How to write a Singleton in proper manner?

Question

Today in my interview one interviewer asked me to write a Singleton class. And i gave my answer as

public class Singleton {

    private static Singleton re         


        

Answer 1

You can do

public enum Singleton {
    INSTANCE;
}

and for a utility class which has no instances

public enum Utility {
     ;

     public static void method();
}