更改流

Question

我很想知道如何改变：

 for (UserIndex.CoachingArea coachingArea : userIndex.coachingAreas){
            for (UserIndex.CoachingWeekRef coachingWeekRef : coachingArea.weeks){
                if (coachingWeekRef.trackingDays != null){
                    for (UserIndex.TrackingDay trackingDay : coachingWeekRef.trackingDays)
                        if (!trackingDay.status.equals(TrackingStatusEnum.WAITING.toString())) {
                            trackingDataStore.saveFirstCheck(false);
                        }
                }
            }
        }

正在进行中。 这就是我得到的：

 Stream.of(userIndex.coachingAreas)
                .forEach(coachingArea -> Stream.of(coachingArea.weeks)
                        .filter(coachingWeekRef -> coachingWeekRef.trackingDays != null)
                        .forEach(coachingWeekRef -> Stream.of(coachingWeekRef.trackingDays)
                        .filter(trackingDay -> !trackingDay.status.equals(TrackingStatusEnum.WAITING.toString()))
                        )
                );

如何调用最后一种方法来保存数据？

Answer 1

只需添加另一个forEach。但是这一次，使lambda成为一个陈述，而不是一个表达式（在它周围加上括号）。

final TrackingDataStore tds = trackingDataStore; // or whatever type it is
final String WAITING = TrackingStatusEnum.WAITING.toString();
Stream.of(userIndex.coachingAreas)
      .forEach(coachingArea -> Stream.of(coachingArea.weeks)
              .filter(coachingWeekRef -> coachingWeekRef.trackingDays != null)
              .forEach(coachingWeekRef -> Stream.of(coachingWeekRef.trackingDays)
                      .filter(trackingDay -> !trackingDay.status.equals(WAITING))
                      .forEach(trackingDay -> { tds.saveFirstCheck(false); }) // <-- here
                      )
              );

Answer 2

您可以使用flatMap：

来完成此操作

Stream.of(userIndex.coachingAreas)
 .flatMap(coachingArea -> Stream.of(coachingArea.weeks))
 .filter(coachingWeekRef -> coachingWeekRef.trackingDays != null)
 .flatMap(coachingWeekRef -> Stream.of(coachingWeekRef.trackingDays))
 .filter(trackingDay -> !trackingDay.status.equals(TrackingStatusEnum.WAITING.toString()))
 .forEach(trackingDay -> trackingDataStore.saveFirstCheck(false));

这假定您要为trackingDay调用多个trackingDataStore.saveFirstCheck(false)。

如果您只想拨打trackingDataStore.saveFirstCheck(false)一次（如果所有过滤器都已通过），您可以使用findAny：

Stream.of(userIndex.coachingAreas)
 .flatMap(coachingArea -> Stream.of(coachingArea.weeks))
 .filter(coachingWeekRef -> coachingWeekRef.trackingDays != null)
 .flatMap(coachingWeekRef -> Stream.of(coachingWeekRef.trackingDays))
 .filter(trackingDay -> !trackingDay.status.equals(TrackingStatusEnum.WAITING.toString()))
 .findAny()
 .ifPresent(trackingDay -> trackingDataStore.saveFirstCheck(false));