Java Date Value Check isValidDate(String dateString, String dateFormat)

Description

Checks whether the actual date of the given date string is valid based on the given date format pattern.

License

Open Source License

Parameter

Parameter	Description
dateString	The date string.
dateFormat	The date format pattern which should respect the SimpleDateFormat rules.

Return

True if the actual date of the given date string is valid based on the given date format pattern.

Declaration

public static boolean isValidDate(String dateString, String dateFormat)

Method Source Code


//package com.java2s;
//License from project: Open Source License 

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;

public class Main {
    private static final Map<String, String> DATE_FORMAT_REGEXPS = new HashMap<String, String>() {
        /**//from w w  w .  j  a v  a2 s.  c  o  m
         *
         */
        private static final long serialVersionUID = 6531756172647031848L;

        {
            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}$", "yyyy-MM-dd HH:mm");
            put("^\\d{1,2}/\\d{1,2}/\\d{4}\\s\\d{1,2}:\\d{2}$", "MM/dd/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{4}-\\d{1,2}-\\d{1,2}\\s\\d{1,2}:\\d{2}:\\d{2}$", "yyyy-MM-dd HH:mm:ss");
            put("^\\d{1,2}/\\d{1,2}/\\d{4}\\s\\d{1,2}:\\d{2}:\\d{2}$", "MM/dd/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");
        }
    };

    /**
     * Checks whether the actual date of the given date string is valid. This makes use of the
     * {@link DateUtil#determineDateFormat(String)} to determine the SimpleDateFormat pattern to be
     * used for parsing.
     *
     * @param dateString The date string.
     * @return True if the actual date of the given date string is valid.
     */
    public static boolean isValidDate(String dateString) {
        try {
            parse(dateString);
            return true;
        } catch (ParseException e) {
            return false;
        }
    }

    /**
     * Checks whether the actual date of the given date string is valid based on the given date
     * format pattern.
     *
     * @param dateString The date string.
     * @param dateFormat The date format pattern which should respect the SimpleDateFormat rules.
     * @return True if the actual date of the given date string is valid based on the given date
     * format pattern.
     * @see SimpleDateFormat
     */
    public static boolean isValidDate(String dateString, String dateFormat) {
        try {
            parse(dateString, dateFormat);
            return true;
        } catch (ParseException e) {
            return false;
        }
    }

    /**
     * Parse the given date string to date object and return a date instance based on the given
     * date string. This makes use of the {@link DateUtil#determineDateFormat(String)} to determine
     * the SimpleDateFormat pattern to be used for parsing.
     *
     * @param dateString The date string to be parsed to date object.
     * @return The parsed date object.
     * @throws ParseException If the date format pattern of the given date string is unknown, or if
     *                        the given date string or its actual date is invalid based on the date format pattern.
     */
    private static Date parse(String dateString) throws ParseException {
        String dateFormat = determineDateFormat(dateString);
        if (dateFormat == null) {
            throw new ParseException("Unknown date format.", 0);
        }
        return parse(dateString, dateFormat);
    }

    /**
     * Validate the actual date of the given date string based on the given date format pattern and
     * return a date instance based on the given date string.
     *
     * @param dateString The date string.
     * @param dateFormat The date format pattern which should respect the SimpleDateFormat rules.
     * @return The parsed date object.
     * @throws ParseException If the given date string or its actual date is invalid based on the
     *                        given date format pattern.
     * @see SimpleDateFormat
     */
    private static Date parse(String dateString, String dateFormat) throws ParseException {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat(dateFormat);
        simpleDateFormat.setLenient(false); // Don't automatically convert invalid date.
        return simpleDateFormat.parse(dateString);
    }

    /**
     * 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
     */
    private 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.
    }
}