统计字符串中每个字母出现的次数

package com.ibeifeng;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Set;

/*3 "acfabfaefcbefcaefbcecdfabccdec",获取字符串中每一个字母出现的次数。
 * 如：结果:a(5)b(4)c(8)d(2)e(4)f(6)    (15分)*/
public class Demo3 {
    public static void main(String[] args) {
        String str = "acfabfaefcbefcaefbcecdfabccdec";
        HashMap<Character,Integer> hm = new HashMap();
        //存入
        for(int i=0; i<str.length(); i++) {
            char ch = str.charAt(i);
            if(hm.containsKey(ch)) {
                int count = hm.get(ch); 
                hm.put(ch, count+1);
            } else {
                hm.put(ch, 1);
            }
        }
        //遍历
//      Set<Character> set = hm.keySet();
//      String result = "";
//      for (Character key : set) {
//          result=result+key+"("+hm.get(key)+")";
//      }
//      System.out.println(result);
        //遍历
        Set<Character> set = hm.keySet();
        String result = "";
        ArrayList<Character> arrList= new ArrayList();
        arrList.addAll(set);
        Collections.sort(arrList);
        for (Character key : arrList) {
            result=result+key+"("+hm.get(key)+")";
        }
        System.out.println(result);
    }
}