关于时间的util类，以后方便查阅

public static int lastDayOfMonth(int year, int month)
  {
    if (month == 2)
    {
      if (isLeapYear(year)) {
        return 29;
      }
      return 28;
    }
    if ((month == 1) || (month == 3) || (month == 5) || (month == 7) || (month == 8) || (month == 10) ||
      (month == 12)) {
      return 31;
    }
    return 30;
  }
 
  public static boolean isLeapYear(int year)
  {
    if ((year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0))) {
      return true;
    }
    return false;
  }
 
  public static Date dateInstance(int year, int month, int day)
  {
    Calendar c = Calendar.getInstance();
    c.set(year, month - 1, day, 0, 0, 0);
    return c.getTime();
  }
 
  public static Date dateInstance(int year, int month, int day, int hour, int min, int sec)
  {
    Calendar c = Calendar.getInstance();
    c.set(year, month - 1, day, hour, min, sec);
    return c.getTime();
  }
 
  public static Calendar calendarInstance(Date d)
  {
    Calendar c = Calendar.getInstance();
    c.setTime(d);
    return c;
  }
 
  public static int weekDay(Date d)
  {
    Calendar c = Calendar.getInstance();
    c.setTime(d);
    return c.get(7);
  }
 
  public static int weekCountOfMonth(int year, int month)
  {
    int lastDay = lastDayOfMonth(year, month);
    Calendar c = Calendar.getInstance();
    c.set(year, month - 1, lastDay);
    return c.get(4);
  }
 
  public static int firstDayOfWeekDay(int year, int month, int argWeekDay)
  {
    Date d = dateInstance(year, month, 1);
    int weekday = weekDay(d);
    if (weekday == argWeekDay) {
      return 1;
    }
    if (weekday > argWeekDay) {
      return 1 + (7 - (weekday - argWeekDay));
    }
    return 1 + (argWeekDay - weekday);
  }
 
  public static int lastDayOfWeekDay(int year, int month, int argWeekDay)
  {
    int lastDay = lastDayOfMonth(year, month);
    int weekday = weekDay(dateInstance(year, month, lastDay));
    if (weekday == argWeekDay) {
      return lastDay;
    }
    if (weekday < argWeekDay) {
      return lastDay - (7 - (argWeekDay - weekday));
    }
    return lastDay - (weekday - argWeekDay);
  }
 
  public static int[] lastMonth(Date d)
  {
    Calendar c = Calendar.getInstance();
    c.setTime(d);
    int year = c.get(1);
    int month = c.get(2) + 1;
    if (month == 1) {
      return new int[] { year - 1, 12 };
    }
    return new int[] { year, month - 1 };
  }
 
  public static int[] lastMonth(int year, int month)
  {
    return lastMonth(dateInstance(year, month, 1));
  }
 
  public static int[] nextMonth(Date d)
  {
    Calendar c = Calendar.getInstance();
    c.setTime(d);
    int year = c.get(1);
    int month = c.get(2) + 1;
    if (month == 12) {
      return new int[] { year + 1, 1 };
    }
    return new int[] { year, month + 1 };
  }
 
  public static int[] nextMonth(int year, int month)
  {
    return nextMonth(dateInstance(year, month, 1));
  }
 
  public static long daysBetween(Date startDate, Date endDate)
  {
    return (endDate.getTime() - startDate.getTime()) / ONE_DAY_MILLIS;
  }
 
  public static Date addDays(Date d, int days)
  {
    if (d == null) {
      return null;
    }
    return new Date(d.getTime() + days * ONE_DAY_MILLIS);
  }
 
  public static Date addMonths(Date d, int months)
  {
    if (months == 0) {
      return d;
    }
    Calendar c = calendarInstance(d);
    int day = c.get(5);
    int hour = c.get(11);
    int min = c.get(12);
    int sec = c.get(13);
   
    Date mydate = d;
    if (months > 0) {
      for (int kk = 0; kk < months; kk++)
      {
        int[] tmp = nextMonth(mydate);
        mydate = dateInstance(tmp[0], tmp[1], 1);
      }
    } else {
      for (int kk = 0; kk > months; kk--)
      {
        int[] tmp = lastMonth(mydate);
        mydate = dateInstance(tmp[0], tmp[1], 1);
      }
    }
    c = calendarInstance(mydate);
    int year = c.get(1);
    int month = c.get(2) + 1;
    int lastDay = lastDayOfMonth(year, month);
    if (day > lastDay) {
      day = lastDay;
    }
    return dateInstance(year, month, day, hour, min, sec);
  }
 
