多线程Callable使用

多线程情况下 使用callable的好处是 可以获取到结果

注意使用callable时 要结合 FutureTask使用，因为FutureTask类继承runnbale接口，Thread类实例化时必须要传runnable或其子类。FutureTask实例化时 要传callable类，所以callable和FutureTask要结合使用 

class CallableThread implements Callable{

  @Override
  public Integer call() throws Exception {
    System.out.println(Thread.currentThread().getName()+"  come in callable");
    TimeUnit.SECONDS.sleep(2);
    return 1024;
  }
}

class RunnableThread implements Runnable{
  @Override
  public void run() {
    System.out.println(Thread.currentThread().getName()+"  come in Runnable");
  }
}
public class CallableDemo {
  public static void main(String[] args) throws ExecutionException, InterruptedException {
    CallableThread callableThread = new CallableThread();
    FutureTask callableTask = new FutureTask<>(callableThread);
    new Thread(callableTask,"callableThread").start();
    System.out.println("before get result");
    Integer callableResult = callableTask.get();
    System.out.println("after get result");
    System.out.println("callableThread result:"+callableResult);

    RunnableThread runnableThread = new RunnableThread();
    FutureTask runnableTask =new FutureTask<>(runnableThread,1);
    new Thread(runnableTask,"runnableThread").start();
    Integer runnableResult = runnableTask.get();
    System.out.println("runnableThread result:"+runnableResult);
  }
}

结果

before get result
callableThread  come in callable
after get result
callableThread result:1024
runnableThread  come in Runnable
runnableThread result:1