code: public Point add(double x, double y, double z)
  	{
  		this.x += x;
  		this.y += y;
  		this.z += z;
  		return this;
  	}
docs: Adds the x, y and z coordinates to this {@link Point}.
  
  @param x the x
  @param y the y
  @param z the z
  @return the point