Probably everyone working with Eclipse knows the following message that shows up when a file that belongs to the Eclipse workspace is changed outside of Eclipse:
Resource is out of sync with the file system: '<Path>'
Press 'F5' or select File > Refresh to refresh the file.
Checking the “Refresh automatically” under Preferences -> Workspace helps to avoid this message. In case a file is now already open in Eclipse when changed a dialogue shows up asking if the file should be refreshed. If the file was closed in Eclipse when it is changed outside it is refreshed silently and contains the proper content when opened. This is probably wanted in 99% of all usecases.