Java inheritane of attributes and methods

quiz_03.java

/*
The question is simply: what is the output?
Extra: what is `instance.z` after line 8?
*/

public class TestQuestion1 {
  public static void main(String[] args) {
    SuperCls instance = new SubCls();
  }
}

class SuperCls {
  protected Integer x = 1;
  protected Integer y = 3;

  public SuperCls() {
    System.out.println("super constructor");
    b();
  }

  public void b() {
    System.out.println("super b");
    System.out.printf(String.format("x = %d, y = %d\n", x, y));
  }
}

class SubCls extends SuperCls {
  protected Integer x = 2;
  public Integer z = 5;

  public SubCls() {
    y = 4;
    System.out.println("sub constructor");
    b();
  }

  @Override
  public void b() {
    super.b();
    System.out.println("sub b");
    System.out.printf(String.format("x = %d, y = %d\n", x, y));
  }
}

Solution: https://gist.github.com/mverleg/0f03c8850c08b264471e690d86a319aa