calendar.clear(Calendar.DATE)不起作用

当然起作用的，你会发现java.util.GregorianCalendar[time=1047605463234,areFieldsSet=true,areAllFieldsSet
=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Shanghai",offset=288
00000,dstSavings=0,useDaylight=false,transitions=19,lastRule=null],firstDayOfWee
k=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2003,MONTH=2,WEEK_OF_YEAR=11,WEEK_OF_MON
TH=3,DAY_OF_MONTH=14,DAY_OF_YEAR=73,DAY_OF_WEEK=6,DAY_OF_WEEK_IN_MONTH=2,AM_PM=0
,HOUR=9,HOUR_OF_DAY=9,MINUTE=31,SECOND=3,MILLISECOND=234,ZONE_OFFSET=28800000,DS
T_OFFSET=0]
java.util.GregorianCalendar[time=?,areFieldsSet=false,areAllFieldsSet=false,leni
                                ^^^ 
ent=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Shanghai",offset=28800000,dstS
avings=0,useDaylight=false,transitions=19,lastRule=null],firstDayOfWeek=1,minima
lDaysInFirstWeek=1,ERA=1,YEAR=2003,MONTH=2,WEEK_OF_YEAR=11,WEEK_OF_MONTH=3,DAY_O
F_MONTH=?,DAY_OF_YEAR=73,DAY_OF_WEEK=6,DAY_OF_WEEK_IN_MONTH=2,AM_PM=0,HOUR=9,HOU
       ^^^ 
R_OF_DAY=9,MINUTE=31,SECOND=3,MILLISECOND=234,ZONE_OFFSET=28800000,DST_OFFSET=0]