@Override
            public boolean hasNext() {
                if (null != this.nextResult) {
                    return true;
                } else {
                    advance();
                    return null != this.nextResult;
                }
            }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/util/iterator/IteratorUtils.java