Guice allows us to define injection at the method level by annotating methods with the @Inject annotation. This is similar to the setter injection available in Spring. In this approach, dependencies are passed as parameters, and are resolved by the injector before invocation of the method. The name of the method and the number of parameters does not affect the method injection:

private NotificationService notificationService;
//Setter Injection
@Inject
public void setService(NotificationService service) {
   this.notificationService = service;
}

This could be valuable when we don't want to control instantiation of classes. We can, moreover, utilize it in case you have a super class that needs a few dependencies. (This is difficult to achieve in a constructor injection.)