private void waiting() {
		_pauseLock.lock();
		try {
			while (_paused) {
				try {
					_pauseCondition.await();
				} catch (InterruptedException e) {
					Thread.currentThread().interrupt();
				}
			}
		} finally {
			_pauseLock.unlock();
		}
	}
Starts the evolution worker with the given evolution result callback. The
callback may be null.

@param callback the {@code EvolutionResult} callback. The first parameter
       contains the current result and the second the best.
jenetics.example/src/main/java/io/jenetics/example/image/EvolvingImagesWorker.java