JDeveloper11g Startup error

I installed JDeveloper11g Studio Edition with no JDK bundle but when i tried to start JDeveloper, it gave me error

Unable to start Java Virtual Machine located at ....

In order to fix this type of error, go to installation_directoy\Middleware\JDeveloper\jdev\bin folder
and edit file jdev.conf.
Locate line "AddVMOption -XX:MaxPermSize=256M".
Now add another line just below this line:

AddVMOption -Xmx256M