• public void setColor(Color color) {this.color=color;}
• public void checkBoundry(Rectangle rect) { /* check if object crosses boundary */
• int nx = x+dx; /* caculate new location */
• int ny = y+dy;
• if ( (nx < rect.x) || (nx >= rect.x+rect.width) ) dx = -dx;
• if ( (ny < rect.y) || (ny >= rect.y+rect.height) ) dy = -dy;
• }
• public void move(Graphics g) { /* move object */
• x += dx; /* update location */
• y += dy;
• paint(g);
• }
• public void paint(Graphics g) /* actually draw point */
• { g.setColor(color);
• g.drawOval(x,y,1,1);}

}