@FunctionalInterface
public interface Callable<V> {
  V call() throws Exception;
}

public class TestCallable {
  public static void main(String[] args) {
    CallableThreadDemo ctd = new CallableThreadDemo();
    //1.执行Callable方式，需要FutureTask实现类的支持，用于接收运算结果
    FutureTask<Integer> result = new FutureTask<Integer>(ctd);
    new Thread(result).start();
    //2.接收线程运算后的结果
    try {
      Integer sum = result.get(); //FutureTask 可用于闭锁
      System.out.println(sum);
    } catch (InterruptedException | ExecutionException e) {
      e.printStackTrace();
    }
  }
}
class CallableThreadDemo implements Callable<Integer>{
  @Override
  public Integer call() throws Exception {
    int sum = 0;
    for (int i = 0; i <= 100; i++) {
      sum += i;
    }
    return sum;
  }
}