找出字符串中出现次数最多的字符和其出现的数量

public static void main(String [] params){
        //查询一个字符串中出现在最多的字符
        String str = "aacssdefeffffettgggeewwwwwggggrhhh"; 
        String maxChar = "";    //出现次数最多的字符
        int maxCount = 0;       //出现的次数

        Map<Character , Integer> charMap = new HashMap<>();
        for (int i = 0; i < str.length(); i++) {
            //当前字符
            Character currChar = str.charAt(i);
            if(!charMap.containsKey(currChar)){ //不重复的字符作为key
                charMap.put(currChar,0 );
            }
        }

        //计算每个字符出现的数量
        for (int i = 0; i < str.length(); i++) {
            //当前字符
            Character currChar = str.charAt(i);
            for (Character key : charMap.keySet()) {
                if(key.equals(currChar)){
                    Integer val = charMap.get(key);
                    val++;
                    charMap.put(key, val);
                    if(val>maxCount){
                        maxCount = val;
                        maxChar =String.valueOf(currChar);
                    }
                }
            }
        }

        //循环输出每个字符出现的数量
        for (Character key : charMap.keySet()) {
            System.out.println(key+"出现的数量为："+charMap.get(key));
        }
        System.out.println("出现次数最多的是"+maxChar+"，总出现"+maxCount+"次");

    }