Cancelling a Callable implementation doesn't work correctly

Question

I began to immigrate to java thread pool instead of own my framework for pooling threads. So, I wrote a sample for this aim. Actually, the largest requirement is to stop the running thread if its execution is too late. In addition, to achieve this purpose, I use cancel method of Future class. In conclusion, the problem is the running thread after canceling it was not stopped and it's continuing to execute. My code is :

public class ThreadPoolWarmup
{
    static class CountDownClock1 implements Callable<Boolean>
    {
        public Boolean call() throws Exception
        {
            String threadName = Thread.currentThread().getName();
            long i = 0;
            for (; ; )
            {
                if ((i % 1000000000) == 0)
                    System.out.println(i + ", ");
                i++;
            }
        }
    }

    public static void main(String[] args)
    {
        Future<Boolean> f1 = null;
        try
        {
            ApplicationContext context = new ClassPathXmlApplicationContext("threadpool.xml");
            ThreadPoolTaskExecutor taskExecutor = (ThreadPoolTaskExecutor) context.getBean("taskExecutor");
            f1 = taskExecutor.submit(new CountDownClock1());
            Boolean b1 = f1.get(15,TimeUnit.SECONDS);
            System.out.println("Reslt is ===========>>>>> " +  b1);
        }
        catch (Exception t)
        {
            t.printStackTrace();
            boolean c1 = f1.cancel(true);
            System.out.println("Cancel result ======>>>>>>>>>  " + c1);
        }
    }
}

also the spring context (threadpool.xml) is:

<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:context="http://www.springframework.org/schema/context"
   xsi:schemaLocation="http://www.springframework.org/schema/beans
                       http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
                        http://www.springframework.org/schema/context
                        http://www.springframework.org/schema/context/spring-context-3.1.xsd">

<bean id="taskExecutor"  class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor">
    <property name="corePoolSize" value="3" />
    <property name="maxPoolSize" value="3" />
    <property name="WaitForTasksToCompleteOnShutdown" value="true" />
    <property name="queueCapacity" value="-1"/>
    <property name="keepAliveSeconds" value="30"/>
</bean>

and when I run the program I get following the rerult:

0, 
1000000000, 
2000000000, 
3000000000, 
4000000000, 
5000000000, 
java.util.concurrent.TimeoutException
    at java.util.concurrent.FutureTask.get(FutureTask.java:205)
    at thread.ThreadPoolWarmup.main(ThreadPoolWarmup.java:38)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
Cancel result ======>>>>>>>>>  true
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
6000000000, 
7000000000, 
8000000000, 
9000000000, 
10000000000, 
11000000000, 
12000000000, 
13000000000, 
14000000000, 

(I didn't write all output because it's continuing forever.)

I told you my problem and I have another question: When I cancel the thread and stop it, the thread return to the thread pool and another task can be executed by that?

Answer 1

Your task is simply uncancellable if already running, because the task doesn't perform anything to check whether the thread is interrupted.

If you make your loop into a while(!Thread.currentThread().isInterrupted()) the cancel(true) can try to interrupt the thread, which would then be noticed by the loop.

Using interruptible operations inside the task would also make it cancelable.