Java program to check if a year is a leap year or not

Java program to check if a year is a leap year or not:

In this Java programming tutorial, we will learn how to check if a year is leap year or not. This program will take one number as the input and print a message that it is leap year or it is not.

A year is a leap year if it is divisible by 4 and for century years, it is also divisible by 400. So, we need to check if the year is divisible by 4 and for century years, it is divisible by 400 or not.

Let’s understand the algorithm before start writing the program.

Algorithm to use:

We will use the below algorithm:

  • Take the year as input from the user.
  • Check if the number is divisible by 4 or not. If not, then return false or it is not a leap year.
  • If it is divisible by 4, we need to check if it is a century year or not. If it is divisible by 100, it is a century year.

    • If it is not a century year, it is a leap year.
    • If it is a century year, check if it is divisible by 400 or not. If yes, it is a leap year. Else, it is not.

Following years are leap year: 1904, 1908, 1912, 1916, 1920, 1924, 1928, 1932, 1936, 1940, 1944, 1948, 1952, 1956, 1960, 1964, 1968, 1972, 1976, 1980, 1984, 1988, 1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020.

Let’s write it in code:

Java program to check if a year is leap year or not:

Below program checks if a year is leap year or not:

import java.util.Scanner;

class Main {

    public static boolean isLeapYear(int year) {
        if (year % 4 == 0) {
            if (year % 100 == 0) {
                return year % 400 == 0;
            } else {
                return true;
            }
        }

        return false;
    }

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

        Scanner sc = new Scanner(System.in);
        System.out.println("Enter the number: ");
        year = sc.nextInt();

        if (isLeapYear(year)) {
            System.out.println(year + " is a leap year");
        } else {
            System.out.println(year + " is not a leap year");
        }

    }
}

Here,

  • isLeapYear method is used to check if a year is leap year or not. It takes the year as the parameter and returns one boolean value.
  • The first if block checks if the value is divisible by 4 or not. If yes, it checks if it is divisible by 100 or not. If yes, it checks if it is divisible by 400. If not, it returns true.
  • It returns false if the year value is not divisible by 4.

If you run this program, it will print output as like below:

Enter the number: 
1988
1988 is a leap year

Enter the number: 
1989
1989 is not a leap year

We can use a loop and use the method used in the above program to find out all leap years in a specific range. For example:

class Main {

    public static boolean isLeapYear(int year) {
        if (year % 4 == 0) {
            if (year % 100 == 0) {
                return year % 400 == 0;
            } else {
                return true;
            }
        }

        return false;
    }

    public static void main(String[] args) {
        for (int i = 1900; i < 2021; i++) {
            if (isLeapYear(i)) {
                System.out.println(i);
            }
        }

    }
}

In this program, the for loop runs from 1900 to 2020 and it will print all leap years in between these two years.

1904
1908
1912
1916
1920
1924
1928
1932
1936
1940
1944
1948
1952
1956
1960
1964
1968
1972
1976
1980
1984
1988
1992
1996
2000
2004
2008
2012
2016
2020

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