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Leap Year Program in Java (Check Leap Year or Not)

Understanding and dealing with dates and calendars is a fundamental skill in programming. One common challenge is finding whether a given year is a leap year or not. Leap years play a crucial role in our calendars by adding an extra day, February 29th, every four years. This seemingly simple adjustment is essential for keeping our calendars in sync with the Earth's orbit around the sun.

Here, we will learn about the concept of leap years, explore the rules, and write a Java program to check given year is a leap year or not. 

What Are Leap Years?

A leap year, also known as an intercalary year, is a year that contains an extra day, February 29th, bringing the total number of days in the year to 366 instead of the usual 365. 

This extra day is added to keep our calendar year synchronized with the Earth's orbit, which takes approximately 365.2422 days to complete. By adding an extra day every four years, we maintain this synchronization more accurately.

Use Cases of Java Leap Year Program

  • Date and Time Calculations: Leap year calculations are essential in many date and time-related applications, such as scheduling, event planning, and financial calculations.

  • Software Development: Leap year logic is often needed in software applications that deal with date and time, like calendars, scheduling software, and countdown timers.

  • Financial and Accounting Systems: Leap year calculations can be crucial for interest rate calculations, amortization schedules, and other financial calculations that involve dates.

  • Data Analysis: In data analysis and reporting, identifying leap years can be important when analyzing trends and patterns over time.

  • Algorithm Design: Leap year checks can be a part of more complex algorithms where accurate date calculations are required.

Now that we understand the significance of leap years and their applications, let's dive into the Java programming language to create a leap year checker program. Let's get started!

Concepts to Learn:

Leap Year Program in Java Using if else

Here's a program for leap year in Java using conditional statements (if-else):

Code

import java.util.Scanner;

public class LeapYearChecker {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a year: ");
        int year = scanner.nextInt();

        if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) {
            System.out.println(year + " is a leap year.");
        } else {
            System.out.println(year + " is not a leap year.");
        }

        scanner.close();
    }
}

Output

Enter a year: 2020
2020 is a leap year.

Explanation

  • We import the java.util.Scanner class to read input from the user.

  • We prompt the user to enter a year using System.out.print("Enter a year: ") and then read the input into the year variable.

We use the following conditions to check for a leap year:

  • If the year is divisible by 4 (year % 4 == 0) and not divisible by 100 (year % 100 != 0), or

  • If the year is divisible by 400 (year % 400 == 0), then we consider it a leap year. Otherwise, it's not a leap year.

Depending on the result of the conditions, we output whether the year is a leap year or not.

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Program for Leap Year in Java Using Calendar Class

Here's a leap year program in Java using the Calendar class:

Code

import java.util.Calendar;
import java.util.Scanner;

public class LeapYearChecker {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a year: ");
        int year = scanner.nextInt();
        
        Calendar calendar = Calendar.getInstance();
        calendar.set(Calendar.YEAR, year);
        
        if (calendar.getActualMaximum(Calendar.DAY_OF_YEAR) > 365) {
            System.out.println(year + " is a leap year.");
        } else {
            System.out.println(year + " is not a leap year.");
        }

        scanner.close();
    }
}

Output

Enter a year: 2024
2024 is a leap year.

Explanation

  • We import the java.util.Calendar class to work with dates and calendars, and we also import java.util.Scanner for user input.

  • We prompt the user to enter a year using System.out.print("Enter a year: ") and then read the input into the year variable.

  • We create an instance of the Calendar class using Calendar.getInstance().

  • We set the year of the Calendar object to the user-inputted year using calendar.set(Calendar.YEAR, year).

  • We use calendar.getActualMaximum(Calendar.DAY_OF_YEAR) to get the actual maximum number of days in the given year. If this number is greater than 365, it indicates a leap year.

Check Leap Year or Not in Java Using java.time API

Here's a leap year program in Java using the java.time API:

Code

import java.time.Year;
import java.util.Scanner;

public class LeapYearChecker {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a year: ");
        int year = scanner.nextInt();
        
        Year y = Year.of(year);
        
        if (y.isLeap()) {
            System.out.println(year + " is a leap year.");
        } else {
            System.out.println(year + " is not a leap year.");
        }

        scanner.close();
    }
}

Output

Enter a year: 2025
2025 is not a leap year.

Explanation

  • We import the java.time.Year class to work with years and dates, and we also import java.util.Scanner for user input.

  • We prompt the user to enter a year using System.out.print("Enter a year: ") and then read the input into the year variable.

  • We create a Year object by calling Year.of(year) to represent the inputted year.

  • We use the isLeap() method of the Year object to check if it's a leap year.

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