future.cancel不起作用

Question

我有一个漂亮而紧凑的代码,它不能像我预期的那样工作.

public class Test {

    public static void main(String[] args) {

        Runnable r = new Runnable() {
            @Override
            public void run() {
                try {
                    for (;;) {

                    }
                } finally {
                    System.out.println("FINALLY");
                }

            }
        };

        ExecutorService executor = Executors.newSingleThreadExecutor();

        Future<?> future = executor.submit(r);
        try {
            future.get(3, TimeUnit.SECONDS);
        } catch (TimeoutException e) {
            boolean c = future.cancel(true);
            System.out.println("Timeout " + c);
        } catch (InterruptedException | ExecutionException e) {
            System.out.println("interrupted");
        }
        System.out.println("END");

    }

}

输出是:

超时是真的

结束

问题:为什么不终止future.cancel(true)方法调用Runnable？程序将"END"写入输出后,"r"Runnable仍在运行.

Answer 1

问题是你的Runnable是不可中断的:任务中断是Java中的协作过程,如果被取消的代码被取消,它需要定期检查,否则它将不会响应中断.

您可以按如下方式修改代码,它应该按预期工作:

Runnable r = new Runnable() {
    @Override public void run() {
        try {
            while (!Thread.currentThread.isInterrupted()) {}
        } finally {
            System.out.println("FINALLY");
        }
    }
};