如何创建线程

╰半夏微凉° 2023-10-01 21:25 12阅读 0赞

## 一、Thread ##

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（使线程进入就绪态）

也可以直接new一个Thread对象，在run方法中编写执行体，然后.start()启动线程

public class Thread1 extends Thread{
        //run方法线程体
        @Override
        public void run(){
            for (int i = 0; i < 20; i++) {
                System.out.println("你好"+i);
            }
        }
        //main线程，主线程
        public static void main(String[] args) {
            Thread1 t1 = new Thread1();
            t1.start();
            for (int i = 0; i < 20; i++) {
                System.out.println("我不好"+i);
            }
            Thread t2 = new Thread(){
                public void run(){
                    for (int i = 0; i < 20; i++) {
                        System.out.println("别吵了"+i);
                    }
                }
            };
            t2.start();
        }
    }

线程开启不一定执行，由CPU调度执行

示例：图片下载[多线程下载图片\_crazyK.的博客-CSDN博客][crazyK._-CSDN]

## 二、Runnable ##

1.创建一个类实现Runnable接口

2.实现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

public class TestThread1 implements Runnable{
        //run方法线程体
        @Override
        public void run(){
            for (int i = 0; i < 20; i++) {
                System.out.println("你好"+i);
            }
        }
        //main线程，主线程
        public static void main(String[] args) {
            //创建Runnable接口的实现类对象
            TestThread1 t1 = new TestThread1();
            //创建线程对象，通过线程对象开启线程，代理
            Thread t2 = new Thread(t1);
            t2.start();
            //也可以简写为 new Thread(t1).start()
            for (int i = 0; i < 20; i++) {
                System.out.println("我不好"+i);
            }
        }
    }

示例：龟兔赛跑[使用Runnable实现龟兔赛跑\_crazyK.的博客-CSDN博客][Runnable_crazyK._-CSDN]

## 三、Callable ##

1.实现Callable接口，需要返回值类型

2.重写call方法，需要抛出异常

3.创建目标对象

4.创建执行任务：ExecutorService ser = Executors.newFixedThreadPool(1);

ExecutorService ser = Executors.newFixedThreadPool(1);

5.提交执行：Future<Boolean> result1 = ser.submit(t1);

6.获取结果：boolean r1 = result1.get();

7.关闭服务：ser.shutdownNow();

这里的示例是根据多线程下载图片改写的[多线程下载图片\_crazyK.的博客-CSDN博客][crazyK._-CSDN 1]

public class TestCllable implements Callable<Boolean> {
        //图片地址
        private String url;
        //文件名
        private String name;
    
        public TestCllable(String url, String name){
            this.url = url;
            this.name = name;
        }
    
        @SneakyThrows
        @Override
        public Boolean call(){
            WebDownloader1 webDownloader = new WebDownloader1();
            webDownloader.downloader(url,name);
            System.out.println("下载了文件名为："+name);
            return true;
        }
    
        public static void main(String[] args) throws ExecutionException, InterruptedException {
            TestCllable t1 = new TestCllable("https://img2.baidu.com/it/u=1814268193,3619863984&fm=253&fmt=auto&app=138&f=JPEG?w=632&h=500","1.jpg");
            TestCllable t2 = new TestCllable("https://img2.baidu.com/it/u=957523443,3301463541&fm=253&fmt=auto&app=138&f=JPEG?w=700&h=497","2.jpg");
            TestCllable t3 = new TestCllable("https://img1.baidu.com/it/u=2306413288,4195946486&fm=253&fmt=auto&app=120&f=JPEG?w=680&h=655","3.jpg");
            //创建执行任务
            ExecutorService ser = Executors.newFixedThreadPool(3);
            //提交执行
            Future<Boolean> result1 = ser.submit(t1);
            Future<Boolean> result2 = ser.submit(t2);
            Future<Boolean> result3 = ser.submit(t3);
            //获取结果
            boolean r1 = result1.get();
            boolean r2 = result2.get();
            boolean r3 = result3.get();
            //关闭服务
            ser.shutdownNow();
        }
    }
    //下载器
    class WebDownloader{
        //下载方法
        public void downloader(String url,String name) throws IOException {
            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");
            }
        }
    }

Callable的好处：可以定义返回值，可以抛出异常，但是想对较为麻烦

[crazyK._-CSDN]: https://blog.csdn.net/weixin_57504474/article/details/123913153?spm=1001.2014.3001.5502
[Runnable_crazyK._-CSDN]: https://blog.csdn.net/weixin_57504474/article/details/123917567
[crazyK._-CSDN 1]: https://blog.csdn.net/weixin_57504474/article/details/123913153