Question

Consider the following code in Python:

class A(object):
    CLASS_ATTRIBUTE = 42

    def f(self):
        return "CLASS_ATTRIBUTE: %d" % self.CLASS_ATTRIBUTE

class B(A):
    CLASS_ATTRIBUTE = 44

Now A().f() and B().f() return "CLASS_ATTRIBUTE: 42" and "CLASS_ATTRIBUTE: 44" respectively.

How can I achieve a similar effect in Java? I want a CLASS_ATTRIBUTE field to be initialized statically and redefined in the inherited class but the f method should be only defined in the base class.

Answer 1

I’m not sure if you meant “statically” literally or not, but here’s a brief example of how inheritance at it’s most basic form looks in Java. Note that using a getter method to access the variable is a better idea for several reasons — this is just an example.

public class Dog {
  protected String whatISay = "Woof!";
  public void speak(){
    System.out.println(whatISay);
  }
}


public class Poodle extends Dog {
  public Poodle(){
    whatISay = "Yap!";
  }
}


public class Main {
  public static void main(String[] args){
    Poodle fluffy = new Poodle();
    fluffy.speak();
    Dog dog = new Dog();
    dog.speak();
  }
}

Yap!
Woof!