统计一个字符串中出现次数最多的字符

public void countCharacterInString(){
    String target = "hello world  what about you today";
    //将包含的字符放入哈希表，字符作为key，出现次数作为value
    char[] alph = target.toCharArray();
    Map aa = new HashMap();
    for(Character c:alph){
        if(Character.isWhitespace(c)) continue;
        if(aa.containsKey(c) == false){
             aa.put(c, 1);
         }else{
             aa.put(c, aa.get(c)+1);
         }
    }
    //比较获取出现最多次数的字符
    Set set = aa.keySet();
    Iterator iter = set.iterator();
    Integer count=0;
    Character key = new Character(' ');

    while(iter.hasNext()){
        Character ccc = (Character)iter.next();
        System.out.println(ccc +": "+ aa.get(ccc));
        if(aa.get(ccc) > count){
            count = aa.get(ccc);
            key = ccc;
        }
    }

    System.out.println(key.toString()+" "+ count);
}