三种

1. Thread class :继承Thread类
2. Runnable 接口：实现Runnable接口、
3. Callable接口：实现Callable接口

Thread

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

package com.kai.lesson1;
public class TestThread1 extends Thread{
    @Override
    public void run() {
        for (int i=0;i<20;i++){
            System.out.println("rum方法");
        }
    }
    public static void main(String[] args) {
        //main线程，主线程
        TestThread1 testThread1=new TestThread1();
        testThread1.start();
        for (int i=0;i<20000;i++){
            System.out.println("主线程");
        }
    }
}

1. 线程开启不一定立即执行，由CPU安排调度

例子

package com.kai.lesson1;
//联系Thread,实现多线程同步下载图片
import org.apache.commons.io.FileUtils;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
public class TestThread2 extends Thread{
    private String url;
    private String name;
    public TestThread2(String url, String name){
        this.url=url;
        this.name=name;
    }
    @Override
    public void run() {
        WebDownloader webDownloader=new WebDownloader();
        try {
            webDownloader.dowanloader(url,name);
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println("下载了文件名为:"+name);
    }
    public static void main(String[] args) {
        TestThread2 t1=new TestThread2("http://i0.hdslb.com/bfs/bangumi/image/86fdce81522f76b8b323776c7c77f044e13fc808.png","2.jpg");
        TestThread2 t2=new TestThread2("http://i0.hdslb.com/bfs/bangumi/image/86fdce81522f76b8b323776c7c77f044e13fc808.png","3.jpg");
        TestThread2 t3=new TestThread2("http://i0.hdslb.com/bfs/bangumi/image/86fdce81522f76b8b323776c7c77f044e13fc808.png","4.jpg");
        t1.start();
        t2.start();
        t3.start();
    }
}
//下载器
class WebDownloader{
    //下载方法
    public void dowanloader(String url, String name) throws IOException {
        try {
            FileUtils.copyURLToFile(new URL(url),new File(name));
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("IOy异常，downloader方法出现问题");
        }
    }
}

Runnable

创建线程方式：

1. 实现runnable接口
2. 重写run方法
3. 执行线程需要丢入runnable接口实现类，调用start方法

package com.kai.lesson1;
public class TestThread3 implements Runnable {
    @Override
    public void run() {
        for (int i=0;i<20;i++){
            System.out.println("rum方法");
        }
    }
    public static void main(String[] args) {
        //创建runnable接口实现类对象
        TestThread3 testThread3=new TestThread3();
        //创建线程对象，通过线程对象开启线程，代理
        //Thread thread=new Thread(testThread3);
        //thread.start();
        new Thread(testThread3).start();
        for (int i=0;i<20000;i++){
            System.out.println("主线程");
        }
    }
}

例子

package com.kai.lesson1;
//联系Thread,实现多线程同步下载图片
import org.apache.commons.io.FileUtils;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
public class TestThread2 implements Runnable{
    private String url;
    private String name;
    public TestThread2(String url, String name){
        this.url=url;
        this.name=name;
    }
    @Override
    public void run() {
        WebDownloader webDownloader=new WebDownloader();
        try {
            webDownloader.dowanloader(url,name);
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println("下载了文件名为:"+name);
    }
    public static void main(String[] args) {
        TestThread2 t1=new TestThread2("http://i0.hdslb.com/bfs/bangumi/image/86fdce81522f76b8b323776c7c77f044e13fc808.png","22.jpg");
        TestThread2 t2=new TestThread2("http://i0.hdslb.com/bfs/bangumi/image/86fdce81522f76b8b323776c7c77f044e13fc808.png","33.jpg");
        TestThread2 t3=new TestThread2("http://i0.hdslb.com/bfs/bangumi/image/86fdce81522f76b8b323776c7c77f044e13fc808.png","44.jpg");
        /*
        t1.start();
        t2.start();
        t3.start();
         */
        new  Thread(t1).start();
        new  Thread(t2).start();
        new  Thread(t3).start();
    }
}
//下载器
class WebDownloader{
    //下载方法
    public void dowanloader(String url, String name) throws IOException {
        try {
            FileUtils.copyURLToFile(new URL(url),new File(name));
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("IOy异常，downloader方法出现问题");
        }
    }
}

总结