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Java example source code file (DateUtils.java)

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

Java tags/keywords

date, dateparseexception, default_patterns, default_two_digit_year_start, gmt, hashmap, hh:mm:ss, illegalargumentexception, mmm, pattern_asctime, pattern_rfc1123, simpledateformat, softreference, string, text, util

The DateUtils.java example source code

/*
 * ====================================================================
 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.http.impl.cookie;

import java.lang.ref.SoftReference;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;
import java.util.TimeZone;

import org.apache.http.annotation.Immutable;

/**
 * A utility class for parsing and formatting HTTP dates as used in cookies and 
 * other headers.  This class handles dates as defined by RFC 2616 section 
 * 3.3.1 as well as some other common non-standard formats.
 * 
 *
 * @since 4.0
 */
@Immutable
public final class DateUtils {

    /**
     * Date format pattern used to parse HTTP date headers in RFC 1123 format.
     */
    public static final String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";

    /**
     * Date format pattern used to parse HTTP date headers in RFC 1036 format.
     */
    public static final String PATTERN_RFC1036 = "EEEE, dd-MMM-yy HH:mm:ss zzz";

    /**
     * Date format pattern used to parse HTTP date headers in ANSI C 
     * <code>asctime() format.
     */
    public static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy";

    private static final String[] DEFAULT_PATTERNS = new String[] {
    	PATTERN_RFC1036,
    	PATTERN_RFC1123,
        PATTERN_ASCTIME
    };

    private static final Date DEFAULT_TWO_DIGIT_YEAR_START;
    
    public static final TimeZone GMT = TimeZone.getTimeZone("GMT");
    
    static {
        Calendar calendar = Calendar.getInstance();
        calendar.setTimeZone(GMT);
        calendar.set(2000, Calendar.JANUARY, 1, 0, 0, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        DEFAULT_TWO_DIGIT_YEAR_START = calendar.getTime(); 
    }
    
    /**
     * Parses a date value.  The formats used for parsing the date value are retrieved from
     * the default http params.
     *
     * @param dateValue the date value to parse
     * 
     * @return the parsed date
     *
     * @throws DateParseException if the value could not be parsed using any of the 
     * supported date formats
     */
    public static Date parseDate(String dateValue) throws DateParseException {
        return parseDate(dateValue, null, null);
    }
    
    /**
     * Parses the date value using the given date formats.
     * 
     * @param dateValue the date value to parse
     * @param dateFormats the date formats to use
     * 
     * @return the parsed date
     * 
     * @throws DateParseException if none of the dataFormats could parse the dateValue
     */
    public static Date parseDate(final String dateValue, String[] dateFormats) 
        throws DateParseException {
        return parseDate(dateValue, dateFormats, null);
    }
    
    /**
     * Parses the date value using the given date formats.
     * 
     * @param dateValue the date value to parse
     * @param dateFormats the date formats to use
     * @param startDate During parsing, two digit years will be placed in the range 
     * <code>startDate to startDate + 100 years. This value may 
     * be <code>null. When null is given as a parameter, year 
     * <code>2000 will be used. 
     * 
     * @return the parsed date
     * 
     * @throws DateParseException if none of the dataFormats could parse the dateValue
     */
    public static Date parseDate(
        String dateValue, 
        String[] dateFormats,
        Date startDate 
    ) throws DateParseException {
        
        if (dateValue == null) {
            throw new IllegalArgumentException("dateValue is null");
        }
        if (dateFormats == null) {
            dateFormats = DEFAULT_PATTERNS;
        }
        if (startDate == null) {
            startDate = DEFAULT_TWO_DIGIT_YEAR_START;
        }
        // trim single quotes around date if present
        // see issue #5279
        if (dateValue.length() > 1 
            && dateValue.startsWith("'") 
            && dateValue.endsWith("'")
        ) {
            dateValue = dateValue.substring (1, dateValue.length() - 1);
        }

        for (String dateFormat : dateFormats) {
            SimpleDateFormat dateParser = DateFormatHolder.formatFor(dateFormat);
            dateParser.set2DigitYearStart(startDate);

            try {
                return dateParser.parse(dateValue);
            } catch (ParseException pe) {
                // ignore this exception, we will try the next format
            }
        }
        
        // we were unable to parse the date
        throw new DateParseException("Unable to parse the date " + dateValue);        
    }

    /**
     * Formats the given date according to the RFC 1123 pattern.
     * 
     * @param date The date to format.
     * @return An RFC 1123 formatted date string.
     * 
     * @see #PATTERN_RFC1123
     */
    public static String formatDate(Date date) {
        return formatDate(date, PATTERN_RFC1123);
    }
    
    /**
     * Formats the given date according to the specified pattern.  The pattern
     * must conform to that used by the {@link SimpleDateFormat simple date
     * format} class.
     * 
     * @param date The date to format.
     * @param pattern The pattern to use for formatting the date.  
     * @return A formatted date string.
     * 
     * @throws IllegalArgumentException If the given date pattern is invalid.
     * 
     * @see SimpleDateFormat
     */
    public static String formatDate(Date date, String pattern) {
        if (date == null) throw new IllegalArgumentException("date is null");
        if (pattern == null) throw new IllegalArgumentException("pattern is null");
        
        SimpleDateFormat formatter = DateFormatHolder.formatFor(pattern);
        return formatter.format(date);
    }
    
    /** This class should not be instantiated. */    
    private DateUtils() { 
    }
    
    /**
     * A factory for {@link SimpleDateFormat}s. The instances are stored in a
     * threadlocal way because SimpleDateFormat is not threadsafe as noted in
     * {@link SimpleDateFormat its javadoc}.
     * 
     */
    final static class DateFormatHolder {

        private static final ThreadLocal<SoftReference> 
            THREADLOCAL_FORMATS = new ThreadLocal<SoftReference>() {

            @Override
            protected SoftReference<Map initialValue() {
                return new SoftReference<Map(
                        new HashMap<String, SimpleDateFormat>());
            }
            
        };

        /**
         * creates a {@link SimpleDateFormat} for the requested format string.
         * 
         * @param pattern
         *            a non-<code>null format String according to
         *            {@link SimpleDateFormat}. The format is not checked against
         *            <code>null since all paths go through
         *            {@link DateUtils}.
         * @return the requested format. This simple dateformat should not be used
         *         to {@link SimpleDateFormat#applyPattern(String) apply} to a
         *         different pattern.
         */
        public static SimpleDateFormat formatFor(String pattern) {
            SoftReference<Map ref = THREADLOCAL_FORMATS.get();
            Map<String, SimpleDateFormat> formats = ref.get();
            if (formats == null) {
                formats = new HashMap<String, SimpleDateFormat>();
                THREADLOCAL_FORMATS.set(
                        new SoftReference<Map(formats));    
            }

            SimpleDateFormat format = formats.get(pattern);
            if (format == null) {
                format = new SimpleDateFormat(pattern, Locale.US);
                format.setTimeZone(TimeZone.getTimeZone("GMT"));
                formats.put(pattern, format);
            }

            return format;
        }
        
    }
    
}

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