stream灵活应用，list和String互转

1. 获取list对象中的指定字段
   List userId= scheduleStudents.stream().map(User::getUserId).collect(Collectors.toList());      List ids = list.stream().map(u-> u.getUserId()).collect(Collectors.toList());

2. string转list

   List idList = Arrays.asList(componentRelate.getIds().split(","));

3. string转list

   List idList = Arrays.asList(componentRelate.getIds().split(","))
           .stream().map(s -> Long.parseLong(s.trim())).collect(Collectors.toList());

4. 对象互转
   List finishCourse = finishCourseSchedules.stream().map(a->{ return getScheduleBase(a); }).collect(Collectors.toList());