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How to make a class singleton in Java using Singleton Design Pattern ?.

Program to demonstrate how to make a class singleton in Java using Singleton Design Pattern.
package com.hubberspot.designpattern.creational.singleton;

//Steps to make a class Singleton in nature :-

//   1. Create a class by name say SingletonClass 
public class SingletonClass {

    //   2. Create a private default constructor of the
    //      class created above in step 1.

    private SingletonClass() { 


    //   3. Create a private static variable of type class
    //      created in step 1 itself. It should be private,
    //      static and gets reference to instance of class itself.

    private static SingletonClass SINGLETON_INSTANCE = 
            new SingletonClass();

    //   4. Create a static accessor method which always 
    //      return us back the same instance created in 
    //      step 3. The name of the method could be
    //      according to good naming convention as : 
    //      getInstance()

    public static SingletonClass getInstance() {
        return SINGLETON_INSTANCE;
    //   5. There should not be any method or constructor
    //      which creates another object of SingletonClass.

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