Java-to-Dart codelab: Bicycle example

main.dart

class Bicycle {
  int cadence;
  // Change speed to private(_speed), it is also available in the main method.
  int _speed = 0;
  int get speed => _speed;
  int gear;

  Bicycle(this.cadence, this.gear);
  
  @override
  String toString() => 'Bicycle : $_speed mph';
  
  void applyBrake(int decrement) {
    _speed -= decrement;
  }
  
  void speedUp(int increment) {
    _speed += increment;
  }
}

void main() {
  var bike = Bicycle(2, 1);
  print(bike);
  print(bike.speed);
  print(bike._speed); // <= It's strange.
  
  bike.speedUp(20);
  print(bike.speed);
  print(bike._speed);
}