question: public static double distance ( VisualItem vi1 , VisualItem vi2 ) { double dx = vi1 . getX ( ) - vi2 . getX ( ) ; double dy = vi1 . getY ( ) - vi2 . getY ( ) ; return Math . sqrt ( dx * dx + dy * dy ) ; }
target:  Get the distance between the x,y points of two VisualItems.