Abstract methods, nullable, non nullable and default parameters

main.dart

main (){}

abstract class A {
 
  void listen({
    bool isOk,
    required String isBad,
  });
}

class A1 extends A {
  @override
  void listen({bool? isOk, String? isBad}) {}
}

class A2 extends A {
  @override
  void listen({bool isOk = true, String isBad = "Really Bad"}) {}
}