Java Date Utils

This java utility is developed for all date related manipulations.It contains 25 methods each one does different functionality.

package testing.com;

import java.util.Date;
import java.text.SimpleDateFormat;
import java.sql.Timestamp;

// Class for the Date Utilities Module.
public class DateUtil
{

 // *****************************************************************
 // *************************** METHODS *****************************
 // *****************************************************************

 // returns a String representing the given day of the week number.
 // will return abbreviated version (3 characters) if shortVersion is
 // true.
 // we assume Sunday = 0; ...; Saturday = 6.
 public String dayOfWeekNumberToString(int dayOfWeekNumber, boolean shortVersion)
 {
  // new day of week string.
  String dayOfWeekString;

  // store the day of week string appropriate to the day of week number.
  switch (dayOfWeekNumber)
  {
   case 0 :
    // depending on whether or not to abbreviate the return, store
    // correct version.
    if (shortVersion)
    {
     // store "Sun" as day of week string.
     dayOfWeekString = "Sun";
    } else
    {
     // store "Sunday" as day of week string.
     dayOfWeekString = "Sunday";
    }

    break;
   case 1 :
    // depending on whether or not to abbreviate the return, store
    // correct version.
    if (shortVersion)
    {
     // store "Mon" as day of week string.
     dayOfWeekString = "Mon";
    } else
    {
     // store "Monday" as day of week string.
     dayOfWeekString = "Monday";
    }

    break;
   case 2 :
    // depending on whether or not to abbreviate the return, store
    // correct version.
    if (shortVersion)
    {
     // store "Tue" as day of week string.
     dayOfWeekString = "Tue";
    } else
    {
     // store "Tuesday" as day of week string.
     dayOfWeekString = "Tuesday";
    }

    break;
   case 3 :
    // depending on whether or not to abbreviate the return, store
    // correct version.
    if (shortVersion)
    {
     // store "Wed" as day of week string.
     dayOfWeekString = "Wed";
    } else
    {
     // store "Wednesday" as day of week string.
     dayOfWeekString = "Wednesday";
    }

    break;
   case 4 :
    // depending on whether or not to abbreviate the return, store
    // correct version.
    if (shortVersion)
    {
     // store "Thu" as day of week string.
     dayOfWeekString = "Thu";
    } else
    {
     // store "Thursday" as day of week string.
     dayOfWeekString = "Thursday";
    }

    break;
   case 5 :
    // depending on whether or not to abbreviate the return, store
    // correct version.
    if (shortVersion)
    {
     // store "Fri" as day of week string.
     dayOfWeekString = "Fri";
    } else
    {
     // store "Friday" as day of week string.
     dayOfWeekString = "Friday";
    }

    break;
   case 6 :
    // depending on whether or not to abbreviate the return, store
    // correct version.
    if (shortVersion)
    {
     // store "Sat" as day of week string.
     dayOfWeekString = "Sat";
    } else
    {
     // store "Saturday" as day of week string.
     dayOfWeekString = "Saturday";
    }

    break;
   default :
    // store an error string.
    dayOfWeekString = "UNKNOWNDAYOFWEEK";

    break;
  }

  // return the day of week string.
  return dayOfWeekString;
 }

 // returns a String representing the given month number.
 // we assume January = 0; ...; December = 11.
 public String monthNumberToString(int monthNumber)
 {
  // new month string.
  String monthString;

  // store the month string appropriate to the month number.
  switch (monthNumber)
  {
   case 0 :
    // store "January" as month string.
    monthString = "January";

    break;
   case 1 :
    // store "February" as month string.
    monthString = "February";

    break;
   case 2 :
    // store "March" as month string.
    monthString = "March";

    break;
   case 3 :
    // store "April" as month string.
    monthString = "April";

    break;
   case 4 :
    // store "May" as month string.
    monthString = "May";

    break;
   case 5 :
    // store "June" as month string.
    monthString = "June";

    break;
   case 6 :
    // store "July" as month string.
    monthString = "July";

    break;
   case 7 :
    // store "August" as month string.
    monthString = "August";

    break;
   case 8 :
    // store "September" as month string.
    monthString = "September";

    break;
   case 9 :
    // store "October" as month string.
    monthString = "October";

    break;
   case 10 :
    // store "November" as month string.
    monthString = "November";

    break;
   case 11 :
    // store "December" as month string.
    monthString = "December";

    break;
   default :
    // store an error string.
    monthString = "UNKNOWNMONTH";

    break;
  }

  // return the month string.
  return monthString;
 }

 // returns the number of days in this month.
 // we assume January = 0; ...; December = 11.
 public int monthNumberToDays(int monthNumber, int currentYear)
 {
  // number of days in the month.
  int dayNumber;

