输入一串字符串，统计各个字符出现的次数

public class StatisticZEN {
    public static void main(String[] args) {
        String str = "中国aadf的111萨bbb菲的zz萨菲";
        showFrequency(str);

    private static HashMap<Character, Integer> showFrequency(String str) {
        HashMap<Character, Integer> map = new HashMap<Character, Integer>();
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            Integer num = map.get(c);
            if(num == null)
                num = 1;
            else
                num ++;
            map.put(c,num);
        }
        return map;
    }
}