Geotools always return Multipolygon type for shapefile

Question

I want to know the true type of Geometry using GeoTools (point, polygon, multipolygon). GeoTools always returns me as a MultiPolygon, and my object has this format for example:

"geometry": {"type": "polygon", "coordinates": [-86.577085000372449, 34.793410999917739], [-86.57692100000412, 34.793837999823893], [-86.576509999936491, 34.794884000396337]

Currently I have the following code:

Map <String, Object> map = new HashMap <> ();
        map.put ("url", file.toURI (). toURL ());

        DataStore dataStore = DataStoreFinder.getDataStore (map);
        String typeName = dataStore.getTypeNames () [0];

        FeatureSource <SimpleFeatureType, SimpleFeature> source = dataStore
                .getFeatureSource (typeName);

        FeatureCollection <SimpleFeatureType, SimpleFeature> collection = source.getFeatures ();
        try (FeatureIterator <SimpleFeature> features = collection.features ()) {
            while (features.hasNext ()) {
                SimpleFeature feature = features.next ();
              
               feature.getAttribute ("the_geom"). toString ();
}

Answer 1

Because Shapefiles can only handle one type of geometry if any of your features contains a multipolygon the geometry column needs to be of type multipolygon.

You can check if a multipolygon is really a simple polygon by using the getNumGeometries method.

try (FeatureIterator<SimpleFeature> features = collection.features()) {
  while (features.hasNext()) {
    SimpleFeature feature = features.next();
    MultiPolygon geom = (MultiPolygon) feature.getDefaultGeometry();
    String type = "Polygon";
    if(geom.getNumGeometries()>1) {
      type = "MultiPolygon";
    }
    System.out.println(feature.getAttribute("STATE_NAME")+" "+type);
  }
}

As a stylistic note you should use the URLs utility class to convert your file to a URL otherwise you run the risk of failures in windows environments.

File file = new File("/home/ian/Data/states/states.shp");
map.put("url", URLs.fileToUrl(file));