如何从Callable()返回对象

Question

我试图从call()返回一个二维数组,我遇到了一些问题.到目前为止我的代码是:

//this is the end of main   
Thread t1 = new Thread(new ArrayMultiplication(Array1, Array2, length));
t1.start(); 
}

    public int[][] call(int[][] answer)
    {       

    int[][] answer = new int[length][length]; 

    answer = multiplyArray(Array1, Array2, length); //off to another function which returns the answer to here  

    return answer;                                  
    }

这段代码编译,这不是返回我的数组.我确定我可能使用了错误的语法,但我找不到任何好的例子.

编辑:改了一下

Answer 1

这里有一些代码演示了Callable <>接口的用法:

public class test {
public static void main(String[] args) throws ExecutionException, InterruptedException {
    Callable callable = new Callable() {
        @Override
        public int[][] call() throws Exception {
            int[][] array = new int[5][];
            for (int i = 0; i < array.length; i++) {
                array[i] = new int[]{5 * i, 5 * i + 1, 5 * i + 2, 5 * i + 3};
            }

            return array;
        }
    };

    ExecutorService service = Executors.newFixedThreadPool(2);
    Future<int[][]> result = service.submit(callable);

    int[][] intArray = result.get();
    for (int i = 0; i < intArray.length; i++) {
        System.out.println(Arrays.toString(intArray[i]));
    }
}
}

这样做是构造一个可以提交给执行者服务的对象.它与Runnable基本相同,只是它可以返回一个值; 我们在这里做的是创建一个带有两个线程的ExecutorService,然后将这个callable提交给服务.

接下来发生的事情是result.get(),它将阻塞直到callable返回.

你可能不应该自己做Thread管理.

Answer 2

添加到Joseph Ottinger的答案,要传递要在Callable的call()方法中使用的值,您可以使用闭包:

    public static Callable<Integer[][]> getMultiplierCallable(final int[][] xs,
            final int[][] ys, final int length) {
        return new Callable<Integer[][]>() {
            public Integer[][] call() throws Exception {
                Integer[][] answer = new Integer[length][length];
                answer = multiplyArray(xs, ys, length);
                return answer;
            }
        };
    }

    public static void main(final String[] args) throws ExecutionException,
            InterruptedException {
        final int[][] xs = {{1, 2}, {3, 4}};
        final int[][] ys = {{1, 2}, {3, 4}};
        final Callable<Integer[][]> callable = getMultiplierCallable(xs, ys, 2);
        final ExecutorService service = Executors.newFixedThreadPool(2);
        final Future<Integer[][]> result = service.submit(callable);
        final Integer[][] intArray = result.get();
        for (final Integer[] element : intArray) {
            System.out.println(Arrays.toString(element));
        }
    }