java集合

1.map根据key排序

public static Map<String, String> sortMapByKey(Map<String, String> map) {
        if (map == null || map.isEmpty()) {
            return null;
        }
        Map<String, String> sortMap = new TreeMap<>(new Comparator<String>() {
            @Override
            public int compare(String str1, String str2) {
                return str1.compareTo(str2);
            }
        });
        sortMap.putAll(map);
        return sortMap;
    }