实现多线程方式1：继承类Thread——重写方法run——调用方法start

从网络下载图片首先要增加包commons-io.jar

import org.apache.commons.io.FileUtils;
import java.io.File;
import java.io.IOException;
import java.net.URL;

/**
* 下载图片
*/

public class WebDownLoader {

/\*\*  
 \* 下载工具  
 \* @param url  
 \* @param name  
 \*/  
public void download(String url,String name){  
    try {  
        FileUtils.copyURLToFile(new URL(url),new File(name));  
    } catch (IOException e) {  
        e.printStackTrace();  
    }  
}

}

public class TDownloader extends Thread{
String url;
String name;

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

@Override  
public void run() {  
    WebDownLoader webDownLoader=new WebDownLoader();  
    webDownLoader.download(url,name);  
}

public static void main(String\[\] args) {  
    TDownloader t1=new TDownloader("http://pic28.nipic.com/20130424/3822951\_142421949000\_2.jpg","photo1.jpg");  
    TDownloader t2=new TDownloader("http://pic1.win4000.com/wallpaper/2018-01-23/5a669e431688c.jpg","photo2.jpg");  
    TDownloader t3=new TDownloader("http://pic1.win4000.com/wallpaper/6/57a2ea76bcc06.jpg","photo3.jpg");

    t1.start();  
    t2.start();  
    t3.start();  
}  

}

实现多线程方式2：实现Runnable——重写run()方法——new Thread( 实现了Runnable接口的对象 ).start

下载工具类和上面一样，实现多线程的类变了

public class TDownloader implements Runnable{
String url;
String name;

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

@Override  
public void run() {  
    WebDownLoader webDownLoader=new WebDownLoader();  
    webDownLoader.download(url,name);  
}

public static void main(String\[\] args) {  
    TDownloader t1=new TDownloader("http://pic28.nipic.com/20130424/3822951\_142421949000\_2.jpg","photo1.jpg");  
    TDownloader t2=new TDownloader("http://pic1.win4000.com/wallpaper/2018-01-23/5a669e431688c.jpg","photo2.jpg");  
    TDownloader t3=new TDownloader("http://pic1.win4000.com/wallpaper/6/57a2ea76bcc06.jpg","photo3.jpg");

    new Thread(t1).start();  
    new Thread(t2).start();  
    new Thread(t3).start();  
}  

}