如何打印出HashMap的内容< String，String>基于其值的升序？ [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 ，需要按照其中包含的 值升序打印出来（ 不是键 ）。

但我打印出来的顺序看起来是随机的。 b
$ b

以 升序价格顺序打印出来的最佳方式

？

  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，上面的例子应该打印出来：

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

解决方案

您无法单独从HashMap类中完成此操作。

我会将地图< String，String>代码，构造一个反向映射 TreeMap< String，String> invertMap 在那里你映射代码映射到键的值（这将要求你的原始Map有一个一对一的映射键到值）。由于TreeMap提供的迭代器按照递增的键顺序返回条目，因此这会给你按照你想要的顺序（按值排序）的第一个映射的值/键组合。

 地图< String，String> invertMap = new TreeMap< String，String>（codes）; 
 
 //然后你只需访问反向映射，不过你喜欢... 
 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。

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

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

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");

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

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

解决方案

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

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());
}

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

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