計算字符串中各字符的個數

方法一：
public class test21 {
    public static void main(String[] args) {
        a("abnclnacnacipnsakkcnsa");
    }

    public static void a(String a){
        while (a.length()!=0){
            int count=a.length();
            char a0=a.charAt(0);
            String[] bs = a.split(String.valueOf(a.charAt(0)));
            if (bs.length!=0){//防止數組越界
            a=bs[0];
            for (int i = 1; i < bs.length; i++) {
                a=a.concat(bs[i]);
            }
            System.out.println(a0+"的個數為"+(count-a.length()));}

            else {
                System.out.println(a.charAt(0)+"的個數為"+a.length());
                break;
            }

        }

    }
方法二：利用map中key不能重復的機制

import java.util.*;

public class Test02 {
    public static void main(String[] args) {
        Scanner s=new Scanner(System.in);
        String a=s.next();
        HashMap<Character,Integer> map = new HashMap();
        for (char c : a.toCharArray()) {
            if (map.containsKey(c)){
                int value =  map.get(c);
                value++;
                map.put(c,value);
            }else
                map.put(c,1);
        }

        Set<Character> set = map.keySet();
        for (Character character : set) {
            System.out.println(character+" "+map.get(character));
        }
    }
}