How to check whether given date is valid or not in Java?

Problem Description :

Write a program in Java that checks whether given date is valid or not.

Date Validation in Java

Concept :

A date is valid if it satisfies following constraints.

1.  It should be in correct format. For example - dd/MM/yyyy.
2.  It exist in reality. For example - 30/02/2015 is not exist so it is invalid.

For validating first constraint we are using Regular expressions and for second constraint setLenient() method of DateFormat class.

Few points to note down about setLenient() method.

• By default setLenient() is true. Means, it won't check whether date exist in reality or not.
• To make it eligible for validating real dates we have to turn it off.

Java Program :

	package com.javamultiplex.datetime;
	import java.text.DateFormat;
	import java.text.ParseException;
	import java.text.SimpleDateFormat;
	import java.util.Scanner;
	/**
	*
	* @author Rohit Agarwal
	* @category Date and Time
	* @problem Check whether date is valid or not?
	*
	*/
	public class DateValid {
	/*
	* Date is valid if It's format is correct (For ex : dd/MM/yyyy) It exist in
	* reality, I mean 30/02/2016 is in correct format but there is not such
	* date in reality, So invalid.
	*/
	public static void main(String[] args) {
	Scanner input = null;
	try {
	input = new Scanner(System.in);
	System.out.println("Enter date in dd/MM/yyyy format : ");
	String date = input.next();
	if (isDateValid(date)) {
	System.out.println("Date is valid.");
	} else {
	System.out.println("Date is not valid.");
	}
	} finally {
	if (input != null) {
	input.close();
	}
	}
	}
	private static boolean isDateValid(String date) {
	boolean result = false;
	if (isValidDateFormat(date)) {
	/*
	* d -> Day of month
	* M -> Month of year
	* y -> Year
	*/
	DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
	/*
	* By default setLenient() is true. We should make it false for
	* strict date validations.
	*
	* If setLenient() is true - It accepts all dates. If setLenient()
	* is false - It accepts only valid dates.
	*/
	dateFormat.setLenient(false);
	try {
	dateFormat.parse(date);
	result = true;
	} catch (ParseException e) {
	result = false;
	}
	}
	return result;
	}
	private static boolean isValidDateFormat(String date) {
	/*
	* Regular Expression that matches String with format dd/MM/yyyy.
	* dd -> 01-31
	* MM -> 01-12
	* yyyy -> 4 digit number
	*/
	String pattern = "(0?[1-9]|[12][0-9]|3[01])\\/(0?[1-9]|1[0-2])\\/([0-9]{4})";
	boolean result = false;
	if (date.matches(pattern)) {
	result = true;
	}
	return result;
	}
	}

view raw DateValid.java hosted with ❤ by GitHub

Output :

Case 1 :

Output - Date is valid

Case 2 :

Output - Date not exist

Case 3 :

Output - Date is not valid

References :

https://en.wikipedia.org/wiki/Regular_expression

http://docs.oracle.com/javase/7/docs/api/java/lang/String.html

https://docs.oracle.com/javase/7/docs/api/java/util/Date.html

http://docs.oracle.com/javase/7/docs/api/java/text/DateFormat.html#setLenient(boolean)

https://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html

Thank you friends, I hope you have clearly understood the solution of this problem. If you have any doubt, suggestion or query please feel free to comment below. You can also discuss this solution in our forum.

Tags : Date and Time Problems, Date validation in Java, SimpleDateFormat, Regular expressions, if else statement, String, DateFormat.

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