Update /etc/apt/sources.list with an woody or sarge entry. Select the ftp.easynet.be server. Then execute as root: apt-get update, then apt-get install j2re1.4.
Assuming you already have the correct sources added to your /etc/apt/sources.list file you should be able to simply run
sudo apt-get update
and then
sudo apt-get install j2re1.4