WorkUnit

// Implemented as a solution to the question in: http://stackoverflow.com/questions/13005964/thread-pool-where-workers-are-both-producers-and-consumers

public class WorkUnit implements Runnable, Comparable<WorkUnit> {

    // the maximum and actual time in ms this job will spend simulating processing
    private long maxJobTimeMS, processingTime;

    // an integer to specify the maximum number of other work units this one may spawn
    private int maxBranchingFactor;

    // an executor to schedule new jobs to
    private TestExecutor executor;

    public WorkUnit(long maxJobTimeMS, int maxBranchingFactor, TestExecutor executor) {
        this.maxJobTimeMS = maxJobTimeMS;
        this.maxBranchingFactor = maxBranchingFactor;
        this.executor = executor;
        this.processingTime = randomLong(this.maxJobTimeMS);
    }

    public void run() {
        // simulate some processing time
        try {
            Thread.sleep(this.processingTime);
            System.out.println(this.toString() + " took " + this.processingTime + "ms.");
        }
        catch(InterruptedException e) {
            if(executor.awaitCompletionTimedOut()) {
                terminateWork();
            }
        }

        // submit a random number of new jobs up to a maximum branching factor before completion
        int newJobCount = (int)randomLong(this.maxBranchingFactor);
        while(newJobCount-- > 0 && !executor.awaitCompletionTimedOut()) {
            long newWaitTime = randomLong(this.maxJobTimeMS);
            System.out.println(this.toString() + " generated a new job which will take: " + newWaitTime + "ms.");
            this.executor.executeJob(new WorkUnit(maxJobTimeMS, maxBranchingFactor, executor));
        }
    }

    private void terminateWork() {
        System.out.println(this.toString() + " has been interrupted and encountered a timeout; exiting...");
    }

    private long randomLong(long max) {
        return Math.round(Math.random() * (double)max);
    }

    public int compareTo(WorkUnit o) {
        if(this == o) {
            return 0;
        }
        // example job ordering: here, short jobs over longer ones
        return Long.compare(this.processingTime, o.processingTime);
    }
}