按数值降序排列哈希图键 [英] Sort Hashmap keys by numerical value descending order

问题描述

如何通过数值对 HashMap 键进行排序？目前，在自然排序中，它看起来像这样：

  1 10 13 2 26 29 
  

我希望它看起来像这样：

  29 26 13 10 2 1 
  

有什么想法？

HashMap 无法排序。如果您需要排序的密钥，请查看 TreeMap的 。为了获得您想要的颠倒顺序，您必须提供自定义 Comparator ：

  class ReversedOrdering implements比较<整数> {
 public int compare（Integer lhs，Integer rhs）{
 //比较反转
 return rhs.compareTo（lhs）; 
} 
} 
  

编辑跨越 Collections.reverseOrder（） ，它可以做你想做的事情：它给你一个 Comparator ，它颠倒实现对象的自然顺序可比这节省了您自己编写比较器的麻烦。

How can I sort HashMap keys by their numerical value? Currently, in the natural ordering it looks like this:

1 10 13 2 26 29

I want it to look like this:

29 26 13 10 2 1

Any ideas?

解决方案

A HashMap cannot be sorted. If you require sorted keys, take a look at the TreeMap. In order to get the reversed ordering you want, you would have to provide a custom Comparator:

class ReversedOrdering implements Comparator<Integer> {
    public int compare(Integer lhs, Integer rhs) {
        // compare reversed
        return rhs.compareTo(lhs);
    }
}

Edit I just stumbled across Collections.reverseOrder() which does just what you want: It gives you a Comparator that reverses the natural ordering of objects that implement Comparable. This saves you the hassle of writing a comparator yourself.

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