I upgraded to Ubuntu 12.04 this morning. After the upgrade I fired up Eclipse and noticed that it was lacking Java integration: Java Perspectives were gone, the option to create a new Java project was missing, the menu item to build existing Java projects was grayed out, etc. Everything was working fine before upgrading.
:~$ echo $JAVA_HOME /usr/lib/jvm/default-java :~$ which java /usr/bin/java
If I can provide any additional helpful info, please let me know. I'm still relatively new to the Linux/Java world, so thanks in advance for the help.