统计字符串中每个字符出现的次数

输入一串字符串，统计字符串中每个字符出现的次数，例如输入“asdffffssa”,输出a(2)d(1)f(4)s(3)

Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
//        HashMap<Character, Integer> hashMap = new HashMap<Character, Integer>();
        TreeMap<Character, Integer> treeMap = new TreeMap<Character, Integer>();
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (treeMap.containsKey(c)) {
                Integer value = treeMap.get(c);
                treeMap.put(c, value + 1);
            } else {
                treeMap.put(c, 1);
            }
        }
        for (Map.Entry<Character, Integer> m : treeMap.entrySet()) {
            System.out.print(m.getKey() + "(" + m.getValue() + ")");
        }