This is the easy part. apt-get install mozilla-firefox

Download Java as per instructions already outlined here: Sun_jdk

Test to see if java works (or exists) - type: java -version

If you simply downloaded the tarball of the jdk1.5 - test with: /home/user/jdk1.5/bin/java -version

To link the java binary so it can be accessed anywhere: ln -s /home/user/jdk1.5/bin/java /usr/bin/

To link the Java Plugin for Firefox: ln -s /home/user/jdk1.5/jre/plugin/i386/ns7/libjavaplugin_oji.so ~/.mozilla/plugins/ //the above mozilla settings is on a per user basis, hence linking the file to ~/

I hope it works for you!

More info at:

http://stepien.com.pl/2006/11/26/java-on-debian-including-firefox-plugin/