hashmap键集自动排序 [英] hashmap keyset automatically sorted

问题描述

  HashMap< String，String []> content = new HashMap< String，String []>（）; 
 
 content.put（Help，new String [] {About}）; 
 content.put（View，new String [] {Grid}）; 
 content.put（File，new String [] {Import，Export}）; （String key：content.keySet（））{
 System.out.println（key）; 
 
 
} 
  

以上代码记录：

 查看
帮助
文件
  

为什么这样排序？

解决方案

1. 迭代次序。当添加新元素时，它可以（甚至会）完全改变。

4. LinkedHashMap将按照条目放入地图的顺序进行迭代
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来源

    HashMap<String, String[]> content = new HashMap<String, String[]>();

    content.put("Help", new String[]{"About"});
    content.put("View", new String[]{"Grid"});
    content.put("File", new String[]{"Import", "Export"});

    for(String key : content.keySet()){
        System.out.println(key);
    }

The above code logs:

View
Help
File

But why is this sorted?

解决方案

1. HashMap makes absolutely no guarantees about the iteration order. It can (and will) even change completely when new elements are added.

2. LinkedHashMap will iterate in the order in which the entries were put into the map

Source

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