给定一个字符串，打印输出有重复的字符和重复的次数，并且按照重复的次数升序输出

public class StringDemo {
    public static void main(String[] args) {
        String str = "asdzxasdqweasdzs";
        char[] chars = str.toCharArray();
        Map<Character, Integer> map = new HashMap<>();
        for (char ch : chars) {
            if (map.containsKey(ch)) {
                map.put(ch, map.get(ch) + 1);
            } else {
                map.put(ch, 1);
            }
        }
        System.out.println("map：" + map);
        //排序
        List<Map.Entry<Character, Integer>> list = new ArrayList<>();
        for (Map.Entry<Character, Integer> entry : map.entrySet()) {
            list.add(entry);
        }
        
        Collections.sort(list, new Comparator<Map.Entry<Character, Integer>>() {
            @Override
            public int compare(Map.Entry<Character, Integer> o1, Map.Entry<Character, Integer> o2) {
                return o1.getValue() - o2.getValue();
            }
        });
        System.out.println("排序后：" + list);
    }
}

结果：
map：{a=3, q=1, s=4, d=3, e=1, w=1, x=1, z=2}
排序后：[q=1, e=1, w=1, x=1, z=2, a=3, d=3, s=4]