Ball class JAVA

            public class Ball{
                public Random random = new Random();
                public double ang,x,y,incX,incY,vel;
                public Bitmap img = BitmapFactory.decodeResource(getResources(), R.drawable.ball);
                public double w = img.getWidth();
                public double h = img.getHeight();
                public double inc = 0.01;
                public void setRandomAngle(){
                    this.ang = this.random.nextDouble()*Math.PI*2;
                }
                public void calcIncVars(){
                    this.incX = Math.cos(this.ang);
                    this.incY = Math.sin(this.ang);
                }
                public void serve(){
                    this.x = 240-this.img.getWidth();
                    this.y = 854/2-this.img.getHeight();
                    this.setRandomAngle();
                    this.calcIncVars();
                }
                public void move(){
                    this.vel = this.vel + this.inc;
                    this.x = this.x +this.incX*this.vel;
                    this.y = this.y +this.incY*this.vel;
                    checkScreenCollisions();
                }
                public void checkScreenCollisions(){
                    if ( this.x + this.w >= 480 || this.x <=0){
                        this.incX = -this.incX;
                    }
                    if ( this.y + this.h >= 854 || this.y <=0){
                        this.incY = -this.incY;
                    }
                }
                public void blit(Canvas canvas,Paint mPaint){
                    canvas.drawBitmap(this.img, (float) this.x,(float) this.y,mPaint);
                }
            }