A simple thread pool in Java

ThreadPool.java

package org.tthew.core;

import java.util.ArrayDeque;
import java.util.Queue;

public final class ThreadPool
{
	public interface IThreadPool
	{
		void submitJob(final IJob job);
	}

	public interface IJob
	{
		void onThrowable(Throwable t);

		void run();
	}

	private static final class WorkerThread extends Thread
	{
		private final ThreadPoolImpl	threadPool;

		public WorkerThread(final ThreadPoolImpl threadPool,
				final String threadName)
		{
			super(threadName);

			this.threadPool = threadPool;
		}

		@Override
		public void run()
		{
			IJob job = null;

			while (true)
			{
				synchronized (this.threadPool)
				{
					job = this.threadPool.jobs.poll();
				}

				if (null != job)
				{
					try
					{
						job.run();
					}
					catch (final Throwable t)
					{
						job.onThrowable(t);
					}

					job = null;
				}
				else
				{
					synchronized (this.threadPool)
					{
						try
						{
							this.threadPool.wait();
						}
						catch (final InterruptedException exception)
						{
							Thread.currentThread().interrupt();
						}
					}
				}
			}
		}
	}

	private static final class ThreadPoolImpl implements IThreadPool
	{
		private final Queue<IJob>	jobs;

		public ThreadPoolImpl(final int poolSize)
		{
			this.jobs = new ArrayDeque<>();

			for (int index = 0; index < poolSize; index++)
			{
				final WorkerThread workerThread = new WorkerThread(this,
						"ThreadPool: Worker" + index);
				workerThread.start();
			}
		}

		@Override
		public final void submitJob(final IJob job)
		{
			if (null != job)
			{
				synchronized (this)
				{
					this.jobs.add(job);
					this.notifyAll();
				}
			}
		}
	}

	private static final int	THREAD_POOL_SIZE	= 5;

	private static IThreadPool	THREAD_POOL_IMPL;

	public static final IThreadPool getInstance()
	{
		if (null == ThreadPool.THREAD_POOL_IMPL)
		{
			THREAD_POOL_IMPL = new ThreadPoolImpl(THREAD_POOL_SIZE);
		}

		return THREAD_POOL_IMPL;
	}
}