ok, let's try to explain it better
So, you want to install j2sdk-1_4_1_02-fcs-linux-i586.rpm package.
I guess you have already downloaded it.
1. install it as superuser.
rpm -i j2sdk-1_4_1_02-fcs-linux-i586.rpm
2. look for it:
it should be in /usr/java/jdkSomething
or try to locate it typing
locate jdk1.4. remember the path to it, something like
try doing cd /usr/java/jdk --and press tab key to see what is in there
3. add it to the PATH
In your home directory /home/yourUserName look for .bashrc file or create it.
add a line like this:
PATH=/usr/java/jdk1.3.1_02/bin/:$PATH but instead /usr/java/jdk1.3.1_02 put the path where the java binary is: it should be /usr/java/jdk1.4.1_02/bin/
4.open a new terminal
now it should work if you type java.