Using the available classes from the 2D Graphics API.

Rectangle r1 = new Rectangle(100, 100, 100, 100); Line2D l1 = new
Line2D.Float(0, 200, 200, 0); 
System.out.println("l1.intsects(r1) = " + l1.intersects(r1));

传送门:
1. How to check intersection between a line and a rectangle?
2. How do you detect where two line segments intersect?