java类的组成元素_jdk8 取集合中对象元素组成新的集合
Listmembers=newtermTeamMemberDao.queryTeamMember(teamNo);ListuserIds=members.stream().map(m->m.getTeacherId()).collect(Collectors.toList());JDK引入了Optional，有时候代码有点难理解，如:Optional.ofNullable(service.m...
