Java使用HashMap统计字符串中每个字符出现的次数

简易多Debug看看 其实很简单 需要排序只需要将HashMap改为TreeMap即可
package com.czie.iot1913.lps.Map.MapTest00;

import java.util.HashMap;
import java.util.Scanner;
import java.util.Set;

/**
 * @author 1944900433@qq.com
 * @date 2022-03-20 22:05
 */
public class Test01 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入一个字符串：");
        String line = sc.nextLine();
        HashMap<Character,Integer> hm = new HashMap<Character,Integer>();
        for (int i = 0; i < line.length(); i++) {
            //char charAt(int index)
            //返回指定索引的 char价值。
            char key = line.charAt(i);

            Integer value = hm.get(key);
            if (value==null){
                hm.put(key,1);
            }else {
                value++;
                hm.put(key,value);
            }
        }

        StringBuilder sb = new StringBuilder();
        Set<Character> keyset = hm.keySet();
        for (Character key:keyset){
            Integer value = hm.get(key);
            sb.append(key).append("(").append(value).append(")");
        }
        String result = sb.toString();
        System.out.println(result);

    }
}