Eclipse stopped working after upgrade to Mountain Lion. My initial guess was that it could be due to Java not being available. I installed Oracle Java 7.
Even then, eclipse wasn’t starting up. I tried changing eclipse.ini to set the VM. No avail.
Finally, I realised it could be due to the new security settings in Mountain Lion. To resolve this, go to System Preferences > Security & Privacy > General, and choose the check-box for “Anywhere.” (You may need to unlock the settings before you can make this change)
Finally, Eclipse started working.
Other useful information I came across during my search:
[Thread from StackOverflow]
JDK 7 will be installed under /Library/Java/JavaVirtualMachines/1.7.0.jdk, JDK 6 under /System/Library/Java/JavaVirtualMachines.
To trick OS X to accept Java 7 instead of proposing to install Java 6 a simple symlink is enough:
sudo mkdir /System/Library/Java/JavaVirtualMachines
sudo ln -s /Library/Java/JavaVirtualMachines/1.7.0.jdk /System/Library/Java/JavaVirtualMachines/1.6.0.jdk
Most Java Programms will run with this little hack without the need to install Java 6.
[Edit eclipse.ini to specify a Java version]