在 HashMap 或 LinkedList 中将嵌套类设为静态的原因是什么? [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，我看到嵌套类是static.

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

以HashMap

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

    .....
    .....
}

或LinkedList

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

    .....
    .....
}

到目前为止我对嵌套类的了解是:

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 中将嵌套类设为静态的原因是什么?

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

更新 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.感谢大家的投入.

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

推荐答案

嵌套的静态类不需要封闭类的实例.这意味着您可以自己创建 HashMap.Entry，而无需先创建 HashMap(您可能根本不需要).

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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