The Google Java Style Guide §6.1 requires that a method is marked with the @Override annotation whenever it is legal. This includes a class method overriding a superclass method, a class method implementing an interface method, and an interface method respecifying a superinterface method.

Exception: @Override may be omitted when the parent method is @Deprecated. If the flag -XepOpt:MissingOverride:IgnoreInterfaceOverrides=true is used, @Override can be omitted for an interface method respecifying a superinterface method.