常用java date方法集合（常用java date方法集合）

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1、常用javadate方法集合（常用javadate方法集合）1.calculatethemaximumnumberofdaysinJanuaryCalendar,time=Calendar.getInstance();Time.clear();Time.set(Calendar.YEAR,year);//yearisintTime.set(Calendar.MONTH,i-1);//note,Calendardefaultis0JanuaryIntday=time.getActualMaximum(Calendar.DAY_OF_MONTH

2、);//numberofdaysthismonth.Note:beforeusingthesetmethod,youmustfirstclear,otherwisemanymessageswillinheritfromthecurrentsystemtimeTransformationof2.CalendarandDate(1)CalendarisconvertedtoDateCalendar,cal=Calendar.getInstance();Date,date=cal.getTime();(2)DateisconvertedtoCal

3、endarDate,date=new,Date();Calendar,cal=Calendar.getInstance();Cal.setTime(date);3.formattheoutputdateandtime(thisisusedmore)Date,date=new,Date();SimpleDateFormatdf=newSimpleDateFormat("yyyy-MM-ddhh:mm:ss");Stringtime=df.format(date);System.out.println(time);4.calculatethef

4、irstfewweeksoftheyear(1)calculatewhatdayaweekisinayearCalendar,cal=Calendar.getInstance();Cal.set(Calendar.YEAR,2006);Cal.set(Calendar.MONTH,8);Cal.set(Calendar.DAY_OF_MONTH,3);Intweekno=cal.get(Calendar.WEEK_OF_YEAR);(2)whatisthefirstweekoftheyear?SimpleDateFormat,df=new,

5、SimpleDateFormat("yyyy-MM-dd");Calendar,cal=Calendar.getInstance();Cal.set(Calendar.YEAR,2006);Cal.set(Calendar.WEEK_OF_YEAR,1);Cal.set(Calendar.DAY_OF_WEEK,Calendar.MONDAY);System.out.println(df.format(cal.getTime()));Output:2006-01-02Theuseof5.add()androll()isnotverycomm

6、on(1)add()methodSimpleDateFormat,df=new,SimpleDateFormat("yyyy-MM-dd");Calendar,cal=Calendar.getInstance();Cal.set(Calendar.YEAR,2006);Cal.set(Calendar.MONTH,8);Cal.set(Calendar.DAY_OF_MONTH,3);Cal.add(Calendar.DATE,-4);Date,date=cal.getTime();System.out.println(df.format(

7、date));Cal.add(Calendar.DATE,4);Date=cal.getTime();System.out.println(df.format(date));Output:2006-08-302006-09-03(2)rollmethodCal.set(Calendar.YEAR,2006);Cal.set(Calendar.MONTH,8);Cal.set(Calendar.DAY_OF_MONTH,3);Cal.roll(Calendar.DATE,-4);Date=cal.getTime();System.out.pr

8、intln(df.format(date));Cal.roll(Calendar.DATE,4);Date=cal.getTime();System.out.println(df