九、实现Callable接口（了解即可）

步骤：

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. 创建执行服务: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();

 

改造同步下载网络图片：

public class CallableThread implements Callable {       private String url;      private String name;      public CallableThread(String url, String name) {         this.url = url;         this.name = name;     }      @Override     public Boolean call() throws Exception {         WebDownloader webDownloader = new WebDownloader();         webDownloader.downloader(this.url,this.name);         return true;     }      public static void main(String[] args) throws ExecutionException, InterruptedException {          CallableThread t1 = new CallableThread(https://yjsc.gxu.edu.cn/images/2021-for100.jpg,./callable/1.jpg);         CallableThread t2 = new CallableThread(https://yjsc.gxu.edu.cn/images/2022yjsy.jpg,./callable/2.jpg);         CallableThread t3 = new CallableThread(https://yjsc.gxu.edu.cn/images/2022newyear.jpg,./callable/3.jpg);         CallableThread t4 = new CallableThread(https://yjsc.gxu.edu.cn/images/202010banner.jpg,./callable/4.jpg);          ExecutorService service = Executors.newFixedThreadPool(4);          Future<Boolean> f1 = service.submit(t1);         Future<Boolean> f2 = service.submit(t2);         Future<Boolean> f3 = service.submit(t3);         Future<Boolean> f4 = service.submit(t4);          Boolean rs1 = f1.get();         Boolean rs2 = f2.get();         Boolean rs3 = f3.get();         Boolean rs4 = f4.get();         service.shutdownNow();     }   }   class WebDownloader{      public void  downloader(String url, String name) {         try {             FileUtils.copyURLToFile(new URL(url),new File(name));             System.out.println(图片：+name+，下载完成);         } catch (IOException e) {             throw new RuntimeException(e);         }     }  }