code: private static boolean polylineDisjointPolyline_(Polyline polyline_a,
  			Polyline polyline_b, double tolerance,
  			ProgressTracker progress_tracker) {
  		// Quick rasterize test to see whether the the geometries are disjoint.
  		if (tryRasterizedContainsOrDisjoint_(polyline_a, polyline_b, tolerance,
  				false) == Relation.disjoint)
  			return true;
  
          MultiPathImpl multi_path_impl_a = (MultiPathImpl)polyline_a._getImpl();
          MultiPathImpl multi_path_impl_b = (MultiPathImpl)polyline_b._getImpl();
  
          PairwiseIntersectorImpl intersector_paths = new PairwiseIntersectorImpl(multi_path_impl_a, multi_path_impl_b, tolerance, true);
  
          if (!intersector_paths.next())
              return false;
  
  		return !linearPathIntersectsLinearPath_(polyline_a, polyline_b,
  				tolerance);
  	}
docs: Returns true if polyline_a is disjoint from polyline_b.