根据值然后键对HashMap进行排序?

问题描述

可能的重复:
如何对地图进行排序<键、值>关于 Java 中的值?

我有一个 HashMap 类型:

I have a HashMap of the type:

HashMap<String, Integer> h = new HashMap<String, Integer>();

HashMap 包含一个字符串列表，而 Integer 是一个计数器，用于计算找到该字符串的次数.我想做的是根据整数对 HashMap 进行排序，然后根据字符串的字母顺序.

The HashMap contains a list of Strings and the Integer is a counter for the number of times that String has been found. What I would like to be able to do is sort the HashMap based on the Integers, then on the alphabetical order of the Strings.

目前我正在记录一个单词的最大出现次数(名为 max 的变量)并显示如下值:

At the moment I am keeping a record of the largest occurrence of a word (variable named max) and displaying the values as follows:

public void print(){
    while(max > 0){
       for (String key : h.keySet()){
           if(h.get(key) == max){
               System.out.println(key + " " + h.get(key));
           }
       }
       max--;
    }
}

它不按字母顺序对值进行排序，它也访问 HashMap max*h(size) 次.

Which doesn't sort the values alphabetically, also it accesses the HashMap max*h(size) times.

什么是更好的解决方案?

What is the better solution?

推荐答案

这是一个 Comparator，它使用 Comparable 键对 Map.Entry 对象进行排序和价值观:

Here's a Comparator that sorts Map.Entry objects with Comparable keys and values:

public class ValueThenKeyComparator<K extends Comparable<? super K>,
                                    V extends Comparable<? super V>>
    implements Comparator<Map.Entry<K, V>> {

    public int compare(Map.Entry<K, V> a, Map.Entry<K, V> b) {
        int cmp1 = a.getValue().compareTo(b.getValue());
        if (cmp1 != 0) {
            return cmp1;
        } else {
            return a.getKey().compareTo(b.getKey());
        }
    }

}

您将所有地图条目放入一个列表中，然后对其进行排序:

You'd put all of the map entries into a list and then sort that:

List<Map.Entry<String, Integer>> list = new ArrayList<Map.Entry<String, Integer>>(h.entrySet());
Collections.sort(list, new ValueThenKeyComparator<String, Integer>());

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