Java- Intersection point of a Polygon and Line

Question

Is there any function that will give me the intersection point of a Polygon and Line2D ?

I have a Polygon and a line segment that I know

Answer 1

If you are not restricted to use the Polygon and Line2D Objects I would recommend to use JTS.

• Create LinearRing geometry (your polygon).
• Create LineString geometry.
• Create intersection Point(s) using the intersection method.

Simple code example:

// create ring: P1(0,0) - P2(0,10) - P3(10,10) - P4(0,10)
LinearRing lr = new GeometryFactory().createLinearRing(new Coordinate[]{new Coordinate(0,0), new Coordinate(0,10), new Coordinate(10,10), new Coordinate(10,0), new Coordinate(0,0)});
// create line: P5(5, -1) - P6(5, 11) -> crossing the ring vertically in the middle
LineString ls = new GeometryFactory().createLineString(new Coordinate[]{new Coordinate(5,-1), new Coordinate(5,11)});
// calculate intersection points
Geometry intersectionPoints = lr.intersection(ls);
// simple output of points
for(Coordinate c : intersectionPoints.getCoordinates()){
    System.out.println(c.toString());
}

Result is:

(5.0, 0.0, NaN)
(5.0, 10.0, NaN)