Access subclass fields from a base class in Java

by

If you want to access properties of a subclass, you’re going to have to cast to the subclass.

if (g instanceof Sphere)
{
    Sphere s = (Sphere) g;
    System.out.println(s.radius);
    ....
}

This isn’t the most OO way to do things, though: once you have more subclasses of Geometry you’re going to need to start casting to each of those types, which quickly becomes a big mess. If you want to print the properties of an object, you should have a method on your Geometry object called print() or something along those lines, that will print each of the properties in the object. Something like this:


class Geometry {
   ...
   public void print() {
      System.out.println(shape_name);
      System.out.println(material);
   }
}

class Shape extends Geometry {
   ...
   public void print() {
      System.out.println(radius);
      System.out.println(center);
      super.print();
   }
}

This way, you don’t need to do the casting and you can just call g.print() inside your while loop.

More Related Contents:

  1. Java : If A extends B and B extends Object, is that multiple inheritance
  2. Anonymous vs named inner classes? – best practices?
  3. How do I correctly implement this code segment without getting a logic error? [closed]
  4. What’s wrong with overridable method calls in constructors?
  5. How do you find all subclasses of a given class in Java?
  6. Extends JFrame vs. creating it inside the program
  7. Can we instantiate an abstract class?
  8. Why is there no multiple inheritance in Java, but implementing multiple interfaces is allowed?
  9. What is an interface in Java?
  10. What are classes, references, and objects?
  11. Why to use Interfaces, Multiple Inheritance vs Interfaces, Benefits of Interfaces?
  12. What is the main difference between Inheritance and Polymorphism?
  13. How should I have explained the difference between an Interface and an Abstract class?
  14. How can a class have a member of its own type, isn’t this infinite recursion?
  15. Why do we assign a parent reference to the child object in Java?
  16. what is the Class object (java.lang.Class)?
  17. Is it possible to call subclasses’ methods on a superclass object?
  18. Is polymorphism possible without inheritance?
  19. Java: Static Class?
  20. Why use inheritance at all? [closed]
  21. When do I have to use interfaces instead of abstract classes? [duplicate]
  22. Advantage of Local Classes Java
  23. Private members in Java inheritance
  24. Why we should not use protected static in java
  25. Can we instantiate an abstract class directly? [duplicate]
  26. Why are constructors not inherited in java?
  27. Avoiding parallel inheritance hierarchies
  28. What are the purposes of inner classes
  29. Why can’t a Java class be declared as static?
  30. Java: Use import or explicit package / class name?

Leave a Comment