How to Validate a Date String Against a Specific Format in Java?

How to Check the Date Format of Current String Is According to Required Format in Java

Question:

Develop a Java method to validate if a user-inputted string matches a specified date format, considering both date-only and datetime formats.

Solution:

After evaluating various approaches, we settled on using the SimpleDateFormat class. Here's the detailed implementation:

<code class="java">import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateFormatter {

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

    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"));
        System.out.println("isValid - yyyy-MM-dd with 2017-18--15 = " + isValidFormat("yyyy-MM-dd", "2017-18--15"));
    }
}</code>

Usage:

Pass the required date format as the first argument and the input string as the second argument to the isValidFormat method. The method returns a boolean value indicating whether the input string matches the specified format.

Sample 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

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