统计字符串每个字符出现的次数

 1 package cn.yschung.demo;
 2 
 3 import java.util.Arrays;
 4 import java.util.HashMap;
 5 import java.util.Set;
 6 
 7 public class StirngDemo {
 8 
 9     public static void main(String[] args) {
10         // TODO Auto-generated method stub
11         String ch = "aababcabcdabcddasae";
12         // 转成数组
13         char[] arr = ch.toCharArray();
14         HashMap<Character, Integer> hm = new HashMap<Character, Integer>();
15 
16         for (char s : arr) {
17             // 得到键值
18             Integer c = hm.get(s);
19             if (c == null) {// 如果c=空,则集合的值就为1
20                 hm.put(s, 1);
21             } else {
22                 c++;
23                 hm.put(s, c);
24             }
25         }
26 
27         Set<Character> set = hm.keySet();
28         // 遍历集合
29         for (Character i : set) {
30             Integer ss = hm.get(i);// 获取value值
31             StringBuilder sb = new StringBuilder();// 创建StringBuilder
32             sb.append(i).append("(").append(ss).append(")");
33             String result = sb.toString();
34             System.out.println(result);
35         }
36 
37     }
38 
39 }