java - hashmap.keyset() 会按照它们被添加到 hashmap 的顺序返回键吗？

Question

我知道 .keySet() 返回一个集合，它是无序的。

据我所知，这意味着我需要保留一个键数组列表，以便跟踪将键添加到 HashMap 中的顺序，对吗？

Answer 1

[...] 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?

是的，没错。或者，您可以使用 LinkedHashMap这是为你做的。

来自文档:

[...] 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). [...]