Eclipse IDE started and broken - cannot find any Java classes

Question

I haven't started my Eclipse Java EE Kepler in a while, and now it ended up with the following error on every project in my workspace:

http://i62.tinypic.com/30rsfgm.png

I'm not sure what happened here.

Answer 1

Due to a recent Java update, the JRE settings for the projects in Eclipse got unbound.

To fix this, one must set the current JRE on their computer as the JRE for the project library on the build path (This can also be found by going to the Problems tab, right clicking the error "unbound classpath container", then press Quick Fix):

http://i62.tinypic.com/5a438i.png

Then click on the JRE System Library, edit, and set it as an Installed JRE:

http://i58.tinypic.com/14vntqp.png