URL(url),new File(name));
            System.out.println("图片："+name+"，下载完成");
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

}

结果：