Map<Integer,List<String>> mapBanJI_UserNameList=list.stream().collect(Collectors.groupingBy(UserInfo::getBanJi,Collectors.mapping(UserInfo::getUserName,Collectors.toList())));
Map<Integer,List<String>> mapBanJI_UserNameList=list.stream().collect(Collectors.groupingBy(UserInfo::getBanJi,Collectors.mapping(UserInfo::getUserName,Collectors.toList())));