DAY_OF_WEEK总是在Java GregorianCalendar中返回7

Question

所以我想用Java GregorianCalendar做一些似乎比它应该更难的事情.我希望从月份和日期获得一周中的某一天.但它不会那样做.我知道人们经常会得到错误的答案,因为他们不知道月份是从0编号而DAY_OF_WEEK从1编号(就像这里和这里一样).但那不是我的问题.我的问题是,无论我将日期设置为什么,DAY_OF_WEEK总是会返回7.当我将GregorianCalendar转换为字符串时,DAY_OF_WEEK显示为？,即使我已设置年,月和dayOfMonth.

发生这种情况的代码:

GregorianCalendar theDate;

public ObservableDate(int year, int month, int dayOfMonth, int hourOfDay, int minute, int second)
{
    theDate = new GregorianCalendar(year, month, dayOfMonth, hourOfDay, minute, second);
    theDate.setFirstDayOfWeek(GregorianCalendar.SUNDAY);
    System.out.println("DAY_OF_WEEK = "+theDate.DAY_OF_WEEK);
    System.out.println(theDate.toString());
}

调用它的代码:

    ObservableDate theDate = new ObservableDate(2001, 3, 24, 9, 00, 00);

输出:

DAY_OF_WEEK = 7
java.util.GregorianCalendar[time=?,areFieldsSet=false,areAllFieldsSet=false,lenient=true,zone=sun.util.calendar.ZoneInfo[id="America/New_York",offset=-18000000,dstSavings=3600000,useDaylight=true,transitions=235,lastRule=java.util.SimpleTimeZone[id=America/New_York,offset=-18000000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,endTimeMode=0]],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=?,YEAR=2001,MONTH=3,WEEK_OF_YEAR=?,WEEK_OF_MONTH=?,DAY_OF_MONTH=24,DAY_OF_YEAR=?,DAY_OF_WEEK=?,DAY_OF_WEEK_IN_MONTH=?,AM_PM=0,HOUR=9,HOUR_OF_DAY=9,MINUTE=0,SECOND=0,MILLISECOND=?,ZONE_OFFSET=?,DST_OFFSET=?]

知道为什么会这样吗？

Answer 1

您正在访问字段常量而不是获取其值.我相信你想用的东西,

System.out.println("DAY_OF_WEEK = " + theDate.get(Calendar.DAY_OF_WEEK));