統計一個字符串中出現次數最多的字符

題目：統計給出的字符串中出現次數最多的字符
解題思路：將字符依次映射進哈希表，以字符作爲key，出現次數作爲value，最後比較得出結果
代碼如下：

public void countCharacterInString(){
	String target = "hello world  what about you today";
	//將包含的字符放入哈希表，字符作爲key，出現次數作爲value
	char[] alph = target.toCharArray();
	Map<Character,Integer> aa = new HashMap<Character,Integer>();
	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);
		 }
	}
	//比較獲取出現最多次數的字符
	Set<Character> 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);
}