code: @Pure
  	@Override
  	public int distance(Point3D p1) {
  	      double  dx, dy, dz;
  	      dx = this.x-p1.getX();  
  	      dy = this.y-p1.getY();
  	      dz = this.z-p1.getZ();
  	      return (int)Math.sqrt(dx*dx+dy*dy+dz*dz);
  	}
docs: {@inheritDoc}