question: public void zoom ( double x , double y , double factor ) { double rangeX = Math . abs ( currentExtent . getMaxX ( ) - currentExtent . getMinX ( ) ) ; double rangeY = Math . abs ( currentExtent . getMaxY ( ) - currentExtent . getMinY ( ) ) ; currentExtent . setMinX ( x - ( rangeX * factor ) / 2.0 ) ; currentExtent . setMinY ( y - ( rangeY * factor ) / 2.0 ) ; currentExtent . setMaxX ( x + ( rangeX * factor ) / 2.0 ) ; currentExtent . setMaxY ( y + ( rangeY * factor ) / 2.0 ) ; addToExtentHistory ( currentExtent ) ; }
target:  Performs a zoom and center operation