修复未来未检查的分配警告

Question

我有一个代码可以 ping 给定子网中的所有 IP 地址。它使用并发来提高性能，因为等待每个 IP 地址的超时将花费更长的时间：

/**
 * @param subNetwork The subnet to scan
 * @return A list of internet protocol addresses that are reachable
 * @throws IOException
 * @throws ExecutionException
 * @throws InterruptedException
 */
public static List<String> getRespondingInternetProtocolAddresses(final String subNetwork) throws IOException,
        ExecutionException,
        InterruptedException
{
    final List<String> activeInternetProtocolAddresses = new ArrayList<>();
    int startingIndex = 1;
    int upperBound = 256;
    int poolSize = upperBound - 1; // Query concurrently for best time savings
    ExecutorService threadPool = Executors.newFixedThreadPool(poolSize);
    List<Future<Runnable>> tasks = new ArrayList<>();

    for (int currentSubNetIndex = startingIndex; currentSubNetIndex < upperBound;
         currentSubNetIndex++)
    {
        final int subNetIndex = currentSubNetIndex;

        // Query each Internet protocol address concurrently for speed purposes
        Future task = threadPool.submit(new Thread(() ->
        {
            String currentInternetProtocolAddress = subNetwork + "." + subNetIndex;

            try
            {
                if (Ping.isReachable(currentInternetProtocolAddress))
                {
                    activeInternetProtocolAddresses.add(currentInternetProtocolAddress);
                }
            } catch (IOException exception)
            {
                exception.printStackTrace();
            }
        }));

        tasks.add(task); // TODO Fix unchecked assignment warning
    }

    for (Future<Runnable> task : tasks)
    {
        task.get();
    }

    threadPool.shutdown();

    return activeInternetProtocolAddresses;
}

在任务列表中添加新任务时，我收到了未经检查的分配警告：

tasks.add(task);

我尝试将 Future by replacing it with Future<Runnable> but it created a compile error instead since submit() returns 泛化为 Future<?>。

我该怎么做才能修复警告？

Answer 1

Future<T> 在应从任务返回类型 T 的某些结果时使用 - 然后您将获得此结果并使用它。

如果您只需要等到所有任务执行完毕，请使用 threadPool.submit(Runnable r)。然后在 threadPool.shutdown() 调用 threadPool.awaitTermination() 之后——阻塞直到所有任务完成。

Answer 2

要解决此问题，您可以将任务声明为 List<Future<?>> 并将 task 声明为 Future<?>。

修复未来未检查的分配警告

Fix Future Unchecked Assignment Warning

java

concurrency

future

executorservice