Creating a Generic Class

Java Tutorials - Herong's Tutorial Examples - Version 7.03, by Dr. Herong Yang

Java Tutorials - Herong's Tutorial Examples

∟Generic Classes and Parameterized Types

∟Creating a Generic Class

This section describes how to create a generic class by declaring type parameters and using them as 'Type Variable' types within the scope of the class.

When creating a generic class, you need to know how to declare a type parameter and how to use it as a "Type Variable" type:

1. Declaring type parameters - When declaring a generic class, you need to provide type parameter enclosed in angle brackets after the class name. Examples are listed below:

   class ObjectRegistry<T> {}
   class HashMap<K,V> {}

2. Using the type parameter - When a type parameter is declared, it becomes a "Type Variable" reference type that can be used within the scope of the class. Examples are listed below:

class ObjectRegistry<T> {
   public void register(T item) {}
}

class Box<T> {
    private T t;
    public void set(T t) { this.t = t; }
    public T get() { return t; }
}

In the example above, "T" becomes a special reference type called "Type Variable" type which is used to declare local variables like "t".

Last update: 2014.

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