Singleton Design Pettarn - Details Explaination

What is singleton design pattern ?

Singleton design pattern allows programmer to create only one instance for a class for whole life cycle of process. In this case if developer tries to get new instance of class, he/she will get the same instance of the class which was created once.

Way of Implementation 
To implement singleton design pattern we must have to make all the constructor of the class private, so that developers can not create new instance of the class directly (Developer will not have control to create object of class).
There must be a static  method in class which will be called by developer to obtain the singleton object.