code: private static void getLinealGeometry(ArrayList<LineString> lines, Geometry geometry) {
           for (int i = 0; i < geometry.getNumGeometries(); i++) {
              Geometry subGeom = geometry.getGeometryN(i);
              if(subGeom instanceof LineString){
                  lines.add((LineString) subGeom);
              }
              else if (subGeom instanceof GeometryCollection){
                  getLinealGeometry(lines, subGeom);
              }
          }
      }
docs: Filter line from a geometry
  @param lines
  @param geometry