A private constructor can be called outside its class but how??????

You cant invoke private constructor from Outside the clas.
We declare constrcutor as private when we want to restrict user from creating objects..

Normallyin this case we create static method in class which will return the Class Object

public class A
{ 
 private A()
 {
 }
 public static A GetA()
 {
  return new A();
 }
}
.
.
.
.
Main()
{
 A a=A.getA();
}

Hope this helped, check this is correct answer