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A Java library for reading and writing iCalendar (*.ics) files
/**
* Copyright (c) 2012, Ben Fortuna
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* o Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* o Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* o Neither the name of Ben Fortuna nor the names of any other contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package net.fortuna.ical4j.util;
import net.fortuna.ical4j.model.Date;
import net.fortuna.ical4j.model.DateList;
import net.fortuna.ical4j.model.DateTime;
import net.fortuna.ical4j.model.parameter.Value;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
import java.util.TimeZone;
/**
* $Id$
*
* Created on 26/06/2005
*
* Implements a collection of utility methods relevant to date processing.
*
* @author Ben Fortuna
*/
public final class Dates {
/**
* Number of milliseconds in one second.
*/
public static final long MILLIS_PER_SECOND = 1000;
/**
* Number of milliseconds in one minute.
*/
public static final long MILLIS_PER_MINUTE = 60000;
/**
* Number of milliseconds in one hour.
*/
public static final long MILLIS_PER_HOUR = 3600000;
/**
* Number of milliseconds in one day.
*/
public static final long MILLIS_PER_DAY = 86400000;
/**
* Number of milliseconds in one week.
*/
public static final long MILLIS_PER_WEEK = 604800000;
/**
* Number of days in one week.
*/
public static final int DAYS_PER_WEEK = 7;
/**
* Constant indicating precision to the second.
*/
public static final int PRECISION_SECOND = 0;
/**
* Constant indicating precision to the day.
*/
public static final int PRECISION_DAY = 1;
/**
* Maximum number of weeks per year.
*/
public static final int MAX_WEEKS_PER_YEAR = 53;
/**
* Maximum number of days per year.
*/
public static final int MAX_DAYS_PER_YEAR = 366;
/**
* Maximum number of days per month.
*/
public static final int MAX_DAYS_PER_MONTH = 31;
private static final String INVALID_WEEK_MESSAGE = "Invalid week number [{0}]";
private static final String INVALID_YEAR_DAY_MESSAGE = "Invalid year day [{0}]";
private static final String INVALID_MONTH_DAY_MESSAGE = "Invalid month day [{0}]";
/**
* Constructor made private to prevent instantiation.
*/
private Dates() {
}
/**
* Returns the absolute week number for the year specified by the
* supplied date. Note that a value of zero (0) is invalid for the
* weekNo parameter and an IllegalArgumentException
* will be thrown.
* @param date a date instance representing a week of the year
* @param weekNo a week number offset
* @return the absolute week of the year for the specified offset
*/
public static int getAbsWeekNo(final java.util.Date date, final int weekNo) {
if (weekNo == 0 || weekNo < -MAX_WEEKS_PER_YEAR || weekNo > MAX_WEEKS_PER_YEAR) {
throw new IllegalArgumentException(MessageFormat.format(INVALID_WEEK_MESSAGE,
weekNo));
}
if (weekNo > 0) {
return weekNo;
}
final Calendar cal = Calendar.getInstance();
cal.setTime(date);
final int year = cal.get(Calendar.YEAR);
// construct a list of possible week numbers..
final List weeks = new ArrayList();
cal.set(Calendar.WEEK_OF_YEAR, 1);
while (cal.get(Calendar.YEAR) == year) {
weeks.add(cal.get(Calendar.WEEK_OF_YEAR));
cal.add(Calendar.WEEK_OF_YEAR, 1);
}
return weeks.get(weeks.size() + weekNo);
}
/**
* Returns the absolute year day for the year specified by the
* supplied date. Note that a value of zero (0) is invalid for the
* yearDay parameter and an IllegalArgumentException
* will be thrown.
* @param date a date instance representing a day of the year
* @param yearDay a day of year offset
* @return the absolute day of month for the specified offset
*/
public static int getAbsYearDay(final java.util.Date date, final int yearDay) {
if (yearDay == 0 || yearDay < -MAX_DAYS_PER_YEAR || yearDay > MAX_DAYS_PER_YEAR) {
throw new IllegalArgumentException(MessageFormat.format(INVALID_YEAR_DAY_MESSAGE,
yearDay));
}
if (yearDay > 0) {
return yearDay;
}
final Calendar cal = Calendar.getInstance();
cal.setTime(date);
final int year = cal.get(Calendar.YEAR);
// construct a list of possible year days..
final List days = new ArrayList();
cal.set(Calendar.DAY_OF_YEAR, 1);
while (cal.get(Calendar.YEAR) == year) {
days.add(cal.get(Calendar.DAY_OF_YEAR));
cal.add(Calendar.DAY_OF_YEAR, 1);
}
return days.get(days.size() + yearDay);
}
/**
* Returns the absolute month day for the month specified by the
* supplied date. Note that a value of zero (0) is invalid for the
* monthDay parameter and an IllegalArgumentException
* will be thrown.
