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

Why can't you do just

public class SingletonSandBox {

    private static SingletonSandBox instance = new SingletonSandBox();

    private SingletonSandBox(){
    }

    public static SingletonSandBox getInstance(){
        return instance;
    }

}

and test

public static void main(String[] args) {

        SingletonSandBox sss1 = SingletonSandBox.getInstance();

        SingletonSandBox sss2 = SingletonSandBox.getInstance();

        System.out.println(sss1 == sss2);

}

As I know this is thread-safe and shorter than using static block. Again static field declaration is read earlier comparing to static block by the runtime.