Attaching some code to session start and end in Linux

I'm trying to execute some code (let's call it login.java) when I log in and out of my linux machine. Is there any way to do this? I'm looking for perhaps a way to trigger the code? I've thought of just putting it in my .bash_login but preferably the code would launch on normal login, not when I start my terminal.

Take a look @ this posts

http://synapse.wordpress.com/2007/03/24/run-a-script-on-startup-shutdown-in-linux/

http://www.linuxfromscratch.org/hints/downloads/files/execute-session-scripts-using-kdm.txt

If you are using bash shell it doable. check out the man bash. .bashrc and .bash_logout