Singleton Design Pattern Example Program

Singleton Design pattern will allow only one object per Class(JVM).

Before Writing Singleton Design pattern you should follow these steps.

#1). create an instance as static and return type as The same class, and it should be assigned as null.

private static Singletonn instance = null;

#2). "Create a Constructor as private" to deny the creation of object from other class.

private Singletonn(){

         

    }

?

#3). Write a static method to create object for our class.It should be Once for a class.

?#4). At last return the class Object.

public static Singletonn getInstance(){

}

#4). At last return the class Object.


Here We are creating the object once only not again and again.The first time created object is returning again when you called.

package javabynataraj.basic;

class Singletonn {

    private static Singletonn instance = null;

    private Singletonn(){

         

    }

    public static Singletonn getInstance(){

        if(instance==null){

            instance = new Singletonn();

        }

        return instance;

    }

}

public class Singleton{

    public static void main(String[] args) {

        System.out.println("before calling ...");

        System.out.println(Singletonn.getInstance());

        System.out.println("Once Called");

        System.out.println(Singletonn.getInstance());

        System.out.println("Second time called");

    }

}

?