1. Transfer the .jad and .jar files to the phones memory to the 'Other Files' folder.
You can transfer the files from Samsung PC Studio's 'Phone Explorer', or just transfer it straight to the memory card and move it to 'Other Files' from the phone's menu.
If you don't have a .jad file, you can download 'Jad Maker' (Google) and make a new one.
Download from this site as they also provide .jad files [Only registered and activated users can see links. ]
The screen size is 240x320.
2. Exit all menus and type in this code: *#9998*4678255#.
You should now get an 'Activated' message. Java install is enabled.
3. Go to the 'Other Files' folder and select the .jad file (should be 1kb).
Press 'Options' (left touch key) and you should get a 'Do you want to install' question.
Press 'Yes' to install.
4. To deactivate Java install, simply type the same code again.
You should now get a 'Deactivated' message.