Java Date Format Guess determineDateFormat(String dateString)

Description

Determine SimpleDateFormat pattern matching with the given date string.

License

Apache License

Parameter

Parameter	Description
dateString	The date string to determine the SimpleDateFormat pattern for.

Return

The matching SimpleDateFormat pattern, or null if format is unknown.

Declaration

public static String determineDateFormat(String dateString) 

Method Source Code

//package com.java2s;
/**//from   w ww  . j  a  v a2  s  .c  om
 * Copyright (C) 2016 Hurence (support@hurence.com)
 *
 * Licensed 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.
 */

import java.util.*;

public class Main {
    private static final Map<String, String> DATE_FORMAT_REGEXPS = new HashMap<String, String>() {
        {
            put("^[A-Z,a-z]{3}\\s[A-Z,a-z]{3}\\s\\d{1,2}\\s\\d{1,2}:\\d{1,2}:\\d{1,2}\\s[A-Z,a-z]{3}\\s\\d{4}$",
                    "EEE MMM dd hh:mm:ss zzz yyyy");
            put("^[A-Z,a-z]{3},\\s\\d{1,2}\\s[A-Z,a-z]{3}\\s\\d{4}\\s\\d{1,2}:\\d{1,2}:\\d{1,2}\\s[A-Z,a-z]{3}$",
                    "EEE, dd MMM yyyy HH:mm:ss z");
            put("^\\d{4}-\\d{2}-\\d{2}[T,t]\\d{2}:\\d{2}:\\d{2}\\.\\d{3}[A-Z,a-z]{3}$",
                    "yyyy-MM-dd'T'HH:mm:ss.SSSZ");
            put("^\\d{4}-\\d{2}-\\d{2}\\s\\d{2}:\\d{2}:\\d{2},\\d{3}$", "yyyy-MM-dd HH:mm:ss,SSS");
            put("^\\d{4}-\\d{2}-\\d{2}\\s\\d{2}:\\d{2}:\\d{2}\\.\\d{3}$", "yyyy-MM-dd HH:mm:ss.SSS");
            put("^\\d{4}-\\d{2}-\\d{2}[T,t]\\d{2}:\\d{2}:\\d{2}[A-Z,a-z]{3}$", "yyyy-MM-dd'T'HH:mm:ssz");
            put("^\\d{4}-\\d{1,2}-\\d{1,2}\\s\\d{1,2}:\\d{2}:\\d{2}$", "yyyy-MM-dd HH:mm:ss");
            put("^\\d{4}-\\d{2}-\\d{2}[T,t]\\d{2}:\\d{2}:\\d{2}\\.\\d{4}\\+\\d{2}:\\d{2}$",
                    "yyyy-MM-dd'T'HH:mm:ss.SSSSX");
            put("^\\d{8}$", "yyyyMMdd");
            put("^\\d{1,2}-\\d{1,2}-\\d{4}$", "dd-MM-yyyy");
            put("^\\d{4}-\\d{1,2}-\\d{1,2}$", "yyyy-MM-dd");
            put("^\\d{1,2}/\\d{1,2}/\\d{4}$", "MM/dd/yyyy");
            put("^\\d{4}/\\d{1,2}/\\d{1,2}$", "yyyy/MM/dd");
            put("^\\d{1,2}\\s[a-z]{3}\\s\\d{4}$", "dd MMM yyyy");
            put("^\\d{1,2}\\s[a-z]{4,}\\s\\d{4}$", "dd MMMM yyyy");
            put("^\\d{12}$", "yyyyMMddHHmm");
            put("^\\d{8}\\s\\d{4}$", "yyyyMMdd HHmm");
            put("^\\d{1,2}-\\d{1,2}-\\d{4}\\s\\d{1,2}:\\d{2}$", "dd-MM-yyyy HH:mm");
            put("^\\d{4}-\\d{1,2}-\\d{1,2}\\s\\d{1,2}:\\d{2}$", "yyyy-MM-dd HH:mm");
            put("^\\d{1,2}/\\d{1,2}/\\d{4}\\s\\d{1,2}:\\d{2}$", "dd/MM/yyyy HH:mm");
            put("^\\d{4}/\\d{1,2}/\\d{1,2}\\s\\d{1,2}:\\d{2}$", "yyyy/MM/dd HH:mm");
            put("^\\d{1,2}\\s[a-z]{3}\\s\\d{4}\\s\\d{1,2}:\\d{2}$", "dd MMM yyyy HH:mm");
            put("^\\d{1,2}\\s[a-z]{4,}\\s\\d{4}\\s\\d{1,2}:\\d{2}$", "dd MMMM yyyy HH:mm");
            put("^\\d{14}$", "yyyyMMddHHmmss");
            put("^\\d{8}\\s\\d{6}$", "yyyyMMdd HHmmss");
            put("^\\d{1,2}-\\d{1,2}-\\d{4}\\s\\d{1,2}:\\d{2}:\\d{2}$", "dd-MM-yyyy HH:mm:ss");

