add method
Implementation
void add(Geometry g) {
if (g.isEmpty()) return;
if (g is Polygon)
addPolygon(g);
// LineString also handles LinearRings
else if (g is LineString)
addLineString(g);
else if (g is Point)
addPoint(g);
else if (g is MultiPoint)
addCollection(g);
else if (g is MultiLineString)
addCollection(g);
else if (g is MultiPolygon)
addCollection(g);
else if (g is GeometryCollection)
addCollection(g);
else
throw new UnsupportedError(g.runtimeType.toString());
}