public HashSet<String> getSuccessfulNodes() {
        final HashSet<String> successfulNodes = new HashSet<>(matchedNodes);
        successfulNodes.removeAll(failedNodes.keySet());
        return successfulNodes;
    }
public HashSet < String > getSuccessfulNodes ( ) { final HashSet < String > successfulNodes = new HashSet < > ( matchedNodes ) ; successfulNodes . removeAll ( failedNodes . keySet ( ) ) ; return successfulNodes ; }
@return the matched nodes less the failed nodes.