Print Reverse number in java program -

import java.util.Scanner;
class ReverseNumber {
  public static void main(String args[]) {
    int n, reverse = 0;

    System.out.println("Enter the number to reverse");
    Scanner in = new Scanner(System.in);
    n = in.nextInt();
    while (n != 0) {
      reverse = reverse * 10;
      reverse = reverse + n % 10;
      n = n / 10;
    }
    System.out.println("Reverse of entered number is " + reverse);
  }
}

Step-by-Step Explanation:

1. Import the Scanner Class:

import java.util.Scanner;

The Scanner class is imported to read input from the user.

2. Class Declaration:

class ReverseNumber {

This declares a class named ReverseNumber that contains the main method, which will execute the logic.

3. Main Method Declaration:

public static void main(String args[]) {

The main method is the entry point for the Java program. It is where execution begins.

4. Declare Variables:

int n, reverse = 0;

n: This integer variable will hold the number entered by the user.
reverse: This variable will store the reversed number, initialized to 0.

5. Prompt for User Input:

System.out.println(“Enter the number to reverse”);

The program asks the user to input a number that he wants to reverse.

6. Create Scanner Object and Read Input:

Scanner in = new Scanner(System.in);

n = in.nextInt();

A scanner object named in it is made to read the input from the user.

A call to nextInt() method reads an integer from the user, which is stored in the variable n.

7. Reversing the Number Using While Loop:

while (n != 0)

{

reverse = reverse * 10; // Shift the current reverse number to the left

reverse = reverse + n % 10; // Add the last digit of n to reverse

n = n / 10; // Remove the last digit from n

}

The while loop continues as long as n is not zero. The loop performs the following steps on each iteration:

1. Shift the Current Reverse:

reverse = reverse * 10: Shift the existing digits of reverse to the left by multiplying it by 10 (or add a new digit at the unit place).

2. Extract the Last Digit of n:

reverse = reverse + n % 10: Here, the last digit of n is appended to reverse. The expression n % 10 extracts the last digit of n.

3. Remove the Last Digit from n :

n = n / 10: This deletes the last digit of n by dividing it by 10. This truncates the decimal part, effectively shifting all digits to the right.

These steps repeat until all digits of n are processed.

8. Print the Reversed Number:

System.out.println(“Reverse of entered number is ” + reverse);

After the while loop terminates, the program outputs the reversed number stored in the reverse

What Occurs When the Program Is Executed?

It prompts the user to input a number.
It reverses the digits of the number through the while loop.
It extracts the rightmost side digit, concatenating them in the reverse variable till n is reduced to 0.

Sample Output:

#Sample 1:

Input:

Enter the number to reverse

12345

Implementation:

In the first iteration:

reverse = 0 * 10 + 12345 % 10 = 0 + 5 = 5
n = 12345 / 10 = 1234

In the second iteration:

reverse = 5 * 10 + 1234 % 10 = 50 + 4 = 54
n = 1234 / 10 = 123

In the third iteration:

reverse = 54 * 10 + 123 % 10 = 540 + 3 = 543
n = 123 / 10 = 12

In the fourth iteration:

reverse = 543 * 10 + 12 % 10 = 5430 + 2 = 5432
n = 12 / 10 = 1

In the fifth iteration:

reverse = 5432 * 10 + 1 % 10 = 54320 + 1 = 54321
n = 1 / 10 = 0

After these operations, n is 0, and the program prints “Reverse of entered number is 54321”

Output:

Reverse of entered number is 54321

#Example 2: Input a Single Digit