question: public synchronized IUser editUserName ( final IUser user , final String userName ) throws CouldntSaveDataException { Preconditions . checkNotNull ( user , "IE02723: user argument can not be null" ) ; Preconditions . checkNotNull ( userName , "IE02724: userName argument can not be null" ) ; if ( ! users . contains ( user ) ) { throw new IllegalStateException ( "IE02725: User is not known to the user management." ) ; } if ( containsUserName ( userName ) ) { throw new IllegalStateException ( "IE02726: User name is already in use by another user." ) ; } final IUser newUser = provider . editUserName ( user , userName ) ; for ( final IUserManagerListener listener : listeners ) { try { listener . editedUser ( newUser ) ; } catch ( final Exception exception ) { CUtilityFunctions . logException ( exception ) ; } } return newUser ; }
target:  Edits a users user name to something else.