question: public void filter ( Geometry g ) { if ( g instanceof Polygon ) { Polygon poly = ( Polygon ) g ; linework . add ( poly . getExteriorRing ( ) ) ; for ( int i = 0 ; i < poly . getNumInteriorRing ( ) ; i ++ ) { linework . add ( poly . getInteriorRingN ( i ) ) ; } } }
target:  Filters out all linework for polygonal elements