Java Program - Track Position Of Imaginary Ball As It Bounces Around Imaginary Box

I am working on a program that asks me to track the position of an imaginary ball as it bounces around an imaginary box. The user gives me input for the starting position of the ball (x,y), the bottom-left boundaries of the box (xl, yl), the top right boundaries (xr, yr) and the angle. The program then needs to find where the ball will hit the box, and then print that location and find the new angle for the next point. My program currently works in most cases if the angle is less than pi.

Here is my code

public class BouncyBall {
public static void main(String args[]){
if (args.length != 8) {
System.out.println("Error: usage is X, Y, Angle, Xl, Yl, Xr, Yr,N");
System.exit(1);
}
double x,y,xl,yl,xr,yr,angle;
int n;
x=Double.parseDouble(args[0]);
y=Double.parseDouble(args[1]);

[Code] .....