Mac de Jdeveloper kurmadan once:

Source: http://www.oracle.com/technology/products/jdev/htdocs/11/knownissues.html#install4

Installing JDeveloper on Mac OS

Some additional steps are required to install JDeveloper on Mac OS beyond what is documented in the installation guide. Please refer to the installation guide for additional details on installing JDeveloper for Mac OS X.

1. Make Java 6 the default VM.

• Run Java Preferences (in /Applications/Utilities/Java)
• Move the Java SE 6 (64 Bit) to the top of the Java application versions list (General tab)

2. Create a symbolic link for classes.jar

• Enable root user:
  • Open the Directory Utility app from Applications - Utility
  • Ensure the settings are unlocked (click the lock if necessary)
  • Choose Edit > Enable Root User and provide the root user password.
  • Note, you can return to this same screen to disable root user after creating the symbolic link
• Create the symbolic link:

  cd /SystemLibrary/Frameworks/JavaVM.framework/Versions/1.6.0/Home/
  su root
  mkdir jre
  cd jre
  mkdir lib
  cd lib
  ln -s ../../../Classes/classes.jar rt.jar