sandbox git for checking out dart classes behavior

classes_sandbox.dart

class SuperClass {
  void hello() => print('hello');
  void world() {
    hello();
    print('world!');
    print('');
  }
}

class SubClass extends SuperClass {
  @override
  void hello() => print('hi');
}

void main() {
  print('super class:');
  final x = SuperClass();
  x.world();

  print('sub class:');
  final y = SubClass();
  y.world();
}