Java: Check the date format of current string is a

Question

This question already has answers here:

How to sanity check a date in Java [closed] (21 answers)

Closed 2 years ago.

I wanted to know that is there any method available in Java that can do this.Otherwise I may go for Regex solution.

I have input string from user that can be any characters. And I want to check that the input string is according to my required date format or not.

As I have input 20130925 and my required format is dd/MM/yyyy so, for this case I should get false.

I don't want to convert this date I just want to check whether input string is according to required date format or not.

I have tried following

Date date = null;
try {
date = new SimpleDateFormat("dd/MM/yyyy").parse("20130925");
} catch (Exception ex) {
// do something for invalid dateformat
}

but my catch (Exception ex) block is unable to catch any exceptions generated by SimpleDateFormat.Parse();

Answer 1

Here's a simple method:

public static boolean checkDatePattern(String padrao, String data) {
    try {
        SimpleDateFormat format = new SimpleDateFormat(padrao, LocaleUtils.DEFAULT_LOCALE);
        format.parse(data);
        return true;
    } catch (ParseException e) {
        return false;
    }
}

Answer 2

For example, if you want the date format to be "03.11.2017"

 if (String.valueOf(DateEdit.getText()).matches("([1-9]{1}|[0]{1}[1-9]{1}|[1]{1}[0-9]{1}|[2]{1}[0-9]{1}|[3]{1}[0-1]{1})" +
           "([.]{1})" +
           "([0]{1}[1-9]{1}|[1]{1}[0-2]{1}|[1-9]{1})" +
           "([.]{1})" +
           "([20]{2}[0-9]{2})"))
           checkFormat=true;
 else
           checkFormat=false;

 if (!checkFormat) {
 Toast.makeText(getApplicationContext(), "incorrect date format! Ex.23.06.2016", Toast.LENGTH_SHORT).show();
                }

Answer 3

You can try this to simple date format valdation

 public Date validateDateFormat(String dateToValdate) {

    SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy HHmmss");
    //To make strict date format validation
    formatter.setLenient(false);
    Date parsedDate = null;
    try {
        parsedDate = formatter.parse(dateToValdate);
        System.out.println("++validated DATE TIME ++"+formatter.format(parsedDate));

    } catch (ParseException e) {
        //Handle exception
    }
    return parsedDate;
}

Answer 4

A combination of the regex and SimpleDateFormat is the right answer i believe. SimpleDateFormat does not catch exception if the individual components are invalid meaning, Format Defined: yyyy-mm-dd input: 201-0-12 No exception will be thrown.This case should have been handled. But with the regex as suggested by Sok Pomaranczowy and Baby will take care of this particular case.

Answer 5

Regex can be used for this with some detailed info for validation, for example this code can be used to validate any date in (DD/MM/yyyy) format with proper date and month value and year between (1950-2050)

    public Boolean checkDateformat(String dateToCheck){   
        String rex="([0]{1}[1-9]{1}|[1-2]{1}[0-9]{1}|[3]{1}[0-1]{1})+
        \/([0]{1}[1-9]{1}|[1]{1}[0-2]{2})+
        \/([1]{1}[9]{1}[5-9]{1}[0-9]{1}|[2]{1}[0]{1}([0-4]{1}+
        [0-9]{1}|[5]{1}[0]{1}))";

        return(dateToCheck.matches(rex));
    }

Answer 6

Disclaimer

Parsing a string back to date/time value in an unknown format is inherently impossible (let's face it, what does 3/3/3 actually mean?!), all we can do is "best effort"

Important

This solution doesn't throw an Exception, it returns a boolean, this is by design. Any Exceptions are used purely as a guard mechanism.

