为什么我们不能在Map（Java）上使用Iterator？ [英] Why can't we use Iterator on a Map(Java)?

问题描述

据我所知，要迭代 Map ，我需要使用 entrySet（）方法然后使用结果 Set 上的 Iterator 。我觉得问题可能很愚蠢，但是， Map 是如何完全实现的，以便直接使用 Iterator 是不可能的？据我所知， Map 不是一个集合， Iterator 是用于集合的。但从逻辑上讲，不是 Map 也是一个键值对的集合（虽然它没有实现集合接口）？

I understand that to iterate through a Map, I need to use the entrySet() method and then use the Iterator on the resultant Set. I feel the question might be silly, but, how is the Map exactly implemented so that using an Iterator on it directly isn't possible? As far as I understand, Map isn't a collection, and Iterator is meant to be used over a collection. But logically, isn't Map also a collection of key-value pair(though it doesn't implement the Collection interface)?

推荐答案

AFAIK，您不能直接迭代Map，因为Map支持三种类型的迭代并没有明确的理由选择其中一个。做等效的 entrySet（）。iterator（）可能是合理的，但这不是做出的选择。

AFAIK, You can't iterate over a Map directly because there are three types of iteration that a Map supports and there was no clear reason to choose one of the other. Doing the equivalent entrySet().iterator() may have been reasonable, but it's not the choice which was made.

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