java8 新特性 stream 操作

文章中方法适用于 Java 1.8 及以上版本

//按年龄排序
List collect = list.stream()
    .sorted((e1, e2) -> {
        //先按年龄排序
        return e1.getAge().compareTo(e2.getAge());
    })
    .collect(Collectors.toList());

List collect = list.stream()
   //选出年龄大于35岁的
   .filter((e) -> e.getAge() > 35)
   //只要前2个
   .limit(2)
   .collect(Collectors.toList());

List hospitalDepartmentList = hospitalWardVos.stream()
	.collect(Collectors.collectingAndThen(
		 Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(
				HospitalWardVo::getWardAttributesId))), ArrayList::new)
        );

  List departmentClasss = result.stream().collect(
  		Collectors.collectingAndThen(
                Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(
                   o -> o.getHospitalId() + ";" + o.getStandardDepartmentClassId()
                ))), ArrayList::new));

List wardIds = userWardDepartments.stream().map(
	UserWardDepartment::getId).collect(Collectors.toList()
);

List