Question

A straight forward implementation of a Singleton pattern without using Metaclass:

class A{
    static final instance = new A()
    private A(){}

    static getInstance(){return instance}
} 

Why is it that the private constructor is not respected by groovy? Though one can tell by intuition that it is a singleton looking at the pattern, Unlike java, such an implementation does not restrict the programmer from creating a new instance of this class using new A() outside the scope of this class. So shouldn’t this be considered as a flaw in its implementation?

Answer 1

You can replace the code above with:

@Singleton
class A{
} 

and access the singleton instance via:

A singleton = A.instance