Map中获得Map的key值

Map中取得Map的key值

//将返回的Map的key 拼成空格隔开的字符串private static String map2String(List<Map> arr){String str = "";for (Map<String, Integer>  m : arr) {Set<String> s = m.keySet();for (String string : s) {str += string + " ";}}return str;}