            put("^\\d{1,2}/\\d{1,2}/\\d{4}\\s\\d{1,2}:\\d{2}:\\d{2}$", "dd/MM/yyyy HH:mm:ss");
            put("^\\d{4}/\\d{1,2}/\\d{1,2}\\s\\d{1,2}:\\d{2}:\\d{2}$", "yyyy/MM/dd HH:mm:ss");
            put("^\\d{1,2}\\s[a-z]{3}\\s\\d{4}\\s\\d{1,2}:\\d{2}:\\d{2}$", "dd MMM yyyy HH:mm:ss");
            put("^\\d{1,2}\\s[a-z]{4,}\\s\\d{4}\\s\\d{1,2}:\\d{2}:\\d{2}$", "dd MMMM yyyy HH:mm:ss");

            put("^\\d{1,2}/\\w{3}/\\d{4}:\\d{2}:\\d{2}:\\d{2}\\s[-\\+]\\d{4}$", "dd/MMM/yyyy:HH:mm:ss Z"); //"02/JAN/2014:09:43:49 +0200"
            put("^\\w{3}\\s\\d{1,2}\\s\\d{1,2}:\\d{2}:\\d{2}$", "MMM dd HH:mm:ss"); // "Jan 02 07:43:49"
            put("^\\d{2}/\\d{2}/\\d{4}-\\d{2}:\\d{2}:\\d{2}:\\d{3}$", "dd/MM/yyyy-HH:mm:ss:SSS"); //'02/01/2016-07:43:49,000'
            put("^\\d{1,2}-\\w{3}-\\d{4}\\s\\d{2}:\\d{2}:\\d{2}:\\d{3}$", "dd-MMM-yyyy HH:mm:ss:SSS");
            put("^\\d{1,2}-\\w{3}-\\d{4}\\s\\d{2}:\\d{2}:\\d{2}.\\d{3}$", "dd-MMM-yyyy HH:mm:ss.SSS");
            put("^\\d{4}\\s+\\w{3}\\s+\\d{1,2}\\s+\\d{1,2}:\\d{1,2}:\\d{1,2}$", "yyyy MMM dd HH:mm:ss"); // '2017 Jan 17 18:52:18'
            put("^\\d{4}$", "yyyy"); // '2017'
        }
    };

    /**
     * Determine SimpleDateFormat pattern matching with the given date string. Returns null if
     * format is unknown. You can simply extend DateUtil with more formats if needed.
     * @param dateString The date string to determine the SimpleDateFormat pattern for.
     * @return The matching SimpleDateFormat pattern, or null if format is unknown.
     * @see SimpleDateFormat
     */
    public static String determineDateFormat(String dateString) {
        for (String regexp : DATE_FORMAT_REGEXPS.keySet()) {
            if (dateString.toLowerCase().matches(regexp)) {
                return DATE_FORMAT_REGEXPS.get(regexp);
            }
        }
        return null; // Unknown format.
    }
}

Related

1. determineDateFormat(String dateString)
2. determineDateFormat(String dateString)
3. getDateFormat(Date date)
4. getDateFormat(Date date, String format)