Java tutorial
import java.util.Calendar; import java.util.Date; /** * 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 { 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 } }; /** * <p>Round this date, leaving the field specified as the most * significant field.</p> * * <p>For example, if you had the datetime of 28 Mar 2002 * 13:45:01.231, if this was passed with HOUR, it would return * 28 Mar 2002 14:00:00.000. If this was passed with MONTH, it * would return 1 April 2002 0:00:00.000.</p> * * <p>For a date in a timezone that handles the change to daylight * saving time, rounding to Calendar.HOUR_OF_DAY will behave as follows. * Suppose daylight saving time begins at 02:00 on March 30. Rounding a * date that crosses this time would produce the following values: * <ul> * <li>March 30, 2003 01:10 rounds to March 30, 2003 01:00</li> * <li>March 30, 2003 01:40 rounds to March 30, 2003 03:00</li> * <li>March 30, 2003 02:10 rounds to March 30, 2003 03:00</li> * <li>March 30, 2003 02:40 rounds to March 30, 2003 04:00</li> * </ul> * </p> * * @param date the date to work with * @param field the field from <code>Calendar</code> * or <code>SEMI_MONTH</code> * @return the rounded date (a different object) * @throws IllegalArgumentException if the date is <code>null</code> * @throws ArithmeticException if the year is over 280 million */ public static Calendar round(Calendar date, int field) { if (date == null) { throw new IllegalArgumentException("The date must not be null"); } Calendar rounded = (Calendar) date.clone(); modify(rounded, field, true); return rounded; } //----------------------------------------------------------------------- /** * <p>Internal calculation method.</p> * * @param val the calendar * @param field the field constant * @param round true to round, false to truncate * @throws ArithmeticException if the year is over 280 million */ private static void modify(Calendar val, int field, boolean round) { if (val.get(Calendar.YEAR) > 280000000) { throw new ArithmeticException("Calendar value too large for accurate calculations"); } if (field == Calendar.MILLISECOND) { return; } // ----------------- Fix for LANG-59 ---------------------- START --------------- // see http://issues.apache.org/jira/browse/LANG-59 // // Manually truncate milliseconds, seconds and minutes, rather than using // Calendar methods. Date date = val.getTime(); long time = date.getTime(); boolean done = false; // truncate milliseconds int millisecs = val.get(Calendar.MILLISECOND); if (!round || millisecs < 500) { time = time - millisecs; } if (field == Calendar.SECOND) { done = true; } // truncate seconds int seconds = val.get(Calendar.SECOND); if (!done && (!round || seconds < 30)) { time = time - (seconds * 1000L); } if (field == Calendar.MINUTE) { done = true; } // truncate minutes int minutes = val.get(Calendar.MINUTE); if (!done && (!round || minutes < 30)) { time = time - (minutes * 60000L); } // reset time if (date.getTime() != time) { date.setTime(time); val.setTime(date); } // ----------------- Fix for LANG-59 ----------------------- END ---------------- boolean roundUp = false; for (int i = 0; i < fields.length; i++) { for (int j = 0; j < fields[i].length; j++) { if (fields[i][j] == field) { //This is our field... we stop looping if (round && roundUp) { if (field == DateUtils.SEMI_MONTH) { //This is a special case that's hard to generalize //If the date is 1, we round up to 16, otherwise // we subtract 15 days and add 1 month if (val.get(Calendar.DATE) == 1) { val.add(Calendar.DATE, 15); } else { val.add(Calendar.DATE, -15); val.add(Calendar.MONTH, 1); } } else { //We need at add one to this field since the // last number causes us to round up val.add(fields[i][0], 1); } } return; } } //We have various fields that are not easy roundings int offset = 0; boolean offsetSet = false; //These are special types of fields that require different rounding rules switch (field) { case DateUtils.SEMI_MONTH: if (fields[i][0] == Calendar.DATE) { //If we're going to drop the DATE field's value, // we want to do this our own way. //We need to subtrace 1 since the date has a minimum of 1 offset = val.get(Calendar.DATE) - 1; //If we're above 15 days adjustment, that means we're in the // bottom half of the month and should stay accordingly. if (offset >= 15) { offset -= 15; } //Record whether we're in the top or bottom half of that range roundUp = offset > 7; offsetSet = true; } break; case Calendar.AM_PM: if (fields[i][0] == Calendar.HOUR_OF_DAY) { //If we're going to drop the HOUR field's value, // we want to do this our own way. offset = val.get(Calendar.HOUR_OF_DAY); if (offset >= 12) { offset -= 12; } roundUp = offset > 6; offsetSet = true; } break; } if (!offsetSet) { int min = val.getActualMinimum(fields[i][0]); int max = val.getActualMaximum(fields[i][0]); //Calculate the offset from the minimum allowed value offset = val.get(fields[i][0]) - min; //Set roundUp if this is more than half way between the minimum and maximum roundUp = offset > ((max - min) / 2); } //We need to remove this field if (offset != 0) { val.set(fields[i][0], val.get(fields[i][0]) - offset); } } throw new IllegalArgumentException("The field " + field + " is not supported"); } }