java - 如何向线程传递参数并获取返回值？

Question

public class CalculationThread implements Runnable {

    int input;
    int output;

    public CalculationThread(int input)
    {
        this.input = input;
    }

    public void run() {
        output = input + 1;
    }

    public int getResult() {
        return output;
    }
}

其他地方:

Thread thread = new Thread(new CalculationThread(1));
thread.start();
int result = thread.getResult();

当然，thread.getResult() 不起作用(它尝试从 Thread 类调用此方法)。

你得到了我想要的。我怎样才能在Java中实现这一点？

Answer 1

这是线程池的工作。您需要创建一个 Callable<R>这是 Runnable返回一个值并将其发送到线程池。

此操作的结果是 Future<R>这是指向此作业的指针，它将包含计算值，或者如果作业失败则不会包含计算值。

public static class CalculationJob implements Callable<Integer> {
    int input;

    public CalculationJob(int input) {
        this.input = input;
    }

    @Override
    public Integer call() throws Exception {
        return input + 1;
    }
}

public static void main(String[] args) throws InterruptedException {
    ExecutorService executorService = Executors.newFixedThreadPool(4);

    Future<Integer> result = executorService.submit(new CalculationJob(3));

    try {
        Integer integer = result.get(10, TimeUnit.MILLISECONDS);
        System.out.println("result: " + integer);
    } catch (Exception e) {
        // interrupts if there is any possible error
        result.cancel(true);
    }

    executorService.shutdown();
    executorService.awaitTermination(1, TimeUnit.SECONDS);
}

打印:

result: 4