java.util.* can't be resolved?

Hi

I got this error in my project, after a long time haven't opened the workspace.

I searched the internet, most of people is due to the unbound thing mentioned here, but I don't see anything wrong.

http://www.eclipse.org/forums/index.php/m/252831/

But in the list of library, I don't see java.util.jar and many other jars, in the attached image. I've tried remove and add the JRE lib, still the same. How can I fix this?

https://lh6.googleusercontent.com/-BofoboUOjTM/TgnxoXs7A0I/AAAAAAAAEhI/1s0ZwWWn0i0/java.util.png

Thanks
Jirong