public class InclineSegmentSimulator {

    // Separate acceleration, velocity and distance for x and y shadows.
    double ax = 0, ay = 0;
    double vx = 0, vy = 0;
    double x = 0, y = 0;

    // Time and time-step.
    double t = 0;
    double delT = 0.001; 

    // Vertical acceleration.
    double g = 9.8;
    

    public double run (double x1, double y1, double x2, double y2, double initvx, double initvy)
    {
        // Acceleration along incline: g*sin(alpha).
        double hyp = distance (x1,y1, x2,y2);
        double xDiff = Math.abs (x1-x2);
        double yDiff = Math.abs (y1-y2);
        double sineOfAngle = yDiff / hyp;
        double cosineOfAngle = xDiff / hyp;

        // Acceleration along incline.
        double a = g * sineOfAngle;

        // Acceleration along x and y.
        ax = a * cosineOfAngle;
        ay = a * sineOfAngle;

	// Initialize velocity components.
        vx = initvx;  vy = initvy;

        // Distance components.
        x = x1;  y = y1;

        t = 0;

	while (true) {
	    // Update time.
	    t += delT;

            // Increase velocity according to appropriate acceleration.
            vx = vx + delT * ax;
            vy = vy - delT * ay;

            // Increase distance in each direction according to appropriate velocity.
            x = x + delT * vx;
            y = y + delT * vy;

	    if ((x > x2) && (y < y2)) {
                // NOTE: this assumes that (x2,y2) is to the right and below.
                break;
	    }
	}

        return t;
    }


    double distance (double x1, double y1, double x2, double y2)
    {
	return Math.sqrt ((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
    }


    public double getVx ()
    {
        return vx;
    }
    

    public double getVy ()
    {
        return vy;
    }
    
}