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 { //----------------------------------------------------------------------- /** * Adds a number of seconds to a date returning a new object. * The original date object is unchanged. * * @param date the date, not null * @param amount the amount to add, may be negative * @return the new date object with the amount added * @throws IllegalArgumentException if the date is null */ public static Date addSeconds(Date date, int amount) { return add(date, Calendar.SECOND, amount); } //----------------------------------------------------------------------- /** * Adds to a date returning a new object. * The original date object is unchanged. * * @param date the date, not null * @param calendarField the calendar field to add to * @param amount the amount to add, may be negative * @return the new date object with the amount added * @throws IllegalArgumentException if the date is null */ private static Date add(Date date, int calendarField, int amount) { if (date == null) { throw new IllegalArgumentException("The date must not be null"); } Calendar c = Calendar.getInstance(); c.setTime(date); c.add(calendarField, amount); return c.getTime(); } }