创建线程的三种方式

1、继承Thread类，重写run方法，调用start方法启动线程；

package Thread;

//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：注意，线程开启不一定立即执行，由CPU调度执行
public class threadDemo1 extends Thread {
    @Override
    public void run() {
        //run方法线程体
        for (int i = 0; i < 5; i++) {
            System.out.println("我在看代码---"+i);

        }
    }

    public static void main(String[] args) {
        //main线程，主线程
        //创建一个线程对象
        threadDemo1 threadDemo1 = new threadDemo1();
        //调用start()方法开启线程
        threadDemo1.start();

        for (int i = 0; i < 1000; i++) {
            System.out.println("我在学习"+i);
        }
    }
}　　

结果：

 2、实现Runnable方法，重写run方法，执行线程需要丢入runable接口实现类，启动调用start方法；

package Thread;
//创建线程方法2：实现runnable接口，重写run方法，执行线程需要丢入runnable接口实现类，调用start方法
public class threadDemo3 implements Runnable {
    @Override
    public void run() {
        //run方法线程体
        for (int i = 0; i < 5; i++) {
            System.out.println("我在看代码---"+i);

        }
    }
    public static void main(String[] args) {
        //创建runnable接口的实现类对象
        threadDemo3 threadDemo3 = new threadDemo3();
        //调用start()方法开启线程
        Thread thread = new Thread(threadDemo3);
        thread.start();

        for (int i = 0; i < 1000; i++) {
            System.out.println("我在学习"+i);
        }
    }
}

3、实现Callable接口；

package Thread;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.*;

//线程创建方式三：实现Callable接口

/**
 * callable的好处：
 * 1、可以定义返回值
 * 2、可以抛出异常
 */
public class TestCallable implements Callable<Boolean> {
    private String url;//网络图片地址
    private String name;//保存的文件名

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

    @Override
    public Boolean call() {
        WebDownloader webDownloader = new WebDownloader();
        webDownloader.downloader(url,name);
        System.out.println("下载了文件名为："+name+"的文件");
        return true;
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        TestCallable t1 = new TestCallable("http://img.tuguaishou.com/ips_templ_preview/w432_q100/c5/f6/a7/lg_2559370_1572354908_5db83b5c038ec.jpg?auth_key=2239632000-0-0-6c120c2d0677dc637cb897b4e030d240", "1.jpg");
        TestCallable t2 = new TestCallable("http://img.tuguaishou.com/ips_templ_preview/w432_q100/f9/15/19/lg_3402655_1603039421_5f8c70bd859a6.jpg?auth_key=2239632000-0-0-12b2428b47e0b0163ba832a29b2a3951", "2.jpg");
        TestCallable t3 = new TestCallable("http://img.tuguaishou.com/ips_templ_preview/w432_q100/c5/f6/a7/lg_2559370_1572354908_5db83b5c038ec.jpg?auth_key=2239632000-0-0-6c120c2d0677dc637cb897b4e030d240", "3.jpg");

        //1、创建执行服务 3个
        ExecutorService ser = Executors.newFixedThreadPool(3);
        //2、提交执行
        Future<Boolean> r1 = ser.submit(t1);
        Future<Boolean> r2 = ser.submit(t2);
        Future<Boolean> r3 = ser.submit(t3);
        //3、获取结果
        boolean rs1 = r1.get();
        boolean rs2 = r2.get();
        boolean rs3 = r3.get();
        //4、关闭服务
        ser.shutdownNow();
    }
}
//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！");
        }
    }
}