Compiling and running java source code from the terminal??

Hi, I'm struggling to compiile my java source code and run it from the terminal.... (Yeah I'm new to OpenSUSE/linux in general)

I've made a simple program which I then try to compile using "javac Welcome.java" and I get...

green@linux-v85t:~> cd Desktop
green@linux-v85t:~/Desktop> cd Java
green@linux-v85t:~/Desktop/Java> ls
test.java Welcome.java
green@linux-v85t:~/Desktop/Java> javac Welcome.java
If 'javac' is not a typo you can use command-not-found to lookup the package that contains it, like this:
cnf javac
green@linux-v85t:~/Desktop/Java>


Now on Windows I remember I had to do something with the environment variables but I have no idea how to do that here.

java -version gives me...

java version "1.7.0_15"
OpenJDK Runtime Environment (IcedTea7 2.3.7) (suse-8.3.1-i386)
OpenJDK Server VM (build 23.7-b01, mixed mode)

Any help is much appreciated.

Thanks

Also, how would I go about updating my java version?