多线程day1：继承Thread类和实现Runnable接口来实现多线程

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单一继承局限性

public class TestThread1 extends Thread {
    @Override
    public void run() {
        for (int i = 0; i < 200; i++) {
            System.out.println("我在写代码~~~"+i);
        }
    }

    public static void main(String[] args) {
        TestThread1 testThread1 = new TestThread1();
            testThread1.start();

        for (int i = 0; i < 1000; i++) {
            System.out.println("我在看学习视频~~~"+i);
        }
    }
}```

**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：避免单一继承局限性，灵活方便，方便同一个对象被多个线程使用

```java
public class TestThread3 implements Runnable {
    @Override
    public void run() {
        for (int i = 0; i < 200; i++) {
            System.out.println("我在搞学习~~！");
        }
    }

    public static void main(String[] args) {
        TestThread3 testThread3 = new TestThread3();

        Thread thread = new Thread(testThread3);
        thread.start();
        for (int i = 0; i < 1000; i++) {
            System.out.println("我在写代码~~~~~~！");
        }

    }
}

从网页上面下载图片的代码，实现Runnable接口完成，代码如下

public class Thread2 implements Runnable {
    private String url;//网络图片地址
    private String name;//保存的文件名
    public Thread2(String url,String name){
        this.url=url;
        this.name=name;
    }
    @Override
    public void run() {
        WebDownloader webDownloader = new WebDownloader();
        webDownloader.downloader(url,name);
        System.out.println("下载了图片："+name);
    }

    public static void main(String[] args) {
        Thread2 t1 = new Thread2("https://img2018.cnblogs.com/blog/1309478/201905/1309478-20190512183209781-282460662.png","1.jpg");
        Thread2 t2 = new Thread2("https://img2018.cnblogs.com/blog/1309478/201905/1309478-20190512183435353-1154033226.png","2.jpg");
        Thread2 t3 = new Thread2("https://img2018.cnblogs.com/blog/1309478/201905/1309478-20190512183346178-713966030.png","3.jpg");
        //同时执行，不是按顺序下载
        new Thread(t1).start();
        new Thread(t2).start();
        new Thread(t3).start();
    }
}
//下载器
class WebDownloader{
    //下载方法
    public void downloader(String url,String name){
        try {
            FileUtils.copyURLToFile(new URL(url),new File(name));
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("IO异常，downloader方法出现问题");
        }
    }
}