Thread: Java Program Help

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. Any help is apreciated! Here is my code

//2014-09-16
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]);
		angle=Double.parseDouble(args[2]);
		xl=Double.parseDouble(args[3]);
		yl=Double.parseDouble(args[4]);
		xr=Double.parseDouble(args[5]);
		yr=Double.parseDouble(args[6]);
		n=Integer.parseInt(args[7]);
		if ((x>xr || x<xl)||(y>yr || y<yl)) {
			System.out.println("Error: Initial point is not within the box");
			System.exit(1);
		}
		System.out.printf("%f, %f\n",x,y);
		System.out.printf("Starting angle is %f Pi.\n", angle/Math.PI);
		double startX, startY, endX, endY;
		startX=x;
		startY=y;
		if (angle==0) {
			System.out.printf("Ball bounces back and forth between (%.2f, %.2f) and (%.2f, %.2f).\n", xr,y,xl,y);
		}else if (angle==Math.PI) {
				System.out.printf("Ball bounces back and forth between (%.2f, %.2f) and (%.2f, %.2f).\n", xl,y,xr,y);
		}else if (angle==(Math.PI/2)) {
					System.out.printf("Ball bounces up and down between (%.2f, %.2f) and (%.2f,%.2f). \n", x, yr,x, yl);
		}else if (angle == (3*Math.PI/2)) {
			System.out.printf("Ball bounces up and down between (%.2f, %.2f) and (%.2f,%.2f). \n", x, yl,x, yr);
		}else {
		for (int i=0;i<n;i++) {
			//declare local variables
			while (angle>(2*Math.PI)) {
			angle=angle-(2*Math.PI);
		}while (angle<0) {
			angle=angle+(2*Math.PI);
		}
			double distance;
 
				if(angle>=0 && angle<(Math.PI/2)) {
				//Quadrant 1	
				//
				endX=getX(yr,startY, startX, angle);
				endY=getY(xr, startY, startX, angle);
					//Use the distance formula to find which one is closer
				distance=getDistance(endX, endY, startX, startY, xr, yr);
				//get new x, y and angle variables
				if(distance==1) {
					startX=endX;
					startY=yr;
					}else if (distance==2) {
					startX=xr;
					startY=endY;
					}else if (distance==3){
					startX=xr;
					startY=yr;
					}
				angle=getNewAngle(distance, angle);		
				}else if (angle>(Math.PI/2) && angle<(Math.PI)) {
					//Quadrant 2	
					//
					endX=getX(yr,startY, startX, angle);
					endY=getY(xl, startY, startX, angle);
						//Use the distance formula to find which one is closer
					distance=getDistance(endX, endY, startX, startY, xl, yr);
					//get new x, y and angle variables
					if(distance==1) {
						startX=endX;
						startY=yr;
						}else if (distance==2) {
						startX=xl;
						startY=endY;
						}else if (distance==3){
						startX=xl;
						startY=yr;
						}
					angle=getNewAngle(distance, angle);
				}else if (angle>(Math.PI) && angle<((3*Math.PI)/2)) {
					//Quadrant 3	
					//
					endX=getX(yl,startY, startX, angle);
					endY=getY(xl, startY, startX, angle);
						//Use the distance formula to find which one is closer
					distance=getDistance(endX, endY, startX, startY, xl, yl);
					//get new x, y and angle variables
					if(distance==1) {
						startX=endX;
						startY=yl;
						}else if (distance==2) {
						startX=xl;
						startY=endY;
						}else if (distance==3){
						startX=xl;
						startY=yl;
						}
					angle=getNewAngle(distance, angle);
				}else if (angle>((3*Math.PI)/2) && angle<(2*Math.PI)) {
					//Quadrant 4	
					//
					endX=getX(yr,startY, startX, angle);
					endY=getY(xl, startY, startX, angle);
						//Use the distance formula to find which one is closer
					distance=getDistance(endX, endY, startX, startY, xr, yl);
					//get new x, y and angle variables
					if(distance==1) {
						startX=endX;
						startY=yl;
						}else if (distance==2) {
						startX=xr;
						startY=endY;
						}else if (distance==3){
						startX=xr;
						startY=yl;
						}
					angle=getNewAngle(distance, angle);
				}
 
 
			System.out.printf("%2f, %2f\n", startX, startY);
			System.out.printf("New angle is %f Pi\n", angle/Math.PI);
		}
		}
	}
 
public static double getY(double xMax, double startY, double startX, double angle) {
	double endY=(Math.tan(angle)*(xMax-startX))+startY;
	return endY;
};
public static double getX(double yMax, double startY, double startX,double angle){
	double endX=((yMax-startY)/Math.tan(angle))+startX;
	return endX;
	};
public static double getDistance(double endX, double endY, double startX, double startY, double xMax, double yMax){
	double distance1=Math.sqrt(((endX-startX)*(endX-startX))+((yMax-startY)*(yMax-startY)));
	double distance2=Math.sqrt(((xMax-startX)*(xMax-startX))+((endY-startY)*(endY-startY)));
	if (distance1< distance2) {
		return 1.0;
		//hits top/bottom
	}else if (Math.abs(distance1)>Math.abs(distance2)) {
		return 2.0;
		//hits left/right side
	}
	else {
		return 3.0;
		//hits corner
	}
 
};
public static double getNewAngle(double distance, double angle){
	double newAngle=0;
	double anglePlus;
	if (angle> 0 && angle<(Math.PI/2)){
		//Quadrant 1
		anglePlus=angle;
		if(distance==1) {
		newAngle=(2*Math.PI)-anglePlus;
		}else if (distance==2) {
		newAngle=(Math.PI)-angle;
		}else if (distance == 3) {
		newAngle=anglePlus+Math.PI;	
		}
	}else if (angle> (Math.PI/2) && angle<(Math.PI)){
		//Quadrant 2
		anglePlus=(angle-(Math.PI/2));
		if(distance==1) {
		newAngle=(3*Math.PI/2)-anglePlus;
		}else if (distance==2) {
		newAngle=(Math.PI/2)-anglePlus;
		}else if (distance == 3) {
		newAngle=angle+Math.PI;	
		}
	}if (angle> Math.PI && angle<((3*Math.PI)/2)){
		//Quadrant 3
		anglePlus=angle-Math.PI;
		if(distance==1) {
		newAngle=(Math.PI)-anglePlus;
		}else if (distance==2) {
		newAngle=(2*Math.PI)-anglePlus;
		}else if (distance == 3) {
		newAngle=angle+Math.PI;	
		}
	}if (angle> ((3*Math.PI)/2) && angle<(2*Math.PI)){
		//Quadrant 4
		anglePlus=angle-((3*Math.PI)/2);
		if(distance==1) {
		newAngle=(Math.PI/2)-anglePlus;
		}else if (distance==2) {
		newAngle=(3*Math.PI/2)-anglePlus;
		}else if (distance == 3) {
		newAngle=angle+Math.PI;	
		}
	}

THANKS!!!

This sounds more like a math problem than a java programming problem.
Is there a specific math expression or equation that you are having problems coding in java?
Post it and show what you have coded to solve it.