DefensiveThreadPoolExecutor

gistfile1.java

private class DefensiveThreadPoolExecutor extends ThreadPoolExecutor {

	public DefensiveThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit,
			LinkedBlockingQueue<Runnable> workQueue, ThreadFactory factory, RejectedExecutionHandler handler) {
		super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, factory, handler);
	}

	/**
	 * "Last" task issues a signal that queue is empty after task processing was completed.
	 */
	@Override
	protected void afterExecute(Runnable r, Throwable t) {
		if (state == PREPARE) {
			closeLock.lock(); // only one thread will pass when closer thread is awaiting signal
			try {
				if (getQueue().isEmpty() && state < SHUTDOWN) {
					System.out.println("Issueing signal that queue is empty ...");
					isEmpty.signal();
					state = SHUTDOWN; // -> no other thread can issue empty-signal
				}
			} finally {
				closeLock.unlock();
			}
		}
		super.afterExecute(r, t);
	}
}