如何打印出 HashMap<String, String> 的内容根据其值升序排列? [英] How print out the contents of a HashMap<String, String> in ascending order based on its values?

问题描述

我有这个 HashMap 我需要根据其中包含的 values 以升序打印出来(不是钥匙).

I have this HashMap that I need to print out in ascending order according to the values contained in it (not the keys).

但是我打印出来的顺序似乎是随机的.

But the order when I print it out is seemingly random.

以升序打印出来的最佳方式是什么?

What's the best way to print it out in ascending value order?

Map<String, String> codes = new HashMap<String, String>();

codes.put("A1", "Aania");
codes.put("X1", "Abatha");
codes.put("C1", "Acathan");
codes.put("S1", "Adreenas");

换句话说，上面的例子应该是这样打印出来的:

In other words, the example above should print out as this:

A1, Aania
X1, Abatha
C1, Acathan
S1, Adreenas

推荐答案

您无法仅从 HashMap 类中做到这一点.

You aren't going to be able to do this from the HashMap class alone.

我会使用 Map<String, String>代码，构造TreeMap的反向映射；reversedMap 您将 codes Map 的值映射到键(这将要求您的原始 Map 具有从键到值的一对一映射).由于 TreeMap 提供了迭代器，它以升序键顺序返回条目，这将为您提供您想要的顺序(按值排序)的第一个映射的值/键组合.

I would take the Map<String, String> codes, construct a reverse map of TreeMap<String, String> reversedMap where you map the values of the codes Map to the keys (this would require your original Map to have a one-to-one mapping from key-to-value). Since the TreeMap provides Iterators which returns entries in ascending key order, this will give you the value/key combination of the first map in the order (sorted by values) you desire.

Map<String, String> reversedMap = new TreeMap<String, String>(codes);

//then you just access the reversedMap however you like...
for (Map.Entry entry : reversedMap.entrySet()) {
    System.out.println(entry.getKey() + ", " + entry.getValue());
}

有几个集合库(commons-collections、Google Collections 等)具有类似的双向 Map 实现.

There are several collections libraries (commons-collections, Google Collections, etc) which have similar bidirectional Map implementations.

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