main.dart

class Class1 {
  static Class1 instance = new Class1();
  int i = 0;
}

class Class2 {
  void set i(int val) {
    Class1.instance.i = val;
  }

  int get i {
    return Class1.instance.i;
  }
}

void main() {
  Class1 c1 = Class1.instance;
  Class2 c2 = new Class2();

  for (int i = 0; i < 5; i++) {
    print('hello ${c1.i++}');
  }

  print('c2 value ${c2.i}');
}