为什么LinkedHashSet< E>扩展HashSet< e>并实现Set< [英] Why does LinkedHashSet<E> extend HashSet<e> and implement Set<E>

问题描述

今天打开了LinkedHashSet源代码，发现了一些有趣的事情：

Opened a LinkedHashSet source code today and found some interesting thing:

public class LinkedHashSet<E>
    extends HashSet<E>
    implements Set<E>, Cloneable, java.io.Serializable {

：为什么当HashSet已经是Set时，它们需要extends HashSet和implements Set？

The question is: why do they need both "extends HashSet" and "implements Set" when HashSet already is the Set?

推荐答案

问Josh Bloch，他告诉我这是一个错误。他以前很久以前就想过，在那里有一些价值，但他从看到光。显然，JDK维护者没有认为这是值得支持的。

I've asked Josh Bloch, and he informs me that it was a mistake. He used to think, long ago, that there was some value in it, but he since "saw the light". Clearly JDK maintainers haven't considered this to be worth backing out later.

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