A time-less Date class for basic date arithmetics
/*
* (C) 2004 - Geotechnical Software Services
*
* This code is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This code is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this program; if not, write to the Free
* Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
//package no.geosoft.cc.util;
import java.util.Date;
import java.util.Calendar;
import java.util.TimeZone;
import java.io.Serializable;
/**
* A time-less Date class for basic date arithmetics.
*
* Thanks to Paul Hill @ xmission.com for valuable contribution.
*
* @author Jacob Dreyer (<a href="mailto:jacob.dreyer@geosoft.no">jacob.dreyer@geosoft.no</a>)
*/
public class Day
implements Comparable, Cloneable, Serializable
{
protected Calendar calendar_;
/**
* Initialize the internal calendar instance.
*
* @param year Year of new day.
* @param month Month of new day.
* @param dayOfMonth Day of month of new day.
*/
private void initialize (int year, int month, int dayOfMonth)
{
calendar_ = Calendar.getInstance();
calendar_.setLenient (true);
calendar_.setFirstDayOfWeek (Calendar.MONDAY);
calendar_.setTimeZone (TimeZone.getTimeZone ("GMT"));
set (year, month, dayOfMonth);
}
/**
* Create a new day.
* The day is lenient meaning that illegal day parameters can be
* specified and results in a recomputed day with legal month/day
* values.
*
* @param year Year of new day.
* @param month Month of new day (0-11)
* @param dayOfMonth Day of month of new day (1-31)
*/
public Day (int year, int month, int dayOfMonth)
{
initialize (year, month, dayOfMonth);
}
/**
* Create a new day, specifying the year and the day of year.
* The day is lenient meaning that illegal day parameters can be
* specified and results in a recomputed day with legal month/day
* values.
*
* @param year Year of new day.
* @param dayOfYear 1=January 1, etc.
*/
public Day (int year, int dayOfYear)
{
initialize (year, Calendar.JANUARY, 1);
calendar_.set (Calendar.DAY_OF_YEAR, dayOfYear);
}
/**
* Create a new day representing the day of creation
* (according to the setting of the current machine).
*/
public Day()
{
// Now (in the currenct locale of the client machine)
Calendar calendar = Calendar.getInstance();
// Prune time part
initialize (calendar.get (Calendar.YEAR),
calendar.get (Calendar.MONTH),
calendar.get (Calendar.DAY_OF_MONTH));
}
/**
* Create a new day based on a java.util.Calendar instance.
* NOTE: The time component from calendar will be pruned.
*
* @param calendar Calendar instance to copy.
*/
public Day (Calendar calendar)
{
this (calendar.get (Calendar.YEAR),
calendar.get (Calendar.MONTH),
calendar.get (Calendar.DAY_OF_MONTH));
}
/**
* Create a new day based on a java.util.Date instance.
* NOTE: The time component from date will be pruned.
*
* @param date Date instance to copy.
*/
public Day (Date date)
{
// Create a calendar based on given date
Calendar calendar = Calendar.getInstance();
calendar.setTime (date);
// Extract date values and use these only
initialize (calendar.get (Calendar.YEAR),
calendar.get (Calendar.MONTH),
calendar.get (Calendar.DAY_OF_MONTH));
}
/**
* Create a new day based on a time value.
* Time is milliseconds since "the Epoch" (1.1.1970).
* NOTE: The time component from time will be pruned.
*
* @param time Milliseconds since "the Epoch".
*/
public Day (long time)
{
this (new Date (time));
}
/**
* Create a new day as a copy of the specified day.
*
* @param day Day to clone.
*/
public Day (Day day)
{
this (day.getYear(), day.getMonth(), day.getDayOfMonth());
}
/**
* Create a clone of this day.
*
* @return This day cloned.
*/
public Object clone()
{
return new Day (this);
}
/**
* A more explicit front-end to the Day() constructor which return a day
* object representing the day of creation.
*
* @return A day instance representing today.
*/
public static Day today()
{
return new Day();
}
/**
* Return a Calendar instance representing the same day
* as this instance. For use by secondary methods requiring
* java.util.Calendar as input.
*
* @return Calendar equivalent representing this day.
*/
public Calendar getCalendar()
{
return (Calendar) calendar_.clone();
}
/**
* Return a Date instance representing the same date
* as this instance. For use by secondary methods requiring
* java.util.Date as input.
