Resource out of sync with the file system

Root cause of 'Resource out of sync with the file system'

If the file was modified outside of the Eclipse then it can cause Resource out of sync or some files were added of removed from outside of the Eclipse.
This says that the changes done outside of eclipse is not reflected in the eclipse. To sync the same below are the step to be followed

Solution for 'Resource out of sync with the file system'

1. Right click on the file or the whole project from within eclipse.
2. Click Refresh
3. Now try to open the file in eclipse again.

There is also an alternative

Go to Windows - > Preferences -> Click on General - > Go to Workspace and check the box ' Refresh Automatically' this problem will never occur