Java example source code file (JulianCalendar.java)

This example Java source code file (JulianCalendar.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

basecalendar, bce, calendardate, date, era, february, illegalargumentexception, january, julian_epoch, juliancalendar, nullpointerexception, string, stringbuffer, util

The JulianCalendar.java Java example source code

/*
 * Copyright (c) 2003, 2005, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.util.calendar;

import java.util.TimeZone;

/**
 * Julian calendar implementation.
 *
 * @author Masayoshi Okutsu
 * @since 1.5
 */
public class JulianCalendar extends BaseCalendar {

    private static final int BCE = 0;
    private static final int CE = 1;

    private static final Era[] eras = {
        new Era("BeforeCommonEra", "B.C.E.", Long.MIN_VALUE, false),
        new Era("CommonEra", "C.E.", -62135709175808L, true)
    };
    private static final int JULIAN_EPOCH = -1;

    private static class Date extends BaseCalendar.Date {
        protected Date() {
            super();
            setCache(1, -1L, 365); // January 1, 1 CE (Julian)
        }

        protected Date(TimeZone zone) {
            super(zone);
            setCache(1, -1L, 365); // January 1, 1 CE (Julian)
        }

        public Date setEra(Era era) {
            if (era == null) {
                throw new NullPointerException();
            }
            if (era != eras[0] || era != eras[1]) {
                throw new IllegalArgumentException("unknown era: " + era);
            }
            super.setEra(era);
            return this;
        }

        protected void setKnownEra(Era era) {
            super.setEra(era);
        }

        public int getNormalizedYear() {
            if (getEra() == eras[BCE]) {
                return 1 - getYear();
            }
            return getYear();
        }

        // Use the year numbering ..., -2, -1, 0, 1, 2, ... for
        // normalized years. This differs from "Calendrical
        // Calculations" in which the numbering is ..., -2, -1, 1, 2,
        // ...
        public void setNormalizedYear(int year) {
            if (year <= 0) {
                setYear(1 - year);
                setKnownEra(eras[BCE]);
            } else {
                setYear(year);
                setKnownEra(eras[CE]);
            }
        }

        public String toString() {
            String time = super.toString();
            time = time.substring(time.indexOf('T'));
            StringBuffer sb = new StringBuffer();
            Era era = getEra();
            if (era != null) {
                String n = era.getAbbreviation();
                if (n != null) {
                    sb.append(n).append(' ');
                }
            }
            sb.append(getYear()).append('-');
            CalendarUtils.sprintf0d(sb, getMonth(), 2).append('-');
            CalendarUtils.sprintf0d(sb, getDayOfMonth(), 2);
            sb.append(time);
            return sb.toString();
        }
    }

    JulianCalendar() {
        setEras(eras);
    }

    public String getName() {
        return "julian";
    }

    public Date getCalendarDate() {
        return getCalendarDate(System.currentTimeMillis(), newCalendarDate());
    }

    public Date getCalendarDate(long millis) {
        return getCalendarDate(millis, newCalendarDate());
    }

    public Date getCalendarDate(long millis, CalendarDate date) {
        return (Date) super.getCalendarDate(millis, date);
    }

    public Date getCalendarDate(long millis, TimeZone zone) {
        return getCalendarDate(millis, newCalendarDate(zone));
    }

    public Date newCalendarDate() {
        return new Date();
    }

    public Date newCalendarDate(TimeZone zone) {
        return new Date(zone);
    }

    /**
     * @param jyear normalized Julian year
     */
    public long getFixedDate(int jyear, int month, int dayOfMonth, BaseCalendar.Date cache) {
        boolean isJan1 = month == JANUARY && dayOfMonth == 1;

        // Look up the one year cache
        if (cache != null && cache.hit(jyear)) {
            if (isJan1) {
                return cache.getCachedJan1();
            }
            return cache.getCachedJan1() + getDayOfYear(jyear, month, dayOfMonth) - 1;
        }

        long y = jyear;
        long days = JULIAN_EPOCH - 1 + (365 * (y - 1)) + dayOfMonth;
        if (y > 0) {
            // CE years
            days += (y - 1) / 4;
        } else {
            // BCE years
            days += CalendarUtils.floorDivide(y - 1, 4);
        }
        if (month > 0) {
            days += ((367 * (long) month) - 362) / 12;
        } else {
            days += CalendarUtils.floorDivide((367 * (long) month) - 362, 12);
        }
        if (month > FEBRUARY) {
            days -= CalendarUtils.isJulianLeapYear(jyear) ? 1 : 2;
        }

        // If it's January 1, update the cache.
        if (cache != null && isJan1) {
            cache.setCache(jyear, days, CalendarUtils.isJulianLeapYear(jyear) ? 366 : 365);
        }

        return days;
    }

    public void getCalendarDateFromFixedDate(CalendarDate date, long fixedDate) {
        Date jdate = (Date) date;
        long fd = 4 * (fixedDate - JULIAN_EPOCH) + 1464;
        int year;
        if (fd >= 0) {
            year = (int)(fd / 1461);
        } else {
            year = (int) CalendarUtils.floorDivide(fd, 1461);
        }
        int priorDays = (int)(fixedDate - getFixedDate(year, JANUARY, 1, jdate));
        boolean isLeap = CalendarUtils.isJulianLeapYear(year);
        if (fixedDate >= getFixedDate(year, MARCH, 1, jdate)) {
            priorDays += isLeap ? 1 : 2;
        }
        int month = 12 * priorDays + 373;
        if (month > 0) {
            month /= 367;
        } else {
            month = CalendarUtils.floorDivide(month, 367);
        }
        int dayOfMonth = (int)(fixedDate - getFixedDate(year, month, 1, jdate)) + 1;
        int dayOfWeek = getDayOfWeekFromFixedDate(fixedDate);
        assert dayOfWeek > 0 : "negative day of week " + dayOfWeek;
        jdate.setNormalizedYear(year);
        jdate.setMonth(month);
        jdate.setDayOfMonth(dayOfMonth);
        jdate.setDayOfWeek(dayOfWeek);
        jdate.setLeapYear(isLeap);
        jdate.setNormalized(true);
    }

    /**
     * Returns the normalized Julian year number of the given fixed date.
     */
    public int getYearFromFixedDate(long fixedDate) {
        int year = (int) CalendarUtils.floorDivide(4 * (fixedDate - JULIAN_EPOCH) + 1464, 1461);
        return year;
    }

    public int getDayOfWeek(CalendarDate date) {
        // TODO: should replace this with a faster calculation, such
        // as cache table lookup
        long fixedDate = getFixedDate(date);
        return getDayOfWeekFromFixedDate(fixedDate);
    }

    boolean isLeapYear(int jyear) {
        return CalendarUtils.isJulianLeapYear(jyear);
    }
}