题解 | #字符统计#

这道题目的核心地方时学会java中对HashMap进行排序。

1. 将HashMap中Entry元素放入List中

2. 对List使用Collections.sort（）方法进行排序，并且重写comparator方法

3. 输出排序后的List结果

   import java.util.*;
   public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            String line = sc.nextLine().trim();
            HashMap<Character,Integer> hm = new HashMap<>();
            for (int i = 0; i < line.length(); i++) {
                if(hm.containsKey(line.charAt(i))){
                    hm.put(line.charAt(i),hm.get(line.charAt(i))+1);
                }else {
                    hm.put(line.charAt(i),1);
                }
            }
            LinkedList<Map.Entry<Character,Integer>> list = new LinkedList<>(hm.entrySet());
            Collections.sort(list, new Comparator<Map.Entry<Character, Integer>>() {
                @Override
                public int compare(Map.Entry<Character, Integer> o1, Map.Entry<Character, Integer> o2) {
                    if(o1.getValue()== o2.getValue()){
                        return o1.getKey().compareTo(o2.getKey());
                    }else {
                        return o2.getValue()-o1.getValue();
                    }
                }
            });
            StringBuffer sb = new StringBuffer();
            for (int i = 0; i < list.size(); i++) {
              sb.append(list.get(i).getKey());
            }
            System.out.println(sb.toString());
   
        }
    }
   }