在HashMap或LinkedList中制作嵌套类的原因是什么？ [英] What is the reason for making a nested class static in HashMap or LinkedList?

问题描述

在大多数情况下，我已经看到嵌套类是 static 。

In most of the cases I've seen that nested classes are static.

让我们举个例子条目类中 HashMap

static class Entry<K,V> implements Map.Entry<K,V> {
    final K key;
    V value;
    Entry<K,V> next;
    final int hash;

    .....
    .....
}

或条目 LinkedList

private static class Entry<E> {
    E element;
    Entry<E> next;
    Entry<E> previous;

    .....
    .....
}

到目前为止，关于嵌套类的知识是：

What I know so far about nested class is:

- A non-static nested class has full access to the members of the class 
  within which it is nested.

- A static nested class cannot invoke non-static methods or access non-
  static fields

我的问题是，在HashMap或LinkedList中创建嵌套类的原因是什么？

My question is, what is the reason for making a nested class static in HashMap or LinkedList?

Update 1：

Following the already answer link I got an answer - Since And since it does not need 
access to LinkedList's members, it makes sense for it to be static - it's a much 
cleaner approach.

Also as @Kayaman pointed out: A nested static class doesn't require an instance of 
the enclosing class. This means that you can create a HashMap.Entry by itself, 
without having to create a HashMap first (which you might not need at all).

我认为这两点都回答了我的问题。感谢您的所有输入。

I think both these points answered my question. Thanks all for your input.

推荐答案

嵌套静态类不需要包含类的实例。这意味着你可以自己创建一个 HashMap.Entry ，而不必先创建一个 HashMap 根本不需要）。

A nested static class doesn't require an instance of the enclosing class. This means that you can create a HashMap.Entry by itself, without having to create a HashMap first (which you might not need at all).

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