Example thread pool manager in java

ThreadPoolWorkHandler.java

package com.jbirdvegas.testing;

import java.util.List;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class ThreadPoolWorkHandler {

    private static final int QUEUE_SIZE = 50;
    private static final int NUMBER_OF_THREADS_WHEN_IDLE = 3;
    private static final int MAX_THREADS_IN_POOL = 8;
    private static final long IDLE_THREAD_LIVES_AFTER_WHEN_NO_WORK = 30;
    private static ThreadPoolWorkHandler sInstance;
    private final ArrayBlockingQueue<Runnable> mQueue;
    private final ThreadPoolExecutor mThreadPool;

    private ThreadPoolWorkHandler() {
        mQueue = new ArrayBlockingQueue<>(QUEUE_SIZE);
        mThreadPool = new ThreadPoolExecutor(NUMBER_OF_THREADS_WHEN_IDLE,
                MAX_THREADS_IN_POOL,
                IDLE_THREAD_LIVES_AFTER_WHEN_NO_WORK,
                TimeUnit.SECONDS,
                mQueue);
    }

    public static ThreadPoolWorkHandler getInstance() {
        if (sInstance == null) {
            sInstance = new ThreadPoolWorkHandler();
        }
        return sInstance;
    }

    public void submitWork(Runnable work) {
        mQueue.add(work);
    }

    /**
     * Shuts down the threads when all submitted work is complete
     */
    public void orderlyShutdown() {
        mThreadPool.shutdown();
    }

    /**
     * Does not wait for all submitted work to be complete before shutting down
     *
     * @return work that was awaiting processing
     */
    public List<Runnable> shutdownNow() {
        return mThreadPool.shutdownNow();
    }
}