*
* @return Date equivalent representing this day.
*/
public Date getDate()
{
return getCalendar().getTime();
}
/**
* Compare this day to the specified day. If object is
* not of type Day a ClassCastException is thrown.
*
* @param object Day object to compare to.
* @return @see Comparable#compareTo(Object)
* @throws ClassCastException If object is not of type Day.
*/
public int compareTo (Object object)
{
Day day = (Day) object;
return calendar_.getTime().compareTo (day.calendar_.getTime());
}
/**
* Return true if this day is after the specified day.
*
* @param date Day to compare to.
* @return True if this is after day, false otherwise.
*/
public boolean isAfter (Day day)
{
return calendar_.after (day.calendar_);
}
/**
* Return true if this day is before the specified day.
*
* @param date Day to compare to.
* @return True if this is before day, false otherwise.
*/
public boolean isBefore (Day day)
{
return calendar_.before (day.calendar_);
}
/**
* Return true if this day equals (represent the same date)
* as the specified day.
*
* @param date Day to compare to.
* @return True if this equals day, false otherwise.
*/
public boolean equals (Day day)
{
return calendar_.equals (day.calendar_);
}
/**
* Overload required as default definition of equals() has changed.
*
* @return A hash code value for this object.
*/
public int hashCode()
{
return calendar_.hashCode();
}
/**
* Set date of this day.
* The day is lenient meaning that illegal day parameters can be
* specified and results in a recomputed day with legal month/day
* values.
*
* @param year Year of this day.
* @param month Month of this day (0-11).
* @param dayOfMonth Day of month of this day (1-31).
*/
public void set (int year, int month, int dayOfMonth)
{
setYear (year);
setMonth (month);
setDayOfMonth (dayOfMonth);
}
/**
* Return year of this day.
*
* @return Year of this day.
*/
public int getYear()
{
return calendar_.get (Calendar.YEAR);
}
/**
* Set year of this day.
*
* @param year New year of this day.
*/
public void setYear (int year)
{
calendar_.set (Calendar.YEAR, year);
}
/**
* Return month of this day. The result must be compared to Calendar.JANUARY,
* Calendar.FEBRUARY, etc.
*
* @return Month of this day.
*/
public int getMonth()
{
return calendar_.get (Calendar.MONTH);
}
/**
* Return the 1-based month number of the month of this day.
* 1 = January, 2 = February and so on.
*
* @return Month number of this month
*/
public int getMonthNo()
{
// It is tempting to return getMonth() + 1 but this is conceptually
// wrong, as Calendar month is an enumeration and the values are tags
// only and can be anything.
switch (getMonth()) {
case Calendar.JANUARY : return 1;
case Calendar.FEBRUARY : return 2;
case Calendar.MARCH : return 3;
case Calendar.APRIL : return 4;
case Calendar.MAY : return 5;
case Calendar.JUNE : return 6;
case Calendar.JULY : return 7;
case Calendar.AUGUST : return 8;
case Calendar.SEPTEMBER : return 9;
case Calendar.OCTOBER : return 10;
case Calendar.NOVEMBER : return 11;
case Calendar.DECEMBER : return 12;
}
// This will never happen
return 0;
}
/**
* Set month of this day. January = 0, February = 1, etc.
* Illegal month values will result in a recomputation of
* year and a resetting of month to a valid value.
* I.e. setMonth(20), will add 1 year to day and set month
* to 8.
*
* @param month New month of this day.
*/
public void setMonth (int month)
{
calendar_.set (Calendar.MONTH, month);
}
/**
* Return day of month of this day.
* NOTE: First day of month is 1 (not 0).
*
* @return Day of month of this day.
*/
public int getDayOfMonth()
{
return calendar_.get (Calendar.DAY_OF_MONTH);
}
/**
* Set day of month of this date. 1=1st 2=2nd, etc.
* Illegal day values will result in a recomputation of
* month/year and a resetting of day to a valid value.
* I.e. setDayOfMonth(33), will add 1 month to date and
* set day to 5, 4, 3 or 2 depending on month/year.
*
* @param dayOfMonth New day of month of this day.
*/
public void setDayOfMonth (int dayOfMonth)
{
calendar_.set (Calendar.DAY_OF_MONTH, dayOfMonth);
}
/**
* Return the day number of year this day represents.
