如何确保在Java中遍历HashMap时无法更改密钥的顺序？

How to make sure the key's order can not be changed when traversing a HashMap in Java?

本问题已经有最佳答案，请猛点这里访问。

例如，我输入3个字符串：Hagzou Hugzou Jigxng作为HashMap的键，

但是当我按键遍历HashMap时，订单已被更改：Hugzou Hagzou Jigxng。

是否可以确保在输出密钥时无法更改订单？

像这样：

输入：Hagzou Hugzou Jigxng ###

输出：Hagzou Hugzou Jigxng

多谢！

这是我的代码：

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HashMap< String, Integer > distance = new HashMap< String, Integer >();
Scanner input = new Scanner(System.in);
while (true) {
String city = input.next();
if (city.equals("###"))
break;
distance.put(city, null);
}
for (String city : distance.keySet()) {
System.out.println(city);
}

相关讨论

您可以使用LinkedHashMap：

Hash table and linked list implementation of the Map interface, with
predictable iteration order. 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). Note that insertion order is not affected if a key
is re-inserted into the map. (A key k is reinserted into a map m if
m.put(k, v) is invoked when m.containsKey(k) would return true
immediately prior to the invocation.)

换句话说 - 虽然LinkedHashMap有一种通过其哈希码访问条目的方法，如常规HashMap，它还维护一个双向链表，并维护项插入的顺序。这样，当您使用其迭代器时，您将按照插入它们的顺序获取项目。