本月的开始日期和结束日期

Question

我需要Java中当前月份的开始日期和结束日期。当JSP页面使用当前月份加载时，它应该自动计算该月份的开始日期和结束日期。它应该与年月无关。这是一个月有31天或30天或28天。这也应该满足闰年。你能帮我解决吗？

例如，如果我在一个列表框中我需要开始日期是1和结束日期为31

Answer 1

有选择的五月，你去：

public Pair<Date, Date> getDateRange() { 
    Date begining, end; 

    { 
     Calendar calendar = getCalendarForNow(); 
     calendar.set(Calendar.DAY_OF_MONTH, 
       calendar.getActualMinimum(Calendar.DAY_OF_MONTH)); 
     setTimeToBeginningOfDay(calendar); 
     begining = calendar.getTime(); 
    } 

    { 
     Calendar calendar = getCalendarForNow(); 
     calendar.set(Calendar.DAY_OF_MONTH, 
       calendar.getActualMaximum(Calendar.DAY_OF_MONTH)); 
     setTimeToEndofDay(calendar); 
     end = calendar.getTime(); 
    } 

    return Pair.of(begining, end); 
} 

private static Calendar getCalendarForNow() { 
    Calendar calendar = GregorianCalendar.getInstance(); 
    calendar.setTime(new Date()); 
    return calendar; 
} 

private static void setTimeToBeginningOfDay(Calendar calendar) { 
    calendar.set(Calendar.HOUR_OF_DAY, 0); 
    calendar.set(Calendar.MINUTE, 0); 
    calendar.set(Calendar.SECOND, 0); 
    calendar.set(Calendar.MILLISECOND, 0); 
} 

private static void setTimeToEndofDay(Calendar calendar) { 
    calendar.set(Calendar.HOUR_OF_DAY, 23); 
    calendar.set(Calendar.MINUTE, 59); 
    calendar.set(Calendar.SECOND, 59); 
    calendar.set(Calendar.MILLISECOND, 999); 
} 

PS：Pair类是根本一对两个值。

Answer 2

如果您有选择，您最好避免使用可怕的Java Date API，并改用Jodatime。这里有一个例子：

LocalDate monthBegin = new LocalDate().withDayOfMonth(1); 
LocalDate monthEnd = new LocalDate().plusMonths(1).withDayOfMonth(1).minusDays(1); 

Answer 3

随着date4j库：

dt.getStartOfMonth(); 
dt.getEndOfMonth(); 

Answer 4

Date begining, ending; 
Calendar calendar_start =BusinessUnitUtility.getCalendarForNow(); 
    calendar_start.set(Calendar.DAY_OF_MONTH,calendar_start.getActualMinimum(Calendar.DAY_OF_MONTH)); 
    begining = calendar_start.getTime(); 
    String start= DateDifference.dateToString(begining,"dd-MMM-yyyy");//sdf.format(begining); 


    //   for End Date of month 
    Calendar calendar_end = BusinessUnitUtility.getCalendarForNow(); 
    calendar_end.set(Calendar.DAY_OF_MONTH,calendar_end.getActualMaximum(Calendar.DAY_OF_MONTH)); 
     ending = calendar_end.getTime(); 
     String end=DateDifference.dateToString(ending,"dd-MMM-yyyy");//or sdf.format(end); 

enter code here 



public static Calendar getCalendarForNow() { 
     Calendar calendar = GregorianCalendar.getInstance(); 
     calendar.setTime(new Date()); 
     return calendar; 
    } 

Answer 5

使之更模块化，你可以有计算的startDate或结束日期一个主要功能，比你可以有个人的方法到getMonthStartDate，getMonthEndDate和getMonthStartEndDate。根据您的要求使用方法。

public static String getMonthStartEndDate(){ 
    String start = getMonthDate("START"); 
    String end = getMonthDate("END"); 
    String result = start + " to " + end; 
    return result; 
} 

public static String getMonthStartDate(){ 
    String start = getMonthDate("START"); 
    return start; 
} 

public static String getMonthEndDate(){ 
    String end = getMonthDate("END"); 
    return end; 
} 

/** 
* @param filter 
* START for start date of month e.g. Nov 01, 2013 
* END for end date of month e.g. Nov 30, 2013 
* @return 
*/ 
public static String getMonthDate(String filter){ 
      String MMM_DD_COMMA_YYYY  = "MMM dd, yyyy"; 
    SimpleDateFormat sdf = new SimpleDateFormat(MMM_DD_COMMA_YYYY); 
    sdf.setTimeZone(TimeZone.getTimeZone("PST")); 
    sdf.format(GregorianCalendar.getInstance().getTime()); 

    Calendar cal = GregorianCalendar.getInstance(); 
    int date = cal.getActualMinimum(Calendar.DATE); 
    if("END".equalsIgnoreCase(filter)){ 
     date = cal.getActualMaximum(Calendar.DATE); 
    } 
    cal.set(Calendar.DATE, date); 
    String result = sdf.format(cal.getTime()); 
    System.out.println(" " + result ); 

    return result; 
} 

Answer 6

对于Java 8+，下面方法给当月第一&最后日期为实例LOCALDATE。

public static LocalDate getCurrentMonthFirstDate() { 
    return LocalDate.ofEpochDay(System.currentTimeMillis()/(24 * 60 * 60 * 1000)).withDayOfMonth(1); 
} 

public static LocalDate getCurrentMonthLastDate() { 
    return LocalDate.ofEpochDay(System.currentTimeMillis()/(24 * 60 * 60 * 1000)).plusMonths(1).withDayOfMonth(1).minusDays(1); 
} 

边注：使用的LocalDate.ofEpochDay(...)代替LocalDate.now()给人大大提高性能。此外，使用毫秒每日表达式而不是结束值（即86400000）表现更好。我最初以为后者将执行比表达更好：P

Answer 7

试试这个代码

Calendar calendar = Calendar.getInstance(); 
int yearpart = 2010; 
int monthPart = 11; 
int dateDay = 1; 
calendar.set(yearpart, monthPart, dateDay); 
int numOfDaysInMonth = calendar.getActualMaximum(Calendar.DAY_OF_MONTH); 
System.out.println("Number of Days: " + numOfDaysInMonth); 
System.out.println("First Day of month: " + calendar.getTime()); 
calendar.add(Calendar.DAY_OF_MONTH, numOfDaysInMonth-1); 
System.out.println("Last Day of month: " + calendar.getTime()); 

希望它能帮助。从Java 8

Answer 8

Calendar c = Calendar.getInstance(); 
    int year = c.get(Calendar.YEAR); 
    int month = c.get(Calendar.MONTH); 
    int day = 1; 
    c.set(year, month, day); 
    int numOfDaysInMonth = c.getActualMaximum(Calendar.DAY_OF_MONTH); 
    System.out.println("First Day of month: " + c.getTime()); 
    c.add(Calendar.DAY_OF_MONTH, numOfDaysInMonth-1); 
    System.out.println("Last Day of month: " + c.getTime()); 

Answer 9

尝试LOCALDATE的：

LocalDate today = LocalDate.now(); 
System.out.println("First day: " + today.withDayOfMonth(1)); 
System.out.println("Last day: " + today.withDayOfMonth(today.lengthOfMonth()));