Check if a string contains only date

Question

I have a string which can contain a date(yyyy-MM-dd) or date and time (yyyy-MM-dd HH:mm:ss) in respective formats.

I want to know which strings contains only date.

DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
System.out.println(dateFormat.parse("2015-02-02"));
System.out.println(dateFormat.parse("2015-02-02 23:23:23"));

In above code, both the strings are parsed successfully, whereas the format is same for only first.

Answer 1

I would use the overload of parse which takes a ParsePosition - you can then check the position afterwards:

import java.util.*;
import java.text.*;

public class Test {

    public static void main(String[] args) throws Exception {
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
        dateFormat.setLenient(false);
        System.out.println(parseFully(dateFormat, "2015-02-02"));
        System.out.println(parseFully(dateFormat, "2015-02-02 23:23:23"));
    }

    private static Date parseFully(DateFormat format, String text) 
          throws ParseException {
        ParsePosition position = new ParsePosition(0);
        Date date = format.parse(text, position);
        if (position.getIndex() == text.length()) {
            return date;
        }
        if (date == null) {
            throw new ParseException("Date could not be parsed: " + text,
                                     position.getErrorIndex());
        }
        throw new ParseException("Date was parsed incompletely: " + text,
                                 position.getIndex());
    }
}

Answer 2

public static void main(String[] args) {
        String dateOnly = "2015-02-02";
        String dateAndTimeOnly = "2015-02-02 23:23:23";
        System.out.println("Date Only = " + validateDateFormat(dateOnly));
        System.out.println("Date And time Only = " + validateDateFormat(dateAndTimeOnly));
    }

    public static boolean validateDateFormat(String input) {

        return input.matches("([0-9]{4})-([0-9]{2})-([0-9]{2})");
    }

output

Date Only = true
Date And time Only = false

Regex is self explanatory - Input will be separated by -, ist part([0-9]{4}) can contain 4 digit , 2nd part can contain 2 digit [0-9]{2}, so as 3rd.