Java8 .stream().map(Bean::getId).collect(Collectors.toList())

从数据库中某个对象集合，如日志，提取出日志的id集合，后续使用

List<VisitorLog> searchList = visitorLogMapper.search(param.getAccount(),param.getStatus());
List<String> visitorLogIdList = searchList.stream().map(VisitorLog::getId).collect(Collectors.toList());

等同于：

List<VisitorLog> searchList= visitorLogMapper.search(param.getAccount(),param.getStatus());
for (VisitorLog visitorLog : searchList) {
            String id = visitorLog.getId();
            visitorLogIdList.add(id);
        }