Wow, this has a really long post title.

Basically what I just figured out is how to delete the default domain that is created by the integrated Application Server (weblogic) by Jdeveloper.

Open Terminal.app

cd  ~/.jdeveloper/

Here you’ll find various folders, go into the one that resembles systemjdevversion for example

cd system12.1.2.0.40.66.68

then delete folder DefaultDomain

rm -Rf DefaultDomain

After this just restart jdeveloper and you can create a default domain again.