Validate Date against given Date Format

How to validate given Date against Date Format.

SO there are two approaches,

1.) Using SimpleDateFormat

2.) Using Regex.


Basic Example.

SimpleDateFormat 

Date date = null;
    boolean checkformat;
    try {
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy/dd/MM");
        dateFormat.setLenient(false);
        date = dateFormat.parse("2013/25/09");
    } catch (ParseException ex) {
        ex.printStackTrace();
    }
    if (date == null) {
        checkformat = false;
    } else {
        checkformat = true;
    }

    System.out.println(checkformat);

Regex based  

public static void main(String[] args) throws ParseException {
        String input = "2014/12/31";
        boolean checkformat;
        if (input.matches("([0-9]{4})/([0-9]{2})/([0-9]{2})")) // for yyyy/MM/dd format
            checkformat = true;
        else
            checkformat = false;

        System.out.println(checkformat);
    } 

Play around the {2}, {2}, {4} values inside curly braces to prepare regex.

Complexity Increases, let say i have many Date Formats.

public class DateUtil {

 

    // List of all date formats that we want to parse.

    // Add your own format here.

    private static List<SimpleDateFormat>;

            dateFormats = new ArrayList<SimpleDateFormat>() {{

            add(new SimpleDateFormat("M/dd/yyyy"));

            add(new SimpleDateFormat("dd.M.yyyy"));

            add(new SimpleDateFormat("M/dd/yyyy hh:mm:ss a"));

            add(new SimpleDateFormat("dd.M.yyyy hh:mm:ss a"));

            add(new SimpleDateFormat("dd.MMM.yyyy"));

            add(new SimpleDateFormat("dd-MMM-yyyy"));

        }

    };

 

   /**

     * Convert String with various formats into java.util.Date

     *

     * @param input

     *            Date as a string

     * @return java.util.Date object if input string is parsed

     *          successfully else returns null

     */

 

 

public static Date convertToDate(String input) {

        Date date = null;

        if(null == input) {

            return null;

        }

        for (SimpleDateFormat format : dateFormats) {

            try {

                format.setLenient(false);

                date = format.parse(input);

            } catch (ParseException e) {

                //Shhh.. try other formats

            }

            if (date != null) {

                break;

            }

        }

 

        return date;

    }

 

} 







// Test class to test out

public class TestDateUtil {

 

    public static void main(String[] args) {

        System.out.println("10/14/2012" + " = " + DateUtil.convertToDate("10/14/2012"));

        System.out.println("10-Jan-2012" + " = " + DateUtil.convertToDate("10-Jan-2012"));

        System.out.println("01.03.2002" + " = " + DateUtil.convertToDate("01.03.2002"));

        System.out.println("12/03/2010" + " = " + DateUtil.convertToDate("12/03/2010"));

        System.out.println("19.Feb.2011" + " = " + DateUtil.convertToDate("19.Feb.2011" ));

        System.out.println("4/20/2012" + " = " + DateUtil.convertToDate("4/20/2012"));

        System.out.println("some string" + " = " + DateUtil.convertToDate("some string"));

        System.out.println("123456" + " = " + DateUtil.convertToDate("123456"));

        System.out.println("null" + " = " + DateUtil.convertToDate(null));

 

    }  

}