I recently installed Eclipse and all of a sudden my Java applications failed to build with the error:
Syntax error, parameterized types are only available if source level is 1.5
After a bit of Googling I figured out that Eclipse installed a different JVM and set it as the default one. On Ubuntu (at least) the way to change the default JVM is by typing this into the console:
sudo update-alternatives --config java
It will show you which JVM is currently selected and allow you to choose a different one as default.