Line2D.Double telling me lines are intersecting when they don't

Question

In making a project for class, we are defining shapes (triangle, quadrilateral, pentagon) without the help of the Shape class obviously.

In my checks to make sure the shape is valid, I use Line2D.Double linesIntersect() to determine if the connections between two sets of points (p1-p4 x p2-p3). When I have my input to linesIntersect(double,double,double,double,etc) set to:

p1(-1,-1)
p2(-1,-11)
p3(5,0)
p4(5,5)

It tells me that the line from p1 to p4 crosses the line from p2 to p3. When in fact they should be two diagonal parallel lines.

Any help?

Answer 1

Sorry, but based on what you typed, p1, p4 is not parallel to p2, p3.

p1(-1,-1)
p4(5,5)

p2(-1,-11)
p3(5,0)

p1, p4 has a slope of 1.

p2, p3 has a slope of 11/6 or 1.83

If you want the lines to be parallel, then you need to change p3.

p3(5,-5)