2018

Since it's now 2018 and Java 8+ has the date/time API (and the rest have the ThreeTen backport). The solution remains basically the same, but becomes slightly more complicated, as we need to perform checks for:

• date and time
• date only
• time only

This makes it look something like...

public static boolean isValidFormat(String format, String value, Locale locale) {
    LocalDateTime ldt = null;
    DateTimeFormatter fomatter = DateTimeFormatter.ofPattern(format, locale);

    try {
        ldt = LocalDateTime.parse(value, fomatter);
        String result = ldt.format(fomatter);
        return result.equals(value);
    } catch (DateTimeParseException e) {
        try {
            LocalDate ld = LocalDate.parse(value, fomatter);
            String result = ld.format(fomatter);
            return result.equals(value);
        } catch (DateTimeParseException exp) {
            try {
                LocalTime lt = LocalTime.parse(value, fomatter);
                String result = lt.format(fomatter);
                return result.equals(value);
            } catch (DateTimeParseException e2) {
                // Debugging purposes
                //e2.printStackTrace();
            }
        }
    }

    return false;
}

This makes the following...

System.out.println("isValid - dd/MM/yyyy with 20130925 = " + isValidFormat("dd/MM/yyyy", "20130925", Locale.ENGLISH));
System.out.println("isValid - dd/MM/yyyy with 25/09/2013 = " + isValidFormat("dd/MM/yyyy", "25/09/2013", Locale.ENGLISH));
System.out.println("isValid - dd/MM/yyyy with 25/09/2013 12:13:50 = " + isValidFormat("dd/MM/yyyy", "25/09/2013  12:13:50", Locale.ENGLISH));
System.out.println("isValid - yyyy-MM-dd with 2017-18--15 = " + isValidFormat("yyyy-MM-dd", "2017-18--15", Locale.ENGLISH));

output...

isValid - dd/MM/yyyy with 20130925 = false
isValid - dd/MM/yyyy with 25/09/2013 = true
isValid - dd/MM/yyyy with 25/09/2013 12:13:50 = false
isValid - yyyy-MM-dd with 2017-18--15 = false

Original Answer

Simple try and parse the String to the required Date using something like SimpleDateFormat

Date date = null;
try {
    SimpleDateFormat sdf = new SimpleDateFormat(format);
    date = sdf.parse(value);
    if (!value.equals(sdf.format(date))) {
        date = null;
    }
} catch (ParseException ex) {
    ex.printStackTrace();
}
if (date == null) {
    // Invalid date format
} else {
    // Valid date format
}

You could then simply write a simple method that performed this action and returned true when ever Date was not null...

As a suggestion...

Updated with running example

I'm not sure what you are doing, but, the following example...

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

public class TestDateParser {

    public static void main(String[] args) {
        System.out.println("isValid - dd/MM/yyyy with 20130925 = " + isValidFormat("dd/MM/yyyy", "20130925"));
        System.out.println("isValid - dd/MM/yyyy with 25/09/2013 = " + isValidFormat("dd/MM/yyyy", "25/09/2013"));
        System.out.println("isValid - dd/MM/yyyy with 25/09/2013 12:13:50 = " + isValidFormat("dd/MM/yyyy", "25/09/2013  12:13:50"));
    }

    public static boolean isValidFormat(String format, String value) {
        Date date = null;
        try {
            SimpleDateFormat sdf = new SimpleDateFormat(format);
            date = sdf.parse(value);
            if (!value.equals(sdf.format(date))) {
                date = null;
            }
        } catch (ParseException ex) {
            ex.printStackTrace();
        }
        return date != null;
    }

}

Outputs (something like)...

java.text.ParseException: Unparseable date: "20130925"
isValid - dd/MM/yyyy with 20130925 = false
isValid - dd/MM/yyyy with 25/09/2013 = true
isValid - dd/MM/yyyy with 25/09/2013 12:13:50 = false
    at java.text.DateFormat.parse(DateFormat.java:366)
    at javaapplication373.JavaApplication373.isValidFormat(JavaApplication373.java:28)
    at javaapplication373.JavaApplication373.main(JavaApplication373.java:19)

Not correct. For isValidFormat("yyyy-MM-dd", "2017-18--15"); not throw any Exception.

isValid - yyyy-MM-dd", "2017-18--15 = false

Seems to work as expected for me - the method doesn't rely on (nor does it throw) the exception alone to perform it's operation