我的POJO如下
class EventUser {
private id;
private userId;
private eventId;
}
我按以下方式检索EventUser对象:
List<EventUser> eventUsers = eventUserRepository.findByUserId(userId);
说“eventUsers”如下:
[
{"id":"id200","userId":"001","eventId":"1010"},
{"id":"id101","userId":"001","eventId":"4212"},
{"id":"id402","userId":"001","eventId":"1221"},
{"id":"id301","userId":"001","eventId":"2423"},
{"id":"id701","userId":"001","eventId":"5423"},
{"id":"id601","userId":"001","eventId":"7423"}
]
使用流传输,并且不使用任何中间变量,如何在给定EventUser.id之后过滤和收集事件:
例如:
List<EventUser> filteredByOffSet = eventUsers.stream.SOMEFILTER_AND_COLLECT("id301");
结果应该是:
[{"id":"id301","userId":"001","eventId":"2423"},
{"id":"id701","userId":"001","eventId":"5423"},
{"id":"id601","userId":"001","eventId":"7423"}]
最佳答案
在Java 8中,您需要有状态过滤器
public static <T> Predicate<T> from(Predicate<T> test) {
boolean[] found = { false };
// once found, always true
return t -> found[0] || (found[0] = test.test(t));
}
注意:这仅对单线程流有意义。
List<EventUser> filteredByOffSet =
eventUsers.stream()
.filter(from(e -> "id301".equals(e.getId()))
.collect(Collectors.toList());