How to Sanity Check a Date in Java

Sanity checking a date in Java is an important aspect of software development to ensure the correctness and reliability of the application.

It helps to validate the input data and prevent unexpected behavior and errors in the application.

In this tutorial, we will learn how to perform a sanity check on a date in Java and validate it in a concise and efficient way.

Introduction

Dates are an integral part of any software application, whether it’s a web application, mobile app, or desktop software.

They are used to store and retrieve the date and time information, calculate the difference between two dates, and perform various other operations.

However, the date input from the user can be unpredictable and may contain invalid data, which can lead to errors in the application.

That’s why it’s crucial to perform a sanity check on a date in Java to ensure its validity before using it in the application.

Validate Date Format

The first step in validating a date in Java is to check its format. Java supports several date and time formats, and it’s important to ensure that the date entered by the user conforms to a specific format.

The simplest way to validate the date format is to use the SimpleDateFormat class in Java.

It provides the parse method that throws a ParseException if the date format is invalid.

Here’s an example code that validates a date in the format “yyyy-MM-dd”:

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

public class DateSanityCheck {

    public static void main(String[] args) {
        String dateString = "2023-02-07";
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");

        try {
            Date date = dateFormat.parse(dateString);
            System.out.println("Valid date format");
        } catch (ParseException e) {
            System.out.println("Invalid date format");
        }
    }
}

Check for Leap Year

The next step in validating a date in Java is to check for a leap year.

A leap year is a year that has one extra day (February 29) compared to a regular year.

The logic for checking a leap year is simple, and it involves dividing the year by 4, 100, and 400.

If the year is divisible by 4, it’s a leap year, but if it’s divisible by 100, it’s not a leap year, except if it’s also divisible by 400, then it’s a leap year.

Here’s an example code that checks for a leap year:

public class DateSanityCheck {

    public static void main(String[] args) {
        int year = 2022;

        boolean isLeapYear = false;

        if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) {
            isLeapYear = true;
        }

        System.out.println("Is Leap Year: " + isLeapYear);
    }
}

Check for Valid Day and Month

The final step in validating a date in Java is to check for a valid day and month.

This involves checking that the day of the month is within the correct range for the corresponding month and year.

For example, the month of February can have 28 or 29 days, depending on whether it’s a regular year or a leap year.

Here’s an example code that checks for a valid day and month:

public class DateSanityCheck {

    public static void main(String[] args) {
        int year = 2022;
        int month = 2;
        int day = 29;

        boolean isValidDate = true;

        switch (month) {
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                if (day < 1 || day > 31) {
                    isValidDate = false;
                }
                break;
            case 4:
            case 6:
            case 9:
            case 11:
                if (day < 1 || day > 30) {
                    isValidDate = false;
                }
                break;
            case 2:
                if (((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0)) {
                    if (day < 1 || day > 29) {
                        isValidDate = false;
                    }
                } else {
                    if (day < 1 || day > 28) {
                        isValidDate = false;
                    }
                }
                break;
            default:
                isValidDate = false;
        }

        System.out.println("Is Valid Date: " + isValidDate);
    }
}