How do I find where an instance of a Java singleton is created?

Question

In a large, complex program it may not be simple to discover where in the code a Singleton has been instantiated. What is the best approach to keep track of created singleton instances in order to re-use them?

Regards, RR

Answer 1

A Singleton usually has a private constructor, thus the Singleton class is the only class which can instantiate the one and only singleton instance.

Answer 2

It's the responsibilty of singleton class developer to make sure that the instance is being reused on multiple calls.

As a user, you shouldn't worry about it.

class Singelton
{
    private static Singelton _singelton = null;

    private Singelton()
    {

    }

    // NOT usable for Multithreaded program
    public static Singelton CreateMe()
    {
        if(_singelton == null)
            _singelton = new Singelton();
        return _singelton;        
    }
}

Now, from anywhere in your code, you can instantiate Singelton, how many times you like and each time assign it to different reference. but c'tor is called ONLY once.