如何从另一个线程的方法获得结果

Question

我在Otherclass类中有方法test(),它返回String结果:

public class Otherclass {
    int i = 0;

    public String test()
    {       
        Thread t = new Thread(new Runnable() {

            @Override
            public void run() {
                 System.out.println("GoToThread");
                 while(i < 10) {
                    i++;
                    System.out.println("value "+i);
                    try {
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }                   
                }
            }               
        });
        t.start();

        String result = "result value i = "+i;

        return result;
    }
}

我从主类调用此方法

Otherclass oc = new Otherclass();
System.out.println(oc.test());

并希望得到结果为result value i = 10 但是在返回methos结果后运行Otherclass中的线程,我得到的结果如下:

result value i = 0
GoToThread
value1
value 2
value 3
value 4
value 5
value 6
value 7
value 8
value 9
value 10

请帮忙,运行Thread后我可以通过哪些方法获得test()方法的结果？

Answer 1

修复你的代码

你需要等待你的t线程完成使用join():

t.start();
t.join(); // this makes the main thread wait for t to finish
String result = "result value i = "+i;

另外一个选项

Callable如果需要从线程返回值,请考虑实现.例如:

public static void main(String[] args) throws Exception {

  Callable<Integer> worker = new Callable<Integer>() {
    @Override
    public Integer call() throws Exception {
      Integer i = 0;

      while (i < 10) {
        i++;
        System.out.println("value " + i);
        Thread.sleep(500);
      }

      return i;
    }
  };

  Future<Integer> result = Executors.newSingleThreadExecutor().submit(worker);
  System.out.println(result.get());
}

输出是:

value 1
value 2
value 3
value 4
value 5
value 6
value 7
value 8
value 9
value 10
10