未来的任务抛出由 IndexOutOfBoundsException 引起的 ExecutionException，而据我所知，我没有使用数组

Question

以下代码段：

public void handleInput() {
        Scanner sc = new Scanner(System.in);
        int x = 3;

        while (true) {

            FutureTask<String> readNextLine = new FutureTask<String>(sc::nextLine);

            ExecutorService executor = Executors.newFixedThreadPool(10);
            executor.execute(readNextLine);

            try {
                String line = readNextLine.get(x * 1000, TimeUnit.MILLISECONDS);

            } catch (TimeoutException e) {
                System.out.println("timed out");
            } catch (ExecutionException | InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

将输出 "timed out" 两次，这是预期的，但之后它将循环抛出 ExecutionException，堆栈如下

java.util.concurrent.ExecutionException: java.lang.IndexOutOfBoundsException: end
    at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
    at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:205)
    at traceCalls.Trace.handleInput(Trace.java:32)
    at main.main(main.java:11)
Caused by: java.lang.IndexOutOfBoundsException: end
    at java.base/java.util.regex.Matcher.region(Matcher.java:1515)
    at java.base/java.util.Scanner.findPatternInBuffer(Scanner.java:1089)
    at java.base/java.util.Scanner.findWithinHorizon(Scanner.java:1791)
    at java.base/java.util.Scanner.nextLine(Scanner.java:1649)
    at java.base/java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:264)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at java.base/java.lang.Thread.run(Thread.java:834)

显然我做错了一些事情，但我不知道是什么。

Answer 1

扫描器 class 不是线程安全的，正如它的 javadoc 所说：

A Scanner is not safe for multithreaded use without external synchronization.

因此，如果您真的想在多个线程中读取 System.in（很可能您不需要！），您需要为每个线程创建扫描器，或使用同步。

未来的任务抛出由 IndexOutOfBoundsException 引起的 ExecutionException，而据我所知，我没有使用数组

Future task throws ExecutionException caused by IndexOutOfBoundsExceptionwhile I, to the best of my knowledge am using no array

java

futuretask

executionexception