getting wrong values using matcher.group()

[vardhan reddy]

Hi All,
I am validating date using regex and I'm trying to get matcher groups and getting wrong values. Can anyone check and let me know what i'm doing wrong.

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class CheckDate {
	// private static final String DATE_PATTERN =
	// "((19|20)\\d\\d)(0?[1-9]|1[012])(0?[1-9]|[12][0-9]|3[01])";
	private static final String DATE_PATTERN = "((19|20)\\d\\d)(0[1-9]|1[012])(0?[1-9]|[12][0-9]|3[01])";
	private Pattern pattern;
	private Matcher matcher;

	public static void main(String[] args) {
		CheckDate date = new CheckDate();
		boolean flag = date.validate("20120131");
		System.out.println("date flag is::::::::::" + flag);
	}

	private boolean validate(String date) {
		pattern = Pattern.compile(DATE_PATTERN);
		matcher = pattern.matcher(date);
		if (matcher.matches()) {
			System.out.println("matched..................");
			matcher.reset();
			if (matcher.find()) {
				System.out.println(matcher.groupCount());
				System.out.println(matcher.group(1) + " and "
						+ matcher.group(2) + " and " + matcher.group(3)+" and "+matcher.group(4));
				int year = Integer.parseInt(date.substring(0, 4));
				String month = date.substring(4, 6);
				String day = date.substring(6, 8);

				if (day.equals("31")
						&& (month.equals("11") || month.equals("04")
								|| month.equals("06") || month.equals("09"))) {
					return false; // only 1,3,5,7,8,10,12 has 31 days
				} else if (month.equals("02")) {
					// leap year
					if (year % 4 == 0) {
						if (day.equals("30") || day.equals("31")) {
							return false;
						} else {
							return true;
						}
					} else {
						if (day.equals("29") || day.equals("30")
								|| day.equals("31")) {
							return false;
						} else {
							return true;
						}
					}
				} else {
					return true;
				}
			} else {
				return false;
			}
		} else {
			System.out.println("not matched..................");
			return false;
		}
	}
}

[Jelle Klap]

Someone is going to inevitably mention this, so it might as well be me: why not just use (Simple)DateFormat?

[vardhan reddy]

Hi,
I'm planning to write generic class to validate any date format and DATE_PATTERN regex will be passed to validate method based on date format.
By using DateFormat, if parse (date format yyyymmdd)

String date = "20121301";

I will get

Tue Jan 01 00:00:00 IST 2013

but which is wrong date(month is wrong).

thanks for your reply.

[Darryl Burke]

vardhan reddy wrote:By using DateFormat, if parse (date format yyyymmdd)

String date = "20121301";

I will get

Tue Jan 01 00:00:00 IST 2013

but which is wrong date(month is wrong).

No, it's right. What's the 1st day of the 13th month of 2012, with a lenient interpretation?

[vardhan reddy]

It will give 1st date of next month, but i dont want that date and I want to display warning message 'Invalide date' something like this.

[Jelle Klap]

Then you should disable lenient parsing, using the setLenient() method.