code: public Coordinate[] getSiblingVertices(Geometry geometry, GeometryIndex index)
  			throws GeometryIndexNotFoundException {
  		if (index.hasChild() && geometry.getGeometries() != null && 
  				geometry.getGeometries().length > index.getValue()) {
  			return getSiblingVertices(geometry.getGeometries()[index.getValue()], index.getChild());
  		}
  		switch (index.getType()) {
  			case TYPE_VERTEX:
  			case TYPE_EDGE:
  				return geometry.getCoordinates();
  			case TYPE_GEOMETRY:
  			default:
  				throw new GeometryIndexNotFoundException("Given index is of wrong type. Can't find sibling vertices "
  						+ "for a geometry type of index.");
  		}
  	}
docs: Get the full list of sibling vertices in the form of a coordinate array.
  
  @param geometry
  The geometry wherein to search for a certain coordinate array.
  @param index
  An index pointing to a vertex or edge within the geometry. This index will then naturally be a part of
  a coordinate array. It is this array we're looking for.
  @return Returns the array of coordinate from within the geometry where the given index is a part of.
  @throws GeometryIndexNotFoundException
  geometry index not found