code: private Area getArea(double simplifyTolerance, BoundingBox boundingBox,
  			ProjectionTransform transform, Polygon polygon) {
  
  		Area area = null;
  
  		for (LineString ring : polygon.getRings()) {
  
  			Path2D path = getPath(simplifyTolerance, boundingBox, transform,
  					ring);
  			Area ringArea = new Area(path);
  
  			if (area == null) {
  				area = ringArea;
  			} else {
  				area.subtract(ringArea);
  			}
  
  		}
  
  		return area;
  	}
docs: Get the area of the polygon
  
  @param simplifyTolerance
  simplify tolerance in meters
  @param boundingBox
  @param transform
  @param lineString