Question

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Difference between static class and singleton pattern?

Which is better in Java,

implementing public static methods, like

Factory.createLoginRequest()

or implementing Singleton pattern, like

Factory.getInstance().createLoginRequest()

(Boths will return a Request object.)

Which one is better and why ?

Answer 1

from wikipedia:

Note the distinction between a simple static instance of a class and a singleton: although a singleton can be implemented as a static instance, it can also be lazily constructed, requiring no memory or resources until needed. Another notable difference is that static member classes cannot implement an interface, unless that interface is simply a marker. So if the class has to realize a contract expressed by an interface, it really has to be a singleton.