Generic Class Hierarchies

A generic class can act as a superclass or be a subclass. In a generic hierarchy, any type arguments needed by a generic superclass must be passed up the hierarchy by all subclasses.

Using a Generic Superclass

 
class MyClass<T> {
  T ob;
  MyClass(T o) {
    ob = o;
  }
  T getob() {
    return ob;
  }
}
class MySubclass<T, V> extends MyClass<T> {
  V ob2;

  MySubclass(T o, V o2) {
    super(o);
    ob2 = o2;
  }

  V getob2() {
    return ob2;
  }
}
public class Main {
  public static void main(String args[]) {
    MySubclass<String, Integer> x = new MySubclass<String, Integer>("Value is: ", 99);
    System.out.print(x.getob());
    System.out.println(x.getob2());
  }
}

A Generic Subclass

It is perfectly acceptable for a non-generic class to be the superclass of a generic subclass.

 
class MyClass {
  int num;

  MyClass(int i) {
    num = i;
  }

  int getnum() {
    return num;
  }
}
class MySubclass<T> extends MyClass {
  T ob;
  MySubclass(T o, int i) {
    super(i);
    ob = o;
  }
  T getob() {
    return ob;
  }
}
public class Main {
  public static void main(String args[]) {
     MySubclass<String> w = new MySubclass<String>("Hello", 4);
    System.out.print(w.getob() + " ");
    System.out.println(w.getnum());
  }
}

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