I think that I've tracked down an NPE in the crosby_integration branch of the splitter. The SplitProcessor is using a BlockingQueue to queue up elements for writing. The poll() method can potentially return a null if the queue is empty. My question is, should the poll() method call be switched to a take() method call - the take() method will block if the queue is empty, or should I guard the usage of elements for null like in the patch below? Index: src/uk/me/parabola/splitter/SplitProcessor.java =================================================================== --- src/uk/me/parabola/splitter/SplitProcessor.java (revision 161) +++ src/uk/me/parabola/splitter/SplitProcessor.java (working copy) @@ -320,13 +320,14 @@ } else { synchronized (workPackage) { while (!workPackage.inputQueue.isEmpty()) { - ArrayList<Element> elements =null; + ArrayList<Element> elements = null; try { elements = workPackage.inputQueue.poll(); - for (Element element : elements ) { - processElement(element, workPackage.writer); + if (elements != null) { + for (Element element : elements ) { + processElement(element, workPackage.writer); + } } - } catch (IOException e) { throw new RuntimeException("Thread " + Thread.currentThread().getName() + " failed to write element ", e); } -- Jeff Ollie