What's wrong with this example of Java propert

Question

Inheritance.java

public class InheritanceExample {
  static public void main(String[] args){
    Cat c = new Cat();
    System.out.println(c.speak());

    Dog d = new Dog();
    System.out.println(d.speak());
  }
}

Animal.java

public class Animal {
  protected String sound;
  public String speak(){
    return sound;
  }
}

Cat.java

public class Cat extends Animal {
  protected String sound = "meow";
}

Dog.java

public class Dog extends Animal {
  protected String sound = "woof";
}

---

Output:

null
null

My animals cannot speak. So sad.

Answer 1

A method will look in its own class' namespace to resolve fields. While methods defined in sub-classes can look up the hierarchy to resolve fields, the same is not true for classes defined higher up in the hierarchy, i.e., super-classes won't look down the hierarchy to resolve fields [and their values]