question: public static int intersectLineLine ( Line2D a , Line2D b , Point2D intersect ) { double a1x = a . getX1 ( ) , a1y = a . getY1 ( ) ; double a2x = a . getX2 ( ) , a2y = a . getY2 ( ) ; double b1x = b . getX1 ( ) , b1y = b . getY1 ( ) ; double b2x = b . getX2 ( ) , b2y = b . getY2 ( ) ; return intersectLineLine ( a1x , a1y , a2x , a2y , b1x , b1y , b2x , b2y , intersect ) ; }
target:  Compute the intersection of two line segments.