question: public Point2D ( double x , double y ) { if ( Double . isInfinite ( x ) || Double . isInfinite ( y ) ) throw new IllegalArgumentException ( "Coordinates must be finite" ) ; if ( Double . isNaN ( x ) || Double . isNaN ( y ) ) throw new IllegalArgumentException ( "Coordinates cannot be NaN" ) ; if ( x == 0.0 ) this . x = 0.0 ; else this . x = x ; if ( y == 0.0 ) this . y = 0.0 ; else this . y = y ; }
target:  Initializes a new point (x, y).