統計字符串每個字符出現的次數

package cn.yschung.demo;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Set;

public class StirngDemo {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String ch = "aababcabcdabcddasae";
        // 轉成數組
        char[] arr = ch.toCharArray();
        HashMap<Character, Integer> hm = new HashMap<Character, Integer>();

        for (char s : arr) {
            // 得到鍵值
            Integer c = hm.get(s);
            if (c == null) {// 如果c=空,則集合的值就為1
                hm.put(s, 1);
            } else {
                c++;
                hm.put(s, c);
            }
        }

        Set<Character> set = hm.keySet();
        // 遍歷集合
        for (Character i : set) {
            Integer ss = hm.get(i);// 獲取value值
            StringBuilder sb = new StringBuilder();// 創建StringBuilder
            sb.append(i).append("(").append(ss).append(")");
            String result = sb.toString();
            System.out.println(result);
        }

    }

}