Will do my best to help.
First off, much as instructing newbies to use 'vi' is a great wheeze, I don't think you want to learn it just for this. You are better off using the graphical editor which come with your gnome/kde desktop. Just look in the menus - it should be obvious.
A good editor when you only have a terminal is 'pico', or the GPL clone 'nano'. One or the other should be on your distro. You would type:
pico -w ~/.bashrc
The -w option turns of line wrapping, which if left on may corrupt system files by splitting long lines.
The quickest way to achieve your stated goal of installing bluej is to leave the .bashrc alone and simply type the full command:
/usr/java/j2sdk1.4.2_04/bin/java -jar bluej135.jar
(Assuming that that path is indeed correct).
The best way to make this all work reliably is to symlink /usr/java/j2sdk1.4.2_04/ to /usr/local/java, and then link /usr/local/java/bin/java to /usr/bin/java - so the executable will be found in the standard path and if you upgrade the JRE you only need to re-point the symlink.
So your homework is to read up on symlinks, environment variables and the shell $PATH.