Guice provides special syntax for making an object that has the singleton scope, and is initialized to eager mode rather than lazy mode. Following is the syntax:
bind(NotificationService.class).to(SMSService.class).asEagerSingleton();
Eager singletons uncover initialization issues sooner, and guarantee end users get a reliable, smart encounter. Lazy singletons empower a quicker edit-compile-run development cycle. We can utilize the stage enum to indicate which procedure ought to be utilized.
The following table defines stage-wise use of syntax of the singleton and supported object initialize mode:
| Syntax | PRODUCTION | DEVELOPMENT |
| @Singleton | eager* | lazy |
| .asEagerSingleton() | eager | eager |
| .in(Singleton.class) | eager | lazy |
| .in(Scopes.SINGLETON) | eager | lazy |
Guice eagerly creates singleton instances only for the modules that are defined as singleton.
@SessionScoped and @RequestedScoped scope functionality and behavior is the same as Spring in Guice, and it will only be applicable when used in a web application.