Design Pattern: Singleton design pattern

 In software engineering, the singleton pattern is a design pattern that restricts the instantiation of a class to one object. This is useful when exactly one object is needed to coordinate actions across the system

There are only two points in the definition of a singleton design pattern,

1.     there should be only one instance allowed for a class and

2.     we should allow global point of access to that single instance.

// "Singleton"

    class Singleton

    {

        private static Singleton instance;

        // Note: Constructor is 'protected'

        protected Singleton()

        {

        }

        public static Singleton Instance()

        {

            // Use 'Lazy initialization'

            if (instance == null)

            {

                instance = new Singleton();

            }

            return instance;

        }

    }