What is a singleton class?How do you writer it? Tell examples?

A class which must create only one object (ie. One instance) irrespective of any number of object creations based on that class.

Steps to develop single ton class:-

1.Create a Private construcor, so that outside class can not access this constructor. And declare a private static reference of same class

2.Write a public Factory method which creates an object. Assign this object to private static Reference and return the object

Sample Code:-

class SingleTon


private static SingleTon st=null;

private SingleTon()


System.out.println(“\nIn constructor”);


public static SingleTon stfactory()


if(st==null) st=new SingleTon();

return st;





For complete Example of Singleton design pattern click here