Singleton : Approach2

class Approach2
{
    private static Approach2 a2 = null;
    private Approach2()
    {    }
    public static Approach2 getA2()
    {
        if( a2 == null)
        {
            a2 = new Approach2();
        }
        return a2;  }
}
public class Tests2 {

    public static void main(String[] args)
    {
        Approach2 a1 = Approach2.getA2();
        Approach2 a2 = Approach2.getA2();
        Approach2 a1000 = Approach2.getA2();
    }
}