How to create Singleton Class in Java?

Answer 1

class Singleton
{

    private static Singleton single_instance = null;

    public String s;

    // private constructor restricted to this class itself
    private Singleton()
    {
        s = "I am a string part of Singleton ";
    }

    // static method to create instance of Singleton class
    public static Singleton getInstance()
    {
        if (single_instance == null)
            single_instance = new Singleton();

        return single_instance;
    }
}

// Driver Class

class Main
{
    public static void main(String args[])
    {
        // instantiating Singleton class with variable x
        Singleton x = Singleton.getInstance();

        // instantiating Singleton class with variable y
        Singleton y = Singleton.getInstance();



        // changing variable of instance x
        x.s = (x.s).toUpperCase();

        System.out.println("String from x is " + x.s);
        System.out.println("String from y is" +y.s);

        System.out.println("String from x is " + x.s);
        System.out.println("String from y is " + y.s);

    }
}