Generic Class Hierarchies: uses a generic superclass : Generic Class Hierarchies « Generics « Java Tutorial

In a generic hierarchy, any type arguments needed by a generic superclass must be passed up the hierarchy by all subclasses.

class Gen<T> { 
  T ob;
  Gen(T o) { 
    ob = o; 
  T getob() { 
    return ob; 

class Gen2<T> extends Gen<T> {
  Gen2(T o) {

12.7.Generic Class Hierarchies
12.7.1.Generic Class Hierarchies: uses a generic superclass
12.7.2.A subclass can add its own type parameters, if needed.
12.7.3.A Generic Subclass: a nongeneric class can be the superclass of a generic subclass
12.7.4.Run-Time Type Comparisons Within a Generic Hierarchy
12.7.5.Casting within a generic class hierarchy
12.7.6.Overriding Methods in a Generic Class