# Java Line/Line Intersections #

I've been working on a project for which I need to do some graphics-y things in Java, using the AWT portions of the Java libraries. Although Sun has been nice enough to include an `intersectsLine`

method in the `Line2D`

class, it simply does a boolean test, and doesn't actually return the intersection point. As a result, I've had to write up the following:

static boolean getLineLineIntersection(Line2D.Double l1, Line2D.Double l2, Point2D.Double intersection) { if (!l1.intersectsLine(l2)) return false; double x1 = l1.getX1(), y1 = l1.getY1(), x2 = l1.getX2(), y2 = l1.getY2(), x3 = l2.getX1(), y3 = l2.getY1(), x4 = l2.getX2(), y4 = l2.getY2(); intersection.x = det(det(x1, y1, x2, y2), x1 - x2, det(x3, y3, x4, y4), x3 - x4)/ det(x1 - x2, y1 - y2, x3 - x4, y3 - y4); intersection.y = det(det(x1, y1, x2, y2), y1 - y2, det(x3, y3, x4, y4), y3 - y4)/ det(x1 - x2, y1 - y2, x3 - x4, y3 - y4); return true; } static double det(double a, double b, double c, double d) { return a * d - b * c; }

The line intersection method is from MathWorld.

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