Polygon originalArea = (Polygon)mapArea;
// NB: the buffer method always returns a polygonal result.
Polygon expandedArea = (Polygon)mapArea.buffer( getOffTheMapDistance(), DEFAULT_CAP_EDGES, DEFAULT_BUFFER_CAP_TYPE );
GeometryFactory geometryFactory = mapArea.getFactory();
LinearRing expandedAreaBoundary = geometryFactory.createLinearRing( expandedArea.getExteriorRing().getCoordinates() );
LinearRing originalAreaBoundary = geometryFactory.createLinearRing( originalArea.getExteriorRing().getCoordinates() );
this.justOffTheMapArea = geometryFactory.createPolygon( expandedAreaBoundary, new LinearRing[]{ originalAreaBoundary } );
}
else if (mapArea instanceof MultiPolygon)