Can't save project preferences in Eclipse

Question

All I am trying to do is to set the Java compiler for my project as 5.0. It is 1.4 by default. When I try to save by pressing OK button I get the following error.

Pr

Answer 1

Check the project's Properties -> Java Compiler, and make sure the 'Compiler compliance level' is 1.8 or 1.7 instead of 1.4.

If this still fails to remove the error, deleting the .settings folder certainly works.