How To Fix Eclipse Resource Out of Sync
If you ever edited an Eclipse project outside of Eclipse, then you might have experienced the “Resource out of sync with the file system” error. Sadly the error message does not give you any hints on how to fix it and a simple Google search does not have any helpful links on the first page. This is quite surprising, as the fix is quite simple. Just press the F5 key to refresh your project and you are done! The same can also be accomplished by right clicking the project node in Package Explorer and locating the Refresh option (HINT: It is in the middle) in the popup menu.
This also fails if you have sources generated outside of Eclipse and it’s driving me crazy.
You can also enable auto-refresh.
Preferences->general->workspace …
thank you for the very useful message