* January 1 = 1 and so on.
*
* @return day number of year.
*/
public int getDayOfYear()
{
return calendar_.get (Calendar.DAY_OF_YEAR);
}
/**
* Return the day of week of this day.
* NOTE: Must be compared to Calendar.MONDAY, TUSEDAY etc.
*
* @return Day of week of this day.
*/
public int getDayOfWeek()
{
return calendar_.get (Calendar.DAY_OF_WEEK);
}
/**
* Return the day number of week of this day, where
* Monday=1, Tuesday=2, ... Sunday=7.
*
* @return Day number of week of this day.
*/
public int getDayNumberOfWeek()
{
return getDayOfWeek() == Calendar.SUNDAY ?
7 : getDayOfWeek() - Calendar.SUNDAY;
}
/**
* Return the week number of year, this day
* belongs to. 1st=1 and so on.
*
* @return Week number of year of this day.
*/
public int getWeekOfYear()
{
return calendar_.get (Calendar.WEEK_OF_YEAR);
}
/**
* Add a number of days to this day. Subtracting a number of
* days can be done by a negative argument to addDays() or calling
* subtractDays() explicitly.
*
* @param nDays Number of days to add.
*/
public void addDays (int nDays)
{
calendar_.add (Calendar.DAY_OF_MONTH, nDays);
}
/**
* Subtract a number of days from this day
*
* @param nDays Number of days to subtract.
*/
public void subtractDays (int nDays)
{
addDays (-nDays);
}
/**
* Add a number of months to this day. The actual number of days added
* depends on the staring day. Subtracting a number of months can be done
* by a negative argument to addMonths() or calling subtactMonths()
* explicitly.
* NOTE: addMonth(n) m times will in general give a different result
* than addMonth(m*n). Add 1 month to January 31, 2005 will give
* February 28, 2005.
*
* @param nMonths Number of months to add.
*/
public void addMonths (int nMonths)
{
calendar_.add (Calendar.MONTH, nMonths);
}
/**
* Subtract a number of months from this day
* @see #addMonths(int).
*
* @param nDays Number of days to subtract.
*/
public void subtractMonths (int nMonths)
{
addMonths (-nMonths);
}
/**
* Add a number of years to this day. The actual
* number of days added depends on the starting day.
* Subtracting a number of years can be done by a negative argument to
* addYears() or calling subtractYears explicitly.
*
* @param nYears Number of years to add.
*/
public void addYears (int nYears)
{
calendar_.add (Calendar.YEAR, nYears);
}
/**
* Subtract a number of years from this day
* @see #addYears(int).
*
* @param nYears Number of years to subtract.
*/
public void subtractYears (int nYears)
{
addYears (-nYears);
}
/**
* Return the number of days in the year of this day.
*
* @return Number of days in this year.
*/
public int getDaysInYear()
{
return calendar_.getActualMaximum (Calendar.DAY_OF_YEAR);
}
/**
* Return true if the year of this day is a leap year.
*
* @return True if this year is a leap year, false otherwise.
*/
public boolean isLeapYear()
{
return getDaysInYear() == calendar_.getMaximum (Calendar.DAY_OF_YEAR);
}
/**
* Return true if the specified year is a leap year.
*
* @param year Year to check.
* @return True if specified year is leap year, false otherwise.
*/
public static boolean isLeapYear (int year)
{
return (new Day (year, Calendar.JANUARY, 1)).isLeapYear();
}
/**
* Return the number of days in the month of this day.
*
* @return Number of days in this month.
*/
public int getDaysInMonth()
{
return calendar_.getActualMaximum (Calendar.DAY_OF_MONTH);
}
/**
* Get default locale name of this day ("Monday", "Tuesday", etc.
*
* @return Name of day.
*/
public String getDayName()
{
switch (getDayOfWeek()) {
case Calendar.MONDAY : return "Monday";
case Calendar.TUESDAY : return "Tuesday";
case Calendar.WEDNESDAY : return "Wednesday";
case Calendar.THURSDAY : return "Thursday";
case Calendar.FRIDAY : return "Friday";
case Calendar.SATURDAY : return "Saturday";
case Calendar.SUNDAY : return "Sunday";
}
// This will never happen
return null;
}
/**
* Return number of days between two days.
