Eclipse can't find / load main class

Question

My Eclipse (Indigo) was running just fine. I created a simple class Hello. It is placed in package cont in the folder ch13. However

Answer 1

• Removing the Run Configuration

  Sometimes I have a similar problems in some pre-release versions of eclipse. For fix the error, I delete the Run Configuration. You can find that in menu Run, Run Configurations...

  Then I launch the app with Alt+Shift+X, then J. If this don't work, Ctrl+F11.

• Deleting the .metadata directory

  In another way, the configuration settings for your current workspace may are corrupted. Those settings are in the .metadata directory in your current workspace ¹. In that case, there is no other choice than delete the directory:

  1. Close eclipse.
  2. Delete the .metadata directory.
  3. Start eclipse.
  4. Import the projects.
  5. Run the project again.

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Notes

1. You will see that directory with File > Switch Workspace > Other...