Getting error FutureTask@2c7b84de rejected when using threadpool

Question

Here is my code:

class Processor implements Runnable {

    private int id;
    private Integer interaction;
    private Set<Integer> subset;
    private static volatile AtomicBoolean notRemoved = new AtomicBoolean(true);

    public Object<E> dcp;
    public Iterator<Integer> iterator;



    public Processor(int id, Integer interaction, Set<Integer> subset, Object<E> dcp, Iterator<Integer> iterator) {
        this.id = id;
        this.interaction = interaction;
        this.subset= subset;
        this.dcp = dcp;
        this.iterator = iterator;
    }

    public void run() {
        while (Processor.notRemoved.get()){
            System.out.println("Starting: " + this.id);
            if (this.dcp.PA.contains(this.interaction)){
                this.subset.add(this.interaction);
                this.dcp.increaseScore(this.subset);
                if (!this.subset.contains(this.interaction) && Processor.notRemoved.get()){
                    Processor.notRemoved.set(false);
                    iterator.remove();
                }
            }

            System.out.println("Completed: " + this.id);
        }   
    }
}


public class ConcurrentApp {

    public void mainFunction (Object<E> dcp, int threads) {

        ExecutorService executor = Executors.newFixedThreadPool(threads);

        int i =1;
        while ((dcp.PA.size() > i) && (i <= dcp.R)){
            for (Iterator<Integer> iterator = dcp.PA.iterator(); iterator.hasNext();){
                Integer interaction = iterator.next();
                ArrayList<Integer> removed = new ArrayList<Integer>(dcp.PA);
                removed.remove(interaction);
                ArrayList<Set<Integer>> subsets = dcp.getSubsets(removed, i);
                for (int j = 0; j< subsets.size(); j++){
                    executor.submit(new Processor(j, interaction, subsets.get(j), dcp, iterator));
                }
                executor.shutdown();
                System.out.println("All tasks submitted");
                try {
                    executor.awaitTermination(1, TimeUnit.DAYS);
                } catch (InterruptedException e) {
                    System.out.println("HERE");
                    e.printStackTrace();
                }
            }
            System.out.println("All tasks completed");
            i++;
        }   
    }
}

When I run mainFunction in ConcurrentApp, I get the following error: Exception in thread "main" java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.FutureTask@2c7b84de rejected from java.util.concurrent.ThreadPoolExecutor@3fee733d[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 8]

I know this is because I'm not using executor.shutdown() correctly but I'm not sure why?

EDIT: I print when each thread starts and completes its task. Here is the console output:

Starting: 1
Starting: 2
All tasks submitted
Starting: 0
Completed: 2
Completed: 1
Completed: 0
Exception in thread "main" java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.FutureTask@2c7b84de rejected from java.util.concurrent.ThreadPoolExecutor@3fee733d[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 8]

This at least shows that the 3 threads in the thread pool complete their task before the error goes off.

Answer 1

I figured out the problem here! It was simply because I was calling executor.shutdown() within the while loop before all the tasks were completed. So the new code is:

    public void multiRemoveParents (DirectCausalPredictor<BayesianScoresNew> dcp, int threads) {

        ExecutorService executor = Executors.newFixedThreadPool(threads);

        int i =1;
        while ((dcp.PA.size() > i) && (i <= dcp.R)){
            for (Iterator<Integer> iterator = dcp.PA.iterator(); iterator.hasNext();){
                Integer interaction = iterator.next();
                ArrayList<Integer> removed = new ArrayList<Integer>(dcp.PA);
                removed.remove(interaction);
                ArrayList<Set<Integer>> subsets = dcp.getSubsets(removed, i);
                for (int j = 0; j< subsets.size(); j++){
                    try {
                        executor.submit(new Processor(j, interaction, subsets.get(j), dcp, iterator));
                    } catch (RejectedExecutionException e){
                        System.out.println("Task was rejected");
                    }   
                }
            }
            System.out.println("All tasks completed");
            i++;
        }
        executor.shutdown();
        System.out.println("All tasks submitted");
        try {
            executor.awaitTermination(1, TimeUnit.DAYS);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }