java first citizen class

it_cannot_be.java

interface Do {
  String do();
}

// possible case
class DoSomething {
  String do(Do do) {
    // it can be
    return do.do();
  }
}

// impossible case
class DoSomething2 {
  String do(Do do) {
    // java cannot be done this
    return do.do() = () -> {
      String ret = super.do();
      return "Impossible case : " + ret;
    }
  }
}

class DoSomething3 {
  String do(Do do) {
    return do.do2() = () -> {
      String ret = do.do();
      return "Impossible case2 : " + ret;
    }
  }
}

class Main {
  public static void main(String[] args) {
    String value1 = new DoSomething.do(() -> "Hello World"); // value1 = Hello World
    String value2 = new DoSonething2.do(() -> "Hello World2"); // expect value2 = Impossible case : Hello World2, but it cannot be
    String value3 = new DoSonething3.do(() -> "Hello World3"); // expect value3 = Impossible case2 : Hello World3, but it cannot be
  }
}