* The method always returns a positive number of days.
*
* @param date The day to compare to.
* @return Number of days between this and day.
*/
public int daysBetween (Day day)
{
long millisBetween = Math.abs (calendar_.getTime().getTime() -
day.calendar_.getTime().getTime());
return (int) Math.round (millisBetween / (1000 * 60 * 60 * 24));
}
/**
* Find the n'th xxxxday of s specified month (for instance find 1st sunday
* of May 2006; findNthOfMonth (1, Calendar.SUNDAY, Calendar.MAY, 2006);
* Return null if the specified day doesn't exists.
*
* @param n Nth day to look for.
* @param dayOfWeek Day to look for (Calendar.XXXDAY).
* @param month Month to check (Calendar.XXX).
* @param year Year to check.
* @return Required Day (or null if non-existent)
* @throws ArrayIndexOutOfBoundsException if dyaOfWeek parameter
* doesn't represent a valid day.
*/
public static Day getNthOfMonth (int n, int dayOfWeek, int month, int year)
throws ArrayIndexOutOfBoundsException
{
// Validate the dayOfWeek argument
if (dayOfWeek < 0 || dayOfWeek > 6)
throw new ArrayIndexOutOfBoundsException (dayOfWeek);
Day first = new Day (year, month, 1);
int offset = dayOfWeek - first.getDayOfWeek();
if (offset < 0) offset = 7 + offset;
int dayNo = (n - 1) * 7 + offset + 1;
return dayNo > first.getDaysInMonth() ? null : new Day (year, month, dayNo);
}
/**
* Find the first of a specific day in a given month, for instance
* first Tuesday of May:
* getFirstOfMonth (Calendar.TUESDAY, Calendar.MAY, 2005);
*
* @param dayOfWeek Weekday to get.
* @param month Month of day to get.
* @param year Year of day to get.
* @return The requested day.
*/
public static Day getFirstOfMonth (int dayOfWeek, int month, int year)
{
return Day.getNthOfMonth (1, dayOfWeek, month, year);
}
/**
* Find the last of a specific day in a given month, for instance
* last Tuesday of May:
* getLastOfMonth (Calendar.TUESDAY, Calendar.MAY, 2005);
*
* @param dayOfWeek Weekday to get.
* @param month Month of day to get.
* @param year Year of day to get.
* @return The requested day.
*/
public static Day getLastOfMonth (int dayOfWeek, int month, int year)
{
Day day = Day.getNthOfMonth (5, dayOfWeek, month, year);
return day != null ? day : Day.getNthOfMonth (4, dayOfWeek, month, year);
}
/**
* Return a scratch string representation of this day.
* Used for debugging only. The format of the
* day is dd/mm-yyyy
*
* @return A string representation of this day.
*/
public String toString()
{
StringBuffer string = new StringBuffer();
if (getDayOfMonth() < 10) string.append ('0');
string.append (getDayOfMonth());
string.append ('/');
if (getMonth() < 9) string.append ('0');
string.append (getMonth()+1);
string.append ('-');
string.append (getYear());
string.append (" ");
string.append (getDayName());
return string.toString();
}
/**
* Testing this class.
*
* @param args Not used.
*/
public static void main (String[] args)
{
// This proves that there are 912 days between the two major
// terrorist attacks, not 911 as is common knowledge.
Day september11 = new Day (2001, Calendar.SEPTEMBER, 11);
Day march11 = new Day (2004, Calendar.MARCH, 11);
System.out.println (september11.daysBetween (march11));
// This proves that Kennedy was president for 1037 days,
// not 1000 as is the popular belief nor 1036 which is the
// bluffers reply. Nerds knows when to add one...
Day precidency = new Day (1961, Calendar.JANUARY, 20);
Day assasination = new Day (1963, Calendar.NOVEMBER, 22);
System.out.println (precidency.daysBetween (assasination) + 1);
// Niel Armstrong walked the moon on a Sunday
Day nielOnMoon = new Day (1969, Calendar.JULY, 20);
System.out.println (nielOnMoon.getDayNumberOfWeek());
// Find last tuesdays for 2005
for (int i = 0; i < 12; i++) {
Day tuesday = Day.getLastOfMonth (Calendar.TUESDAY, i, 2005);
System.out.println (tuesday);
}
}
}
| 1. | A class representing a moment in time |