Java examples for java.util:Year
Adjusts the Calendar to the end of the day of the first day in DST in the current year or unchanged if not using DST.
/*//from w ww . j a v a 2s .co m * $Id: CalendarUtils.java 3916 2011-01-12 10:21:58Z kleopatra $ * * Copyright 2007 Sun Microsystems, Inc., 4150 Network Circle, * Santa Clara, California 95054, U.S.A. All rights reserved. * * This library 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 library 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 library; if not, write to the Free Software * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ //package com.java2s; import java.util.Calendar; import java.util.Date; public class Main { public static void main(String[] argv) throws Exception { Calendar calendar = Calendar.getInstance(); System.out.println(getStartOfDST(calendar)); } public static final int DECADE = 5467; public static final int YEAR_IN_DECADE = DECADE + 1; /** * Adjusts the Calendar to the end of the day of the first day in DST in the * current year or unchanged if not using DST. Returns the calendar's date or null, if not * using DST.<p> * * Note: the start of the day of the first day in DST is ill-defined! * * @param calendar the calendar to adjust * @return the start of day of the first day in DST, or null if not using DST. */ public static Date getStartOfDST(Calendar calendar) { if (!calendar.getTimeZone().useDaylightTime()) return null; long old = calendar.getTimeInMillis(); calendar.set(Calendar.MONTH, Calendar.JANUARY); startOfMonth(calendar); endOfDay(calendar); for (int i = 0; i < 366; i++) { calendar.add(Calendar.DATE, 1); if (calendar.getTimeZone().inDaylightTime(calendar.getTime())) { endOfDay(calendar); return calendar.getTime(); } } calendar.setTimeInMillis(old); return null; } /** * Sets the calendar field of the given calendar by amount. <p> * * NOTE: the custom field implementations are very naive (JSR-310 will do better) * - for decade: value must be positive, value must be a multiple of 10 and is interpreted as the * first-year-of-the-decade * - for year-in-decade: value is added/substracted to/from the start-of-decade of the * date of the given calendar * * @param calendar * @param field the field to increment, allowed are all fields known to * Calendar plus DECADE. * @param value the decade to set, must be a * * @throws IllegalArgumentException if the field is unsupported or the value is * not dividable by 10 or negative. */ public static void set(Calendar calendar, int field, int value) { if (isNativeField(field)) { calendar.set(field, value); } else { switch (field) { case DECADE: if (value <= 0) { throw new IllegalArgumentException( "value must be a positive but was: " + value); } if (value % 10 != 0) { throw new IllegalArgumentException( "value must be a multiple of 10 but was: " + value); } int yearInDecade = get(calendar, YEAR_IN_DECADE); calendar.set(Calendar.YEAR, value + yearInDecade); break; case YEAR_IN_DECADE: int decade = get(calendar, DECADE); calendar.set(Calendar.YEAR, value + decade); break; default: throw new IllegalArgumentException("unsupported field: " + field); } } } /** * Adjusts the calendar to the start of the current month. * That is, first day of the month with all time fields cleared. * * @param calendar calendar to adjust. */ public static void startOfMonth(Calendar calendar) { calendar.set(Calendar.DAY_OF_MONTH, 1); startOfDay(calendar); } /** * Adjust the given calendar to the last millisecond of the given date. * that is all time fields cleared. The Date of the adjusted Calendar is * returned. * * @param calendar calendar to adjust. * @param date the Date to use. * @return the end of the day of the given date */ public static Date endOfDay(Calendar calendar, Date date) { calendar.setTime(date); endOfDay(calendar); return calendar.getTime(); } /** * Adjust the given calendar to the last millisecond of the specified date. * * @param calendar calendar to adjust. */ public static void endOfDay(Calendar calendar) { calendar.add(Calendar.DATE, 1); startOfDay(calendar); calendar.add(Calendar.MILLISECOND, -1); } /** * Increments the calendar field of the given calendar by amount. * * @param calendar * @param field the field to increment, allowed are all fields known to * Calendar plus DECADE. * @param amount * * @throws IllegalArgumentException */ public static void add(Calendar calendar, int field, int amount) { if (isNativeField(field)) { calendar.add(field, amount); } else { switch (field) { case DECADE: calendar.add(Calendar.YEAR, amount * 10); break; default: throw new IllegalArgumentException("unsupported field: " + field); } } } /** * @param calendarField * @return */ private static boolean isNativeField(int calendarField) { return calendarField < DECADE; } /** * Gets the calendar field of the given calendar by amount. * * @param calendar * @param field the field to get, allowed are all fields known to * Calendar plus DECADE. * * @throws IllegalArgumentException */ public static int get(Calendar calendar, int field) { if (isNativeField(field)) { return calendar.get(field); } switch (field) { case DECADE: return decade(calendar.get(Calendar.YEAR)); case YEAR_IN_DECADE: return calendar.get(Calendar.YEAR) % 10; default: throw new IllegalArgumentException("unsupported field: " + field); } } /** * Adjust the given calendar to the first millisecond of the given date. * that is all time fields cleared. The Date of the adjusted Calendar is * returned. * * @param calendar calendar to adjust. * @param date the Date to use. * @return the start of the day of the given date */ public static Date startOfDay(Calendar calendar, Date date) { calendar.setTime(date); startOfDay(calendar); return calendar.getTime(); } /** * Adjust the given calendar to the first millisecond of the current day. * that is all time fields cleared. * * @param calendar calendar to adjust. */ public static void startOfDay(Calendar calendar) { calendar.set(Calendar.HOUR_OF_DAY, 0); calendar.set(Calendar.MILLISECOND, 0); calendar.set(Calendar.SECOND, 0); calendar.set(Calendar.MINUTE, 0); calendar.getTimeInMillis(); } /** * @param year * @return */ private static int decade(int year) { return (year / 10) * 10; } }