Question

There is some interfaces in my app and I want to create singleton class, that provides implementations of them. Like so:

public class Singleton{
    //singleton's stuff

    private Interface1 interface1Impl;
    private Interface2 interface2Impl;

    public Interface1 getInterface1(){
        return interface1Impl;
    }

    public Interface2 getInterface2(){
        return interface2Impl;
    }
}

What I’m looking for – provide same interface implementation for each class in app. With this way everything works fine, but is it a good way to achieve this?

Answer 1

Yes, it looks much like a Factory (or maybe Service Locator is more suitable in your case).

Factory is almost always a better idea than a Singleton. For instance, a Factory can work as a Singleton when you need it (lazy initialization, caching), and you can alter this behavior when you need something else (for testing, thread safety, etc).