Examining Classes

Finding Superclasses

Because the Java programming language supports inheritance, an application such as a class browser must be able to identify superclasses. To determine the superclass of a class, you invoke the getSuperclass method. This method returns a Class object representing the superclass, or returns null if the class has no superclass. To identify all ancestors of a class, call getSuperclass iteratively until it returns null.

The program that follows finds the names of the Button class's ancestors by calling getSuperclass iteratively.

import java.lang.reflect.*;
import java.awt.*;

class SampleSuper {

   public static void main(String[] args) {
      Button b = new Button();
      printSuperclasses(b);
   }

   static void printSuperclasses(Object o) {
      Class subclass = o.getClass();
      Class superclass = subclass.getSuperclass();
      while (superclass != null) {
         String className = superclass.getName();
         System.out.println(className);
         subclass = superclass;
         superclass = subclass.getSuperclass();
      }
   }
}

The output of the sample program verifies that the parent of Button is Component, and that the parent of Component is Object:

java.awt.Component
java.lang.Object

Examining Classes