如何基于“键"更改TreeMap中的条目顺序 [英] How to change the sequence of entries in TreeMap based on the 'Key'

问题描述

我有一个Map<String,List<UserVO>> studentsByCountry = new TreeMap<String,List<UserVO>>();

显示为:

key=CountryA , value = List<UserVO>
key=CountryB , value = List<UserVO>
key=CountryC , value = List<UserVO>

我可以重新排列此Map以便根据国家/地区的displayOrder显示.显示顺序为countryC = 1，countryB = 2& countryA = 3.我想显示为

Can I reshuffle this Map so that I display according to the displayOrder of the countries. Display order is countryC=1, countryB=2 & countryA=3. I want to display like

key=CountryC , value = List<UserVO>
key=CountryB , value = List<UserVO>
key=CountryA , value = List<UserVO>

一个选择是将sortOrderNumber附加到键上. For example 1_CountryC, 2_CountryB & 3_CountryA

One option is to append the sortOrderNumber to the key. For example 1_CountryC, 2_CountryB & 3_CountryA

我可以通过常规Java做到吗?

Can I do it via conventional Java?

推荐答案

您应使用new TreeMap<String, List<UserVO>>();

Map<String, List<UserVO>> sortedMap = new TreeMap<>(Collections.reverseOrder());
sortedMap.putAll(myMap);

灵感来自于:排序降序:Java Map

如果您想要无序地图，则应使用HashMap

Java中的TreeMap是Map接口的实现之一.它与其他实现HashMap的不同之处在于，它不同于HashMap which is unordered，TreeMap is Sorted.

TreeMap in Java is one of the implementations of the Map interface. How it differs from the other implementation HashMap is that unlike HashMap which is unordered, TreeMap is Sorted.

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