Java & Linux : Fishing in the Desert: Ubuntu kdm gdm lxdm

I have installed Kubuntu-desktop and Lubuntu-desktop on top of Ubuntu
If I want to switch from gdm to kdm or lxdm :
In a terminal window one of the following commands can be used :

sudo dpkg-reconfigure gdm
sudo dpkg-reconfigure kdm
sudo dpkg-reconfigure lxdm