hashmap.keyset（）会按照它们添加到hashmap的顺序返回键吗？ [英] Will hashmap.keyset() return keys in the order they were added to the hashmap?

问题描述

我知道 .keySet（）会返回一个未订购的集合。

I know that the .keySet() returns a set, which is un-ordered.

据我所知，这意味着我需要保留一个数组键列表，以便跟踪键添加到hashmap的顺序，正确？

As far as I can tell, that means I need to keep an array list of keys in order to track the order in which the keys were added to the hashmap, correct?

推荐答案

[...] 这意味着我需要保留一个数组列表为了跟踪键添加到hashmap的顺序，是正确的吗？

是的，那是正确。或者，您可以使用 LinkedHashMap 这是为你做的。

Yes, that's correct. Or, you could use a LinkedHashMap which does this for you.

来自文档：

[...]此实现与HashMap的不同之处在于它维护了一个贯穿其所有条目的双向链表。此链接列表定义迭代排序，通常是将键插入到映射中的顺序（插入顺序）。 [...]

[...] This implementation differs from HashMap in that it maintains a doubly-linked list running through all of its entries. This linked list defines the iteration ordering, which is normally the order in which keys were inserted into the map (insertion-order). [...]

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