Ytukyg

I've a requirement to start and stop task from java application. I'm trying to use
ExecutorService to create threads and ExecutorCompletionService to check
processing status of thread . Startup and stop is a continious activity so in my
test code I've created a while loop .

public class ProcessController {



String processArray = { "Process1", "Process2", "Process3", "Process4", "Process5", "Process6", "Process7"      };

private List<String> processList = Arrays.asList(processArray);



public static void main(String args ) {



    ExecutorService startUpExecutor = Executors.newFixedThreadPool(3);

    ExecutorService cleanUpExecutor = Executors.newFixedThreadPool(3);



    CompletionService<String> startUpCompletionService = new ExecutorCompletionService<>(startUpExecutor);

    CompletionService<String> cleanUpCompletionService = new ExecutorCompletionService<>(cleanUpExecutor);



    List<Future<String>> cleanupFutures = new ArrayList<Future<String>>();

    List<Future<String>> startupFutures = new ArrayList<Future<String>>();



    ProcessController myApp = new ProcessController();



    int i = 0;



    while (i++ < 3) {

        System.out.println("**********Starting Iteration " + i + "************* =====> ");



        if (!cleanupFutures.isEmpty())   cleanupFutures.clear();





        myApp.processList.forEach(process -> cleanupFutures.add(cleanUpCompletionService.submit(new CleanupTask(process))));

        myApp.processList.forEach(process -> startupFutures.add(startUpCompletionService.submit(new StartupTask(process))));





        for (Future<String> f : cleanupFutures) {

            try {

                String result = cleanUpCompletionService.take().get();

                System.out.println("Result from  Cleanup thread : " + result);

            } catch (InterruptedException e) {

                e.printStackTrace();

            } catch (ExecutionException e) {

                e.printStackTrace();

            }

        }



            for (Future<String> f1 : startupFutures) {

                try {

                    String result = startUpCompletionService.take().get();

                    System.out.println("Result from  startup thread : " + result);

                } catch (InterruptedException e) {

                    e.printStackTrace();

                } catch (ExecutionException e) {

                    e.printStackTrace();

                }



            }

            System.out.println("**********Finished Iteration " + i + "************* =====> ");



        }



        startUpExecutor.shutdown();

       cleanUpExecutor.shutdown();

    }

}

CleanupTask class

public class CleanupTask implements Callable<String> {

private String task;



public CleanupTask(String task) {

    this.task = task;

}

@Override

public String call() throws Exception {

    checkIfAnyFinished();

    return "finished clean up processing for " + getThreadId();

}



private void checkIfAnyFinished( )

{

    System.out.println( getThreadId() + " Checking if task   " + this.task + " is finished");

    try {

        isFinished();

    } catch (InterruptedException e) {

        e.printStackTrace();

    }

}



private void isFinished() throws InterruptedException {

    Thread.sleep(1000*4);

}



private String getThreadId()

{

    return Thread.currentThread().getName();

}

}

Startup Task class

public class StartupTask implements   Callable<String> {



private String processSchedule ;



public StartupTask(String processSchedule) {

    this.processSchedule = processSchedule;

}



@Override

public String call() {

    scheduleifdue();

    return "finished start up up processing for " + getThreadId();

}



private void scheduleifdue()

{

    System.out.println(getThreadId() + " Checking " + this.processSchedule  + "  is due or not");

    try {

        Thread.sleep(4000);

    } catch (InterruptedException e) {

        e.printStackTrace();

    }

}

private String getThreadId()

{

    return Thread.currentThread().getName();

}

}

Above code successfully complete iteration 1 and start 2nd iteration . But it never finish and keeps running.

When I run the same application only with one task( either cleanup or startup) then it run without any issues. I'm not sure what is causing issue.