Dart "extends" and "implements" interfaces

Interfaces.dart

abstract class Person {
  String get name;
  int get age;
  
  void speak(String name, int age);
  void walk() {
    print('walk');
  }
}

class Male extends Person {
  final String name;
  final int age;
  
  Male(this.name, this.age);
  
  @override
  void speak(String name, int age) {
    final voice;
    
    if (age >= 15) {
      voice = 'man';
    } else {
      voice = 'boy';
    }
    
    print('$name speaks with $voice voice');
  }
  
}

class Female implements Person {
  final String name;
  final int age;
  
  Female(this.name, this.age);
  
  @override 
  void speak(String name, int age) {
    final voice;
    
    if (age >= 18) {
      voice = 'woman';
    } else {
      voice = 'girl';
    }
    
    print('$name speaks like a $voice');
  }
  
  @override 
  void walk() {
    print('walks slow');
  }
}

void main() {
  final abdulloh = Male('Abdulloh', 15);
  final kamola = Female('Kamola', 17);
  
  print(abdulloh.name);
  print(abdulloh.age);
  
  abdulloh.speak(abdulloh.name, abdulloh.age);
  
  print(kamola.name);
  print(kamola.age);
  
  kamola.speak(kamola.name, kamola.age);
  kamola.walk();
}