I encountered this error when deploying a Google AppEgine app:

Java 6 applications cannot be deployed to Google App Engine from any version of the SDK… you can request that your application be whitelisted for Java 6 deployment from http://goo.gl/ycffXq.

And so I have to add Java 7 SDK to Eclipse.

This is what you have to do:

1. Download & install Java 7 JDK

2. In Eclipse, go to Preferences > Java > Installed JREs > Add, then select the directory, which should be

   /Library/Java/JavaVirtualMachines/jdk1.7.0_51.jdk/Contents/Home

3. Tick the checkbox to make Java SE 7 the default

4. Go to Preferences > Java > Compiler > Compliance Level > Select 1.7

Test, and deploy!

There should not be any problem with migrating to Java 7.