In earlier chapters you saw how Guice's @ImplementedBy annotation is used to designate the default implementation of an interface.
Guice has another more flexible configuration mechanism, namely a Guice Module which you code yourself.
Moreover, the configuration that you place in a Guice Module takes precedence over any @ImplementedBy annotations in the code, which allows you to configure Guice to use your custom implementation instead of the default implementation. This may be useful for customisation or testing purposes.