Dart inheritance

void main() {
  Child obj = Child();
  obj.childMethod();
  obj.parentMethod();
  obj.grandParentsMethods();
}

class GrandParents{
  void add(int a, int b){
    print (a+b);
  }
//   void add(int a, int b, int c){
//     print (a+b+c);
//   }
  void grandParentsMethods(){
    print ("This is Grand parents.");
  }
}

class Parents extends GrandParents{
  void parentMethod(){
    print("This is Parents.");
  }

}

class Child extends Parents{
//   void childMethod(int a, int b){
//     print (a-b);
//   }
  void childMethod(){
    print ("This is Child.");
  }
  Child(){
    print ("This is Constructor");
  }
}