实现Callable接口

实现Callable接口

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 result1 = ser.submit(t1);
6. 获取结果：boolean r1 = result1.get()
7. 关闭服务：ser.shutdownNow();

• 使用Callable来改写图片下载项目

  //使用Callable来改写图片下载项目
  public class CallableTest implements Callable<Boolean> {
      private String url;   //网络地址
      private String name;  //文件名
  
      public CallableTest(String url,String name){
          this.url = url;
          this.name = name;
      }
  
      //下载图片的执行体
      @Override
      public Boolean call() {
          WebDownLoad webDownLoad = new WebDownLoad();
          webDownLoad.downLoad(url,name);
          System.out.println("文件名："+name);
          return true;
      }
  
      //练习：Thread ,实现多线程下载图片
      public static void main(String[] args) throws Exception{
          CallableTest th1 = new CallableTest("https://img.yalayi.net/d/file/2020/07/24/b6c4ac6b58124d7ac70344ea4992ab5d.jpg","xg1.jpg");
          CallableTest th2 = new CallableTest("https://img.yalayi.net/d/file/2020/06/22/13c501bca19b48eb558b4147493330f4.jpg","xg2.jpg");
          CallableTest th3 = new CallableTest("https://img.yalayi.net/d/file/2020/06/22/f49a10d2884df025bba6ced8e50cfa2f.jpg","xg3.jpg");
          //下载次序每次都会不同
          //创建执行服务 开启线程池:3为线程池数量
          ExecutorService ser= Executors.newFixedThreadPool(3);
          //提交执行
          Future<Boolean> future1=ser.submit(th1);
          Future<Boolean> future2=ser.submit(th2);
          Future<Boolean> future3=ser.submit(th3);
          //获取结果
          boolean flag1= future1.get();
          boolean flag2= future2.get();
          boolean flag3= future2.get();
          System.out.println(flag1);
          System.out.println(flag2);
          System.out.println(flag3);
          //关闭服务
          ser.shutdownNow();
      }
  }
  
  class WebDownLoad{
      //下载方法
      public void downLoad(String url,String name){
          try {
              FileUtils.copyURLToFile(new URL(url),new File(name));
          } catch (IOException e) {
              e.printStackTrace();
              System.out.println("IO异常，downLoad方法");
          }
      }
  }