Of course you can do it yourself and JDeveloper can teach you how to
do it!

Write whatever you want using JDeveloper and its wizards. Now look at
the code that JDeveloper has generated. That is the code you should
have written if you wanted to do it yourself and you can try a
variation of your task to see how you go.

I suspect that, after looking at the generated code, you will realize
that Java is a low-level language and will be duly grateful to
JDeveloper for saving you the effort of writing it.