This example shows inheritance in Dart

main.dart

class Product{
  String _name;
  num _price;
  String _expDate;
  
  Product(this._name,this._price,this._expDate);
  
  void printDetails(){
    print('Name: $_name');
    print('Price: $_price');
    print('Expire: $_expDate');
    
  }
}

class Beverage extends Product{
  
num _liters;
  String _type;
  
  Beverage(String name, num price, String expDate, this._liters,this._type):
  super(name,price,expDate);
  
  void beverageDetails(){
    printDetails();
    print('Liters: $_liters');
    print('Type: $_type');
  }
  
}

void main(){
  var drink = Beverage('Cola', 1.50, '1/1/2022', 1, 'soft drink ');
  drink.beverageDetails();
}