Dart编程实例 - 实现多个接口

void main() {

   Calculator c = new Calculator();

   print("The gross total : ${c.ret_tot()}");

   print("Discount :${c.ret_dis()}");

}  

class Calculate_Total {

   int ret_tot() {}

}  

class Calculate_Discount {

   int ret_dis() {}

}

class Calculator  implements Calculate_Total,Calculate_Discount {

   int ret_tot() {

      return 1000;

   }

   int ret_dis() {

      return 50;

   }

}