main.dart

class Employee {
  
  Employee()
  {
    print("inside default");
  }
  // Person does not have a default constructor;
  // you must call super.fromJson(data).
  Employee.fromJson(Map data){
    print('in Employee');
  }
}

main() {
  var emp  = new Employee.fromJson({});
  var emps = new Employee(); 
}