Hi,

A class whose number of instances that can be instantiated is limited to one is called a singleton class. Thus, at any given time only one instance can exist, no more.

public class Single {
    private static Single a;

    private Single() {

    }

    public static Single getSingle() {
        if (a == null) {
            a = new Single();
        }
        return a;
    }

    public static void main(String... s) {
        Single a1 = Single.getSingle();
        Single a2 = Single.getSingle();
        System.out.println(a1);

        System.out.println(a2);
    }

}

This program give the out put as-

samar.Single@3e25a5
samar.Single@3e25a5

Thanks.