扩展Vector是什么意思 <Object> 在java中？

Question

For example, I have a class that says

public class KeyList extends Vector<Object> {
}

but it never specifically creates a new Vector of any kind. This is part of an implementation of Eliza that I found online

Answer 1

extends means that KeyList is-a Vector . It does not (necessarily) mean that KeyList has-a Vector .

See The Java Tutorial for more, specifically What Is Inheritance? and the Inheritance section .

Answer 2

It is about inheritance: meaning that KeyList is a subclass of Vector<Object> . Essentially it means that KeyList is a modified Vector<Object> in itself. For more information, you should read Oracle's docs on inheritance.