Java Program to Print Even Numbers from 1 to n

You can print even numbers from 1 to n in Java using a for loop and checking if a number is divisible by 2 with if (i % 2 == 0), then printing it.

Examples

Input5

Output2 4

Input10

Output2 4 6 8 10

Input1

Output

How to Think About It

To print even numbers from 1 to n, start from 1 and go up to n. For each number, check if it divides evenly by 2 using the remainder operator %. If the remainder is zero, it means the number is even, so print it.

Algorithm

1

Get input number n from the user

2

Start a loop from 1 to n

3

For each number i, check if i % 2 equals 0

4

If yes, print the number i

5

Continue until the loop ends

Code

java

import java.util.Scanner;

public class EvenNumbers {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        for (int i = 1; i <= n; i++) {
            if (i % 2 == 0) {
                System.out.print(i + " ");
            }
        }
        scanner.close();
    }
}

Output

2 4 6 8 10 

Dry Run

Let's trace input n=5 through the code

1

Input

User enters n = 5

2

Loop start

i = 1, check if 1 % 2 == 0 (false), do not print

3

Loop continues

i = 2, check if 2 % 2 == 0 (true), print 2

4

Next iterations

i = 3 (false), i = 4 (true, print 4), i = 5 (false)

5

Loop ends

Printed numbers: 2 4

i	i % 2 == 0?	Printed
1	false
2	true	2
3	false
4	true	4
5	false

Why This Works

Step 1: Loop through numbers

The for loop goes from 1 to n, checking each number one by one.

Step 2: Check even condition

Using i % 2 == 0 checks if the number divides evenly by 2, meaning it is even.

Step 3: Print even numbers

If the number is even, it is printed followed by a space to separate numbers.

Alternative Approaches

Start loop from 2 and increment by 2

java

import java.util.Scanner;

public class EvenNumbers {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        for (int i = 2; i <= n; i += 2) {
            System.out.print(i + " ");
        }
        scanner.close();
    }
}

This method skips checking odd numbers by starting at 2 and jumping by 2, making it more efficient.

Use while loop with condition

java

import java.util.Scanner;

public class EvenNumbers {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int i = 2;
        while (i <= n) {
            System.out.print(i + " ");
            i += 2;
        }
        scanner.close();
    }
}

Using a while loop with increments of 2 also prints even numbers efficiently.

Complexity: O(n) time, O(1) space

Time Complexity

The program loops from 1 to n once, so it runs in linear time O(n).

Space Complexity

It uses only a few variables and prints output directly, so space is constant O(1).

Which Approach is Fastest?

Starting the loop at 2 and incrementing by 2 is faster because it skips odd numbers and reduces the number of iterations by half.

Approach	Time	Space	Best For
Check each number with if	O(n)	O(1)	Simple and clear logic
Loop from 2, increment by 2	O(n/2)	O(1)	More efficient, fewer checks
While loop increment by 2	O(n/2)	O(1)	Alternative loop style, efficient