public class FindChar{
    public static void main(String[] args){
        findChar("什麽是什麽意義咦咦咦咦");
    }
 
    public static void findChar(String msg){
        if(null == msg)
            return;
        Map<String,String> charMap = new HashMap<String,String>();
        int base = 0;
        String maxChar = "";
        for(int i=0; i < msg.length(); i++){
            String word = String.valueOf(msg.charAt(i));
            if(!charMap.containsKey(word)){
                charMap.put(word, "1");
            }else{
                int index = Integer.valueOf(charMap.get(word)) + 1;
                charMap.put(word, String.valueOf(index));
                if(index > base){
                    base = index;
                    maxChar = word;
                }
            }
        }
        // 出現最多次數
        System.out.println(base);
        // 出現做多次數字符
        System.out.println(maxChar);
    }
}

　　忘記在網上哪裏看到過的。不是原創--特此聲明

字符串查找重復字符最多的