  // store the number of days appropriate to the month number.
  switch (monthNumber)
  {
   case 0 :
    // store 31 as number of days for January.
    dayNumber = 31;

    break;
   case 1 :
    // if it is a leap year, then store 29, otherwise, store 28.
    if (isLeapYear(currentYear))
    {
     // store 29 as number of days for February.
     dayNumber = 29;
    } else
    {
     // store 28 as number of days for February.
     dayNumber = 28;
    }

    break;
   case 2 :
    // store 31 as number of days for March.
    dayNumber = 31;

    break;
   case 3 :
    // store 30 as number of days for April.
    dayNumber = 30;

    break;
   case 4 :
    // store 31 as number of days for May.
    dayNumber = 31;

    break;
   case 5 :
    // store 30 as number of days for June.
    dayNumber = 30;

    break;
   case 6 :
    // store 31 as number of days for July.
    dayNumber = 31;

    break;
   case 7 :
    // store 31 as number of days for August.
    dayNumber = 31;

    break;
   case 8 :
    // store 30 as number of days for September.
    dayNumber = 30;

    break;
   case 9 :
    // store 31 as number of days for October.
    dayNumber = 31;

    break;
   case 10 :
    // store 30 as number of days for November.
    dayNumber = 30;

    break;
   case 11 :
    // store 31 as number of days for December.
    dayNumber = 31;

    break;
   default :
    // store 0 as error.
    dayNumber = 0;

    break;
  }

  // return the number of days in the month.
  return dayNumber;
 }

 // returns whether or not the year is a leap year.
 // slight hack as it compares the first days of the months of 
 // February and March and if they fall on different days of the
 // week, then it is a leap year.
 // yearNumber should be in the following (XX where it is 19XX).
 public boolean isLeapYear(int yearNumber)
 {
  // used to store first day of February.
  Date firstDayOfFebruary;

  // used to store first day of March.
  Date firstDayOfMarch;

  // create/set the first day of February.
  firstDayOfFebruary = new Date(yearNumber, 1, 1, 0, 0, 0);

  // create/set the first day of March.
  firstDayOfMarch = new Date(yearNumber, 2, 1, 0, 0, 0);

  // if the day of the week the first days fall on are different, it
  // is a leap year!
  if (firstDayOfFebruary.getDay() != firstDayOfMarch.getDay())
  {
   // return that it is leap year!
   return true;
  } else
  {
   // return this it is not leap year!
   return false;
  }
 }

 // returns the date by decrementing the given date by one day.
 // if a number if given, then multiple days are decremented.
 public Date decrementByDay(Date date)
 {
  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // if date is already at beginning of valid range, then don't do
  // anything.
  if (!((newDate.getYear() == 70) && (newDate.getMonth() == 0) && (newDate.getDate() == 1)))
  {
   // if we are not at the beginning of the month, then simply go
   // to previous day in the month. otherwise, go to previous month.
   if (newDate.getDate() > 1)
   {
    // simply set to previous day.
    newDate = new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate() - 1, newDate.getHours(), newDate.getMinutes(), newDate.getSeconds());
   } else
   {
    // first go back one month.
    newDate = decrementByMonth(newDate, 1);

    // set date to end of month.
    newDate = new Date(newDate.getYear(), newDate.getMonth(), monthNumberToDays(newDate.getMonth(), newDate.getYear()), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds());
   }
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }
 public Date decrementByDay(Date date, int decrementNum)
 {
  // counter to iteratively decrement.
  int decrementCounter;

  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // iteratively decrement date.
  for (decrementCounter = 1; decrementCounter <= decrementNum; decrementCounter++)
  {
   newDate = decrementByDay(newDate);
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }

 // returns the date by incrementing the given date by one day.
 // if a number if given, then multiple days are incremented.
 public Date incrementByDay(Date date)
 {
  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // if date is already at end of valid range, then don't do
  // anything.
  if (!((newDate.getYear() == 137) && (newDate.getMonth() == 11) && (newDate.getDate() == 31)))
  {
   // if we are not at the end of the month, then simply go
   // to previous day in the month. otherwise, go to previous month.
   if (newDate.getDate() < monthNumberToDays(newDate.getMonth(), newDate.getYear()))
   {
    // simply set to next day.
    newDate = new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate() + 1, newDate.getHours(), newDate.getMinutes(), newDate.getSeconds());
   } else
   {
    // set date to beginning of month.
    newDate = new Date(newDate.getYear(), newDate.getMonth(), 1, newDate.getHours(), newDate.getMinutes(), newDate.getSeconds());

    // first go forward one month.
    newDate = incrementByMonth(newDate, 1);
   }
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }
 public Date incrementByDay(Date date, int incrementNum)
 {
  // counter to iteratively increment.
  int incrementCounter;

