Java tutorial
import java.util.Calendar; import java.util.Date; import java.util.Iterator; import java.util.TimeZone; /** * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /** * <p>A suite of utilities surrounding the use of the * {@link java.util.Calendar} and {@link java.util.Date} object.</p> * * <p>DateUtils contains a lot of common methods considering manipulations * of Dates or Calendars. Some methods require some extra explanation. * The truncate and round methods could be considered the Math.floor(), * Math.ceil() or Math.round versions for dates * This way date-fields will be ignored in bottom-up order. * As a complement to these methods we've introduced some fragment-methods. * With these methods the Date-fields will be ignored in top-down order. * Since a date without a year is not a valid date, you have to decide in what * kind of date-field you want your result, for instance milliseconds or days. * </p> * * * * @author <a href="mailto:sergek@lokitech.com">Serge Knystautas</a> * @author Stephen Colebourne * @author Janek Bogucki * @author <a href="mailto:ggregory@seagullsw.com">Gary Gregory</a> * @author Phil Steitz * @author Robert Scholte * @since 2.0 * @version $Id: DateUtils.java 634096 2008-03-06 00:58:11Z niallp $ */ public class Main { /** * The UTC time zone (often referred to as GMT). */ public static final TimeZone UTC_TIME_ZONE = TimeZone.getTimeZone("GMT"); /** * Number of milliseconds in a standard second. * @since 2.1 */ public static final long MILLIS_PER_SECOND = 1000; /** * Number of milliseconds in a standard minute. * @since 2.1 */ public static final long MILLIS_PER_MINUTE = 60 * MILLIS_PER_SECOND; /** * Number of milliseconds in a standard hour. * @since 2.1 */ public static final long MILLIS_PER_HOUR = 60 * MILLIS_PER_MINUTE; /** * Number of milliseconds in a standard day. * @since 2.1 */ public static final long MILLIS_PER_DAY = 24 * MILLIS_PER_HOUR; /** * This is half a month, so this represents whether a date is in the top * or bottom half of the month. */ public final static int SEMI_MONTH = 1001; private static final int[][] fields = { { Calendar.MILLISECOND }, { Calendar.SECOND }, { Calendar.MINUTE }, { Calendar.HOUR_OF_DAY, Calendar.HOUR }, { Calendar.DATE, Calendar.DAY_OF_MONTH, Calendar.AM_PM /* Calendar.DAY_OF_YEAR, Calendar.DAY_OF_WEEK, Calendar.DAY_OF_WEEK_IN_MONTH */ }, { Calendar.MONTH, DateUtils.SEMI_MONTH }, { Calendar.YEAR }, { Calendar.ERA } }; /** * A week range, starting on Sunday. */ public final static int RANGE_WEEK_SUNDAY = 1; /** * A week range, starting on Monday. */ public final static int RANGE_WEEK_MONDAY = 2; /** * A week range, starting on the day focused. */ public final static int RANGE_WEEK_RELATIVE = 3; /** * A week range, centered around the day focused. */ public final static int RANGE_WEEK_CENTER = 4; /** * A month range, the week starting on Sunday. */ public final static int RANGE_MONTH_SUNDAY = 5; /** * A month range, the week starting on Monday. */ public final static int RANGE_MONTH_MONDAY = 6; /** * <p>Returns the number of days within the * fragment. All datefields greater than the fragment will be ignored.</p> * * <p>Asking the days of any date will only return the number of days * of the current month (resulting in a number between 1 and 31). This * method will retrieve the number of days for any fragment. * For example, if you want to calculate the number of days past this year, * your fragment is Calendar.YEAR. The result will be all days of the * past month(s).</p> * * <p>Valid fragments are: Calendar.YEAR, Calendar.MONTH, both * Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY, * Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND * A fragment less than or equal to a DAY field will return 0.