I have a few original MultiPolygons that contain holes...I would like to extract the Polygons and recreate them WOTHOUT the holes. how is this done?

Original MultiPolygon. https://gist.github.com/boundaries-io/978eaa4a10df9467638a5eb9259c84e6 enter image description here

when breaking up the Multipolygon

   org.geojson.MultiPolygon reCreateMultiPolygon = new org.geojson.MultiPolygon();
             for (List<List<LngLatAlt>> polygonPoints : multiPolygon.getCoordinates()) {
                for (List<LngLatAlt> point : polygonPoints) {
                    Polygon p = new Polygon(point);
             String fileName2 =   saveToFileSystem(reCreateMultiPolygon);

The this is treating each polygon as its own polygon...I am unclear how to recreate this with the holes intact...not treat them as normal polygons. results:/ Incorrect recreated MultiPolygon https://gist.github.com/boundaries-io/89e51458e9f5509b5457f9033474bc2d enter image description here

my end goal is to create a convert that does a org.geojson.MultiPolygon to rg.springframework.data.mongodb.core.geo.GeoJsonMultiPolygon to save in Mongodb via spring data mongodb. if this can be done via JTS,geotools,etc. thats fine...

1 Answer 1


If you just want the individual polygons (including the holes) then something like:

  MultiPolygon mp = (MultiPolygon) g;
  List<Polygon> polys = new ArrayList<>();
  for (int i = 0; i < mp.getNumGeometries(); i++) {
    Polygon poly = (Polygon) mp.getGeometryN(i);

Will give you a List of Polygons. Note, these are JTS geometries not geojson ones.


For just the holes you need to do something like:

private List<Polygon> getHoles(Geometry mp) {
    GeometryFactory gf = new GeometryFactory();
    List<Polygon> holes = new ArrayList<>();
    if (mp instanceof MultiPolygon || mp instanceof Polygon) {
      for (int i = 0; i < mp.getNumGeometries(); i++) {
        Polygon poly = (Polygon) mp.getGeometryN(i);
        for (int h = 0; h < poly.getNumInteriorRing(); h++) {
          LinearRing hole = poly.getInteriorRingN(h);
    return holes;
  • i want to re-create the MultiPolygon object so when saving it will contain holes.... using what you have will recreate the MultiPolygon treating holes as normal polygons. basically how do i create a multiPolygon that will describe the 'holes'
    – Jeryl Cook
    Sep 3, 2020 at 14:30
  • updated question..with my end goal.
    – Jeryl Cook
    Sep 3, 2020 at 15:21
  • now that i can get the holes....how do i use them to make the original MultiPolygon(that contain the holes?
    – Jeryl Cook
    Sep 3, 2020 at 15:44
  • 1
    What do you mean? if you want the holes in the original filled - see gis.stackexchange.com/questions/364571/…
    – Ian Turton
    Sep 3, 2020 at 15:49
  • Ahh my mistake I meant recreate without holes...like the original.
    – Jeryl Cook
    Sep 3, 2020 at 16:34

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