  public static String toString(Date d, String format)
  {
    return new SimpleDateFormat(format).format(d);
  }
 
  public static Date toDate(String dateString, String format)
  {
    try
    {
      return new SimpleDateFormat(format).parse(dateString);
    }
    catch (ParseException e)
    {
      throw new RuntimeException(e);
    }
  }
 
  public static String getStrYear()
  {
    return new SimpleDateFormat("yyyy").format(new Date());
  }
 
  public static String getStrMonth()
  {
    return new SimpleDateFormat("MM").format(new Date());
  }
 
  public static String getStrDay()
  {
    return new SimpleDateFormat("dd").format(new Date());
  }
 
  public static String getStrYearMonthDay()
  {
    return new SimpleDateFormat("yyyyMMdd").format(new Date());
  }
 
  public static Date getCurDate()
  {
    return new Date();
  }
 
  public static BigDecimal calDays(Date beginDate, Date endDate)
  {
    if ((beginDate != null) && (endDate != null))
    {
      BigDecimal days = new BigDecimal(daysBetween(beginDate, endDate));
      return days.setScale(6, 4);
    }
    return null;
  }
 
  public static Date truncDate(Date d, String format)
  {
    Calendar c = calendarInstance(d);
    int year = c.get(1);
    int mon = c.get(2) + 1;
    int day = c.get(5);
    int hour = c.get(11);
    int min = c.get(12);
    int sec = c.get(13);
    if (format.equals("yyyy")) {
      return dateInstance(year, 1, 1);
    }
    if (format.equals("MM")) {
      return dateInstance(year, mon, 1);
    }
    if (format.equals("dd")) {
      return dateInstance(year, mon, day);
    }
    if (format.equals("HH")) {
      return dateInstance(year, mon, day, hour, 0, 0);
    }
    if (format.equals("mm")) {
      return dateInstance(year, mon, day, hour, min, 0);
    }
    if (format.equals("ss")) {
      return dateInstance(year, mon, day, hour, min, sec);
    }
    return d;
  }
 
  public static Date padToMax(Date d, String format)
  {
    Calendar c = calendarInstance(d);
    int year = c.get(1);
    int mon = c.get(2) + 1;
    int day = c.get(5);
    int hour = c.get(11);
    int min = c.get(12);
    int sec = c.get(13);
    if (format.equals("yyyy")) {
      return dateInstance(year, 12, 31, 23, 59, 59);
    }
    if (format.equals("MM")) {
      return dateInstance(year, mon, lastDayOfMonth(year, mon), 23, 59, 59);
    }
    if (format.equals("dd")) {
      return dateInstance(year, mon, day, 23, 59, 59);
    }
    if (format.equals("HH")) {
      return dateInstance(year, mon, day, hour, 59, 59);
    }
    if (format.equals("mm")) {
      return dateInstance(year, mon, day, hour, min, 59);
    }
    if (format.equals("ss")) {
      return dateInstance(year, mon, day, hour, min, sec);
    }
    return d;
  }
 
  public static Timestamp date2Timestamp(Date d)
  {
    Calendar sysCal = Calendar.getInstance();
    sysCal.setTime(d);
    return new Timestamp(sysCal.getTimeInMillis());
  }
 
  public static String timestamp2String(Timestamp t)
  {
    String n = t.toString();
    int vv = n.indexOf(".");
    String bb = n.substring(0, vv);
    return bb;
  }
 
  public static Date strToDate(String str, String dateformat)
    throws ParseException
  {
    DateFormat format = new SimpleDateFormat(dateformat);
    Date date = format.parse(str);
    return date;
  }
 
  public static String getCurrentSysTimeNow()
  {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    Date date = new Date();
    return sdf.format(date);
  }
 
  public static String getCurrentSysTimeNow(String s)
  {
    Date date = new Date();
    s = s.length() < 4 ? "yyyy-MM-dd HH:mm:ss" : s;
    SimpleDateFormat sdf = new SimpleDateFormat(s);
    return sdf.format(date);
  }
 
  /**
  * 得到当前月份
  * @return
  */
 public static String getCurrentMonthInfo(){
  java.util.Calendar calendar = java.util.Calendar.getInstance();
  int monthI = calendar.get(Calendar.MONTH) + 1;
  return monthI + "";
 }
 /**
  * 得到当前年份
  * @return
  */
 public static String getCurrentYearInfo(){
  java.util.Calendar calendar = java.util.Calendar.getInstance();
  int year = calendar.get(Calendar.YEAR) ;
  return year + "";
 }