JDeveloper and Upgrading Your JDK on Ubuntu
By Duncan Mills-Oracle on May 19, 2010
Assuming that you've installed from the jar version of the JDeveloper installer, then the JDK that you specified at install time will be recorded in the .jdev_jdk file in your home directory.
However, be aware that this is not the only reference to the absolute path of the JDK. When you run the embedded WebLogic for the first time then the
script will be created, and associated with that, the setDomainEnv.sh script in the same directory.
So, if you do want to change the JDK location be sure to change this file as well.
Finally, if you blow the default domain away then you need to make sure that the wlst scripts that re-create it will correctly pick up the new JDK location.
(or of course do everything with symbolic links)