</p> * * <p> * <ul> * <li>January 28, 2008 with Calendar.MONTH as fragment will return 28 * (equivalent to calendar.get(Calendar.DAY_OF_MONTH))</li> * <li>February 28, 2008 with Calendar.MONTH as fragment will return 28 * (equivalent to calendar.get(Calendar.DAY_OF_MONTH))</li> * <li>January 28, 2008 with Calendar.YEAR as fragment will return 28 * (equivalent to calendar.get(Calendar.DAY_OF_YEAR))</li> * <li>February 28, 2008 with Calendar.YEAR as fragment will return 59 * (equivalent to calendar.get(Calendar.DAY_OF_YEAR))</li> * <li>January 28, 2008 with Calendar.MILLISECOND as fragment will return 0 * (a millisecond cannot be split in days)</li> * </ul> * </p> * * @param calendar the calendar to work with, not null * @param fragment the Calendar field part of calendar to calculate * @return number of days within the fragment of date * @throws IllegalArgumentException if the date is <code>null</code> or * fragment is not supported * @since 2.4 */ public static long getFragmentInDays(Calendar calendar, int fragment) { return getFragment(calendar, fragment, Calendar.DAY_OF_YEAR); } /** * Date-version for fragment-calculation in any unit * * @param date the date to work with, not null * @param fragment the Calendar field part of date to calculate * @param unit Calendar field defining the unit * @return number of units within the fragment of the date * @throws IllegalArgumentException if the date is <code>null</code> or * fragment is not supported * @since 2.4 */ private static long getFragment(Date date, int fragment, int unit) { if (date == null) { throw new IllegalArgumentException("The date must not be null"); } Calendar calendar = Calendar.getInstance(); calendar.setTime(date); return getFragment(calendar, fragment, unit); } /** * Calendar-version for fragment-calculation in any unit * * @param calendar the calendar to work with, not null * @param fragment the Calendar field part of calendar to calculate * @param unit Calendar field defining the unit * @return number of units within the fragment of the calendar * @throws IllegalArgumentException if the date is <code>null</code> or * fragment is not supported * @since 2.4 */ private static long getFragment(Calendar calendar, int fragment, int unit) { if (calendar == null) { throw new IllegalArgumentException("The date must not be null"); } long millisPerUnit = getMillisPerUnit(unit); long result = 0; // Fragments bigger than a day require a breakdown to days switch (fragment) { case Calendar.YEAR: result += (calendar.get(Calendar.DAY_OF_YEAR) * MILLIS_PER_DAY) / millisPerUnit; break; case Calendar.MONTH: result += (calendar.get(Calendar.DAY_OF_MONTH) * MILLIS_PER_DAY) / millisPerUnit; break; } switch (fragment) { // Number of days already calculated for these cases case Calendar.YEAR: case Calendar.MONTH: // The rest of the valid cases case Calendar.DAY_OF_YEAR: case Calendar.DATE: result += (calendar.get(Calendar.HOUR_OF_DAY) * MILLIS_PER_HOUR) / millisPerUnit; case Calendar.HOUR_OF_DAY: result += (calendar.get(Calendar.MINUTE) * MILLIS_PER_MINUTE) / millisPerUnit; case Calendar.MINUTE: result += (calendar.get(Calendar.SECOND) * MILLIS_PER_SECOND) / millisPerUnit; case Calendar.SECOND: result += (calendar.get(Calendar.MILLISECOND) * 1) / millisPerUnit; break; case Calendar.MILLISECOND: break;//never useful default: throw new IllegalArgumentException("The fragment " + fragment + " is not supported"); } return result; } /** * Returns the number of millis of a datefield, if this is a constant value * * @param unit A Calendar field which is a valid unit for a fragment * @return number of millis * @throws IllegalArgumentException if date can't be represented in millisenconds * @since 2.4 */ private static long getMillisPerUnit(int unit) { long result = Long.MAX_VALUE; switch (unit) { case Calendar.DAY_OF_YEAR: case Calendar.DATE: result = MILLIS_PER_DAY; break; case Calendar.HOUR_OF_DAY: result = MILLIS_PER_HOUR; break; case Calendar.MINUTE: result = MILLIS_PER_MINUTE; break; case Calendar.SECOND: result = MILLIS_PER_SECOND; break; case Calendar.MILLISECOND: result = 1; break; default: throw new IllegalArgumentException("The unit " + unit + " cannot be represented is milleseconds"); } return result; } }