* @param date a date instance representing a day of the month
* @param monthDay a day of month offset
* @return the absolute day of month for the specified offset
*/
public static int getAbsMonthDay(final java.util.Date date, final int monthDay) {
if (monthDay == 0 || monthDay < -MAX_DAYS_PER_MONTH || monthDay > MAX_DAYS_PER_MONTH) {
throw new IllegalArgumentException(MessageFormat.format(INVALID_MONTH_DAY_MESSAGE,
monthDay));
}
if (monthDay > 0) {
return monthDay;
}
final Calendar cal = Calendar.getInstance();
cal.setTime(date);
final int month = cal.get(Calendar.MONTH);
// construct a list of possible month days..
final List days = new ArrayList();
cal.set(Calendar.DAY_OF_MONTH, 1);
while (cal.get(Calendar.MONTH) == month) {
days.add(cal.get(Calendar.DAY_OF_MONTH));
cal.add(Calendar.DAY_OF_MONTH, 1);
}
return days.get(days.size() + monthDay);
}
/**
* Returns a new date instance of the specified type. If no type is
* specified a DateTime instance is returned.
* @param date a seed Java date instance
* @param type the type of date instance
* @return an instance of net.fortuna.ical4j.model.Date
*/
public static Date getInstance(final java.util.Date date, final Value type) {
if (Value.DATE.equals(type)) {
return new Date(date);
}
return new DateTime(date);
}
/**
* Returns an instance of java.util.Calendar that is suitably
* initialised for working with the specified date.
* @param date a date instance
* @return a java.util.Calendar
*/
public static Calendar getCalendarInstance(final Date date) {
Calendar instance;
if (date instanceof DateTime) {
final DateTime dateTime = (DateTime) date;
if (dateTime.getTimeZone() != null) {
instance = Calendar.getInstance(dateTime.getTimeZone());
}
else if (dateTime.isUtc()) {
instance = Calendar.getInstance(TimeZones.getUtcTimeZone());
}
else {
// a date-time without a timezone but not UTC is floating
instance = Calendar.getInstance();
}
}
else {
instance = Calendar.getInstance(TimeZones.getDateTimeZone());
}
return instance;
}
/**
* Instantiate a new datelist with the same type, timezone and utc settings
* as the origList.
*
* @param origList
* @return a new empty list.
*/
public static DateList getDateListInstance(final DateList origList) {
final DateList list = new DateList(origList.getType());
if (origList.isUtc()) {
list.setUtc(true);
} else {
list.setTimeZone(origList.getTimeZone());
}
return list;
}
/**
* @param time the time value to round
* @param precision the rounding precision
* @return a round time value
* @deprecated It is not all that useful to perform rounding without specifying an
* explicit timezone.
*/
public static long round(final long time, final int precision) {
return round(time, precision, TimeZone.getDefault());
// return round(time, precision, TimeZone.getTimeZone(TimeZones.UTC_ID));
/*
long newTime = time;
if (precision == PRECISION_DAY) {
long remainder = newTime%(1000*60*60); // get the mod remainder using milliseconds*seconds*min
newTime = newTime-remainder;
// remove the remainder from the time to clear the milliseconds, seconds and minutes
}
else if (precision == PRECISION_SECOND) {
long remainder = newTime%(1000); // get the mod remainder using milliseconds
newTime = newTime-remainder; // remove the remainder from the time to clear the milliseconds
}
return newTime;
*/
}
/**
* Rounds a time value to remove any precision smaller than specified.
* @param time the time value to round
* @param precision the rounding precision
* @param tz the timezone of the rounded value
* @return a round time value
*/
public static long round(final long time, final int precision, final TimeZone tz) {
if ((precision == PRECISION_SECOND) && ((time % Dates.MILLIS_PER_SECOND) == 0)) {
return time;
}
final Calendar cal = Calendar.getInstance(tz);
cal.setTimeInMillis(time);
if (precision == PRECISION_DAY) {
// return (long) Math.floor(time / (double) Dates.MILLIS_PER_DAY) * Dates.MILLIS_PER_DAY;
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.clear(Calendar.MINUTE);
cal.clear(Calendar.SECOND);
cal.clear(Calendar.MILLISECOND);
}
else if (precision == PRECISION_SECOND) {
// return (long) Math.floor(time / (double) Dates.MILLIS_PER_SECOND) * Dates.MILLIS_PER_SECOND;
cal.clear(Calendar.MILLISECOND);
}
// unrecognised precision..
return cal.getTimeInMillis();
}
/**
* Returns the {@code System.currentTimeMillis()}, rounded to the second.
* By doing a rough rounding here, we avoid an expensive java.util.Calendar based
* rounding later on.
* @return the current time in millisec.
*/
public static long getCurrentTimeRounded() {
return (long) Math.floor(System.currentTimeMillis() / (double) Dates.MILLIS_PER_SECOND) * Dates.MILLIS_PER_SECOND;
}
}
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