  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // iteratively increment date.
  for (incrementCounter = 1; incrementCounter <= incrementNum; incrementCounter++)
  {
   newDate = incrementByDay(newDate);
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }

 // returns the date by decrementing the given date by one week.
 // if a number if given, then multiple weeks are decremented.
 public Date decrementByWeek(Date date)
 {
  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // if date is already at beginning of valid range, then don't do
  // anything.
  if (!((newDate.getYear() == 70) && (newDate.getMonth() == 0) && (newDate.getDate() <= 7)))
  {
   // go 7 days backward.
   newDate = decrementByDay(newDate, 7);
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }
 public Date decrementByWeek(Date date, int decrementNum)
 {
  // counter to iteratively decrement.
  int decrementCounter;

  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // iteratively decrement date.
  for (decrementCounter = 1; decrementCounter <= decrementNum; decrementCounter++)
  {
   newDate = decrementByWeek(newDate);
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }

 // returns the date by incrementing the given date by one week.
 // if a number if given, then multiple weeks are incremented.
 public Date incrementByWeek(Date date)
 {
  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // if date is already at end of valid range, then don't do
  // anything.
  if (!((newDate.getYear() == 137) && (newDate.getMonth() == 11) && (newDate.getDate() > 24)))
  {
   // go 7 days forward.
   newDate = incrementByDay(newDate, 7);
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }
 public Date incrementByWeek(Date date, int incrementNum)
 {
  // counter to iteratively increment.
  int incrementCounter;

  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // iteratively increment date.
  for (incrementCounter = 1; incrementCounter <= incrementNum; incrementCounter++)
  {
   newDate = incrementByWeek(newDate);
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }

 // returns the date by decrementing the given date by one month.
 // if a number if given, then multiple months are decremented.
 public Date decrementByMonth(Date date)
 {
  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // if date is already at beginning of valid range, then don't do
  // anything.
  if (!((newDate.getYear() == 70) && (newDate.getMonth() == 0)))
  {
   // if we are not at the beginning of the current year, then
   // just go to previous month. Otherwise, change years also.
   if (newDate.getMonth() > 0)
   {
    // go to previous month.
    newDate = new Date(newDate.getYear(), newDate.getMonth() - 1, newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds());
   } else
   {
    // go to previous year.
    newDate = decrementByYear(newDate, 1);

    // go to the last month of the previous year.
    newDate = new Date(newDate.getYear(), 11, newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds());
   }
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }
 public Date decrementByMonth(Date date, int decrementNum)
 {
  // counter to iteratively decrement.
  int decrementCounter;

  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // iteratively decrement date.
  for (decrementCounter = 1; decrementCounter <= decrementNum; decrementCounter++)
  {
   newDate = decrementByMonth(newDate);
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }

 // returns the date by incrementing the given date by one month.
 // if a number if given, then multiple months are incremented.
 public Date incrementByMonth(Date date)
 {
  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // if date is already at end of valid range, then don't do
  // anything.
  if (!((newDate.getYear() == 137) && (newDate.getMonth() == 11)))
  {
   // if we are not at the end of the current year, then
   // just go to next month. Otherwise, change years also.
   if (newDate.getMonth() < 11)
   {
    // go to next month.
    newDate = new Date(newDate.getYear(), newDate.getMonth() + 1, newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds());
   } else
   {
    // go to next year.
    newDate = incrementByYear(newDate, 1);

    // go to the first month of the next year.
    newDate = new Date(newDate.getYear(), 0, newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds());
   }
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }
 public Date incrementByMonth(Date date, int incrementNum)
 {
  // counter to iteratively increment.
  int incrementCounter;

  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // iteratively increment date.
  for (incrementCounter = 1; incrementCounter <= incrementNum; incrementCounter++)
  {
   newDate = incrementByMonth(newDate);
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }

 // returns the date by decrementing the given date by one year.
 // if a number if given, then multiple years are decremented.
 public Date decrementByYear(Date date)
 {
  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // if date is already at beginning of valid range, then don't do
  // anything.
  if (!((newDate.getYear() == 70)))
  {
   // decrement the year.
   newDate = new Date(newDate.getYear() - 1, newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds());
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }
 public Date decrementByYear(Date date, int decrementNum)
 {
  // counter to iteratively decrement.
  int decrementCounter;

  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // iteratively decrement date.
  for (decrementCounter = 1; decrementCounter <= decrementNum; decrementCounter++)
  {
   newDate = decrementByYear(newDate);
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }

 // returns the date by incrementing the given date by one year.
 // if a number if given, then multiple years are incremented.
 public Date incrementByYear(Date date)
 {
  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // if date is already at end of valid range, then don't do
  // anything.
  if (!((newDate.getYear() == 137)))
  {
   // increment the year.
   newDate = new Date(newDate.getYear() + 1, newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds());
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }
 public Date incrementByYear(Date date, int incrementNum)
 {
  // counter to iteratively increment.
  int incrementCounter;

  // new date.
  Date newDate;

  // start date on given date.
  newDate = new Date(date.getYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds());

  // iteratively increment date.
  for (incrementCounter = 1; incrementCounter <= incrementNum; incrementCounter++)
  {
   newDate = incrementByYear(newDate);
  }

  return (new Date(newDate.getYear(), newDate.getMonth(), newDate.getDate(), newDate.getHours(), newDate.getMinutes(), newDate.getSeconds()));
 }

 // returns the first day of the week of the week the day is in.
 // NOTE: if the first day of the week is outside of the valid date
 //       values (01/01/1970 -> 12/31/2037) then it will just return
 //       (01/01/1970).
 public Date firstDayOfThisWeek(Date date)
 {
  // new first day of week.
  Date firstDayOfWeek;

  // create/set the first day of the week.
  firstDayOfWeek = new Date(date.getYear(), date.getMonth(), date.getDate(), 0, 0, 0);

  // get the first day of the week.
  firstDayOfWeek = decrementByDay(firstDayOfWeek, firstDayOfWeek.getDay());

  // return the first day of the week.
  return (new Date(firstDayOfWeek.getYear(), firstDayOfWeek.getMonth(), firstDayOfWeek.getDate(), firstDayOfWeek.getHours(), firstDayOfWeek.getMinutes(), firstDayOfWeek.getSeconds()));
 }

 // returns if one Date is greater than another.
 // if firstDate > secondDate.
 public boolean dateIsGreater(Date firstDate, Date secondDate)
 {
  if (firstDate.getYear() > secondDate.getYear())
  {
   return true;
  } else if (firstDate.getYear() < secondDate.getYear())
  {
   return false;
  }
  if (firstDate.getMonth() > secondDate.getMonth())
  {
   return true;
  } else if (firstDate.getMonth() < secondDate.getMonth())
  {
   return false;
  }
  if (firstDate.getDate() > secondDate.getDate())
  {
   return true;
  } else if (firstDate.getDate() < secondDate.getDate())
  {
   return false;
  }
  if (firstDate.getHours() > secondDate.getHours())
  {
   return true;
  } else if (firstDate.getHours() < secondDate.getHours())
  {
   return false;
  }
  if (firstDate.getMinutes() > secondDate.getMinutes())
  {
   return true;
  } else if (firstDate.getMinutes() < secondDate.getMinutes())
  {
   return false;
  }
  if (firstDate.getSeconds() > secondDate.getSeconds())
  {
   return true;
  } else if (firstDate.getSeconds() < secondDate.getSeconds())
  {
   return false;
  }

  // if we made it this far, probably less than or equal.
  return false;
 }

 // returns if one Date (Time) is greater than another.
 // if firstDate > secondDate.
 // this version does not compare the calendar day, only clock time.
 public boolean timeIsGreater(Date firstDate, Date secondDate)
 {
  if (firstDate.getHours() > secondDate.getHours())
  {
   return true;
  } else if (firstDate.getHours() < secondDate.getHours())
  {
   return false;
  }
  if (firstDate.getMinutes() > secondDate.getMinutes())
  {
   return true;
  } else if (firstDate.getMinutes() < secondDate.getMinutes())
  {
   return false;
  }
  if (firstDate.getSeconds() > secondDate.getSeconds())
  {
   return true;
  } else if (firstDate.getSeconds() < secondDate.getSeconds())
  {
   return false;
  }

  // if we made it this far, probably less than or equal.
  return false;
 }

 // returns if one Date is greater than or equal to another.
 // if firstDate >= secondDate.
 public boolean dateIsGreaterEqual(Date firstDate, Date secondDate)
 {
  // if already greater than, then just return.
  if (dateIsGreater(firstDate, secondDate))
  {
   return true;
  }

  // check for non-equality.
  if (firstDate.getYear() != secondDate.getYear())
  {
   return false;
  }
  if (firstDate.getMonth() != secondDate.getMonth())
  {
   return false;
  }
  if (firstDate.getDate() != secondDate.getDate())
  {
   return false;
  }
  if (firstDate.getHours() != secondDate.getHours())
  {
   return false;
  }
  if (firstDate.getMinutes() != secondDate.getMinutes())
  {
   return false;
  }
  if (firstDate.getSeconds() != secondDate.getSeconds())
  {
   return false;
  }

  // if we made it this far, probably equal.
  return true;
 }
}