Java以逗号分隔的String字符串转int集合，list集合转逗号分隔的字符串

字符串转集合

String ids = "7,8,9,10,11";

List idList = Arrays.stream(ids.split(",")).map(Integer::parseInt).collect(Collectors.toList());

集合转字符串（需要引入hutool工具包）

List userIds = users.stream().map(MatchGroupUserEntity::getMallUserId).collect(Collectors.toList());
 ids = Joiner.on(",").join(userIds);