Can not compile enums in Eclipse

Question

While trying to introduce enums in my Android project in Eclipse, I encountered with the following problem: Compiler says:

1. The type java.lang.Enum cannot be re

Answer 1

Close project the project with the error.

Open a different project and launch in emulator. Close the alternative project.

Open the original project with the error which should no longer be evidenced.

Don't know why it works or if actually launching the app is necessary but it clears the error .