Another annoying eclipse error is the error below while trying to build a project:
After lot of waste of time (checking that project Y do exists etc), the solution was the old magic:
Eclipse error: Project 'X' is missing required Java
- Step (1) Remove a project from the "Java Build Path|Order and Export"
- Step (2) Return it again to the screen.
This fixed something in the database of eclipse and solved the problem.