Question

我在scala中有以下代码：

import java.util.Calendar
var calendar = Calendar.getInstance();
var lastTimeProcessed = calendar.set(Calendar.HOUR_OF_DAY, 0)

在spark-shell中，创建lastTimeProcessed之后，看起来这个变量是Unit，但我想要的是初始化为00:00。

这是控制台结果：

lastTimeProcessed: Unit = ()

我做错了什么？

Answer 1

set会改变实例的状态并返回Unit作为输出类型。

calendar的状态已更改。现在打印calendar以查看新的变异状态。

calendar.getTime

设置HOUR_OF_DAY

后会显示时间

 scala> calendar.get(Calendar.HOUR_OF_DAY)
 res12: Int = 0

Answer 2

日历集返回无效但它确实会根据此次运行更改HOUR_OF_DAY或MINUTE的值：

scala> import java.util.Calendar
import java.util.Calendar

scala> var calendar = Calendar.getInstance();
calendar: java.util.Calendar = java.util.GregorianCalendar[time=1474194792722,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Manila",offset=28800000,dstSavings=0,useDaylight=false,transitions=10,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2016,MONTH=8,WEEK_OF_YEAR=39,WEEK_OF_MONTH=4,DAY_OF_MONTH=18,DAY_OF_YEAR=262,DAY_OF_WEEK=1,DAY_OF_WEEK_IN_MONTH=3,AM_PM=1,HOUR=6,HOUR_OF_DAY=18,MINUTE=33,SECOND=12,MILLISECOND=722,ZONE_OFFSET=28800000,DST_OFFSET=0]

scala> var lastTimeProcessed = calendar.set(Calendar.HOUR_OF_DAY, 0)
lastTimeProcessed: Unit = ()

scala> calendar
res0: java.util.Calendar = java.util.GregorianCalendar[time=?,areFieldsSet=false,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Manila",offset=28800000,dstSavings=0,useDaylight=false,transitions=10,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2016,MONTH=8,WEEK_OF_YEAR=39,WEEK_OF_MONTH=4,DAY_OF_MONTH=18,DAY_OF_YEAR=262,DAY_OF_WEEK=1,DAY_OF_WEEK_IN_MONTH=3,AM_PM=1,HOUR=6,HOUR_OF_DAY=0,MINUTE=33,SECOND=12,MILLISECOND=722,ZONE_OFFSET=28800000,DST_OFFSET=0]

scala> calendar.set(Calendar.MINUTE, 0)

scala> calendar
res2: java.util.Calendar = java.util.GregorianCalendar[time=?,areFieldsSet=false,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Manila",offset=28800000,dstSavings=0,useDaylight=false,transitions=10,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2016,MONTH=8,WEEK_OF_YEAR=39,WEEK_OF_MONTH=4,DAY_OF_MONTH=18,DAY_OF_YEAR=262,DAY_OF_WEEK=1,DAY_OF_WEEK_IN_MONTH=3,AM_PM=1,HOUR=6,HOUR_OF_DAY=0,MINUTE=0,SECOND=12,MILLISECOND=722,ZONE_OFFSET=28800000,DST_OFFSET=0]

未经请求的建议，请使用joda时间库。

如何在scala中设置Calendar的小时

2 个答案: