# Java Program to Reverse a Number

Reading Time: 7 minutes

## Introduction:

This Java program is designed to reverse the digits of a given integer. It prompts the user to input a number, then uses a simple algorithm to reverse the digits of that number and finally displays the reversed result.

### Algorithm:

1. Input: The program starts by using the Scanner class to take an integer input from the user.
2. Reversing Algorithm: The reverseNumber method is called, which takes the input number as a parameter and uses a while loop to reverse its digits.
• Inside the loop, the last digit of the number is obtained using the modulus operator (%).
• The reversedNumber is updated by multiplying it by 10 and adding the extracted digit.
• The last digit is removed from the original number by dividing it by 10.
• This process continues until the original number becomes zero.
3. Output: The reversed number is then printed to the console.

### Explanation:

• The Scanner class is used to get user input for the number to be reversed.
• The reverseNumber method encapsulates the logic for reversing the digits.
• A while loop is employed to extract the digits one by one from the original number and build the reversed number.
• The result is then printed to the console using System.out.println.

This program is a basic example of how to reverse the digits of a number in Java, demonstrating the use of loops, arithmetic operations, and method calls.

### Code :

```    ```
import java.util.Scanner;
public class ReverseNumber {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a number: ");
int number = scanner.nextInt();
int reversedNumber = reverseNumber(number);
System.out.println("Reversed number: " + reversedNumber);
scanner.close();
}
private static int reverseNumber(int number) {
int reversedNumber = 0;
while (number != 0) {
int digit = number % 10;
reversedNumber = reversedNumber * 10 + digit;
number /= 10;
}
return reversedNumber;
}
}

```
```

### Input :

```    ```
Enter a number: 65
```
```

### Output :

```    ```
Reversed number: 56
```
```

This program takes an integer input from the user, reverses the digits, and then prints the reversed number.

### FAQ’s :

How can I write a Java program to reverse a number?

• You can easily reverse a number in Java by using a simple program. One way is to convert the number to a string, reverse the string, and then convert it back to an integer. Another method involves using mathematical operations to reverse the digits. Would you like a code example for either approach?

What is the simplest Java program to reverse a number?

• A straightforward Java program to reverse a number typically involves converting it to a string, reversing the string, and converting it back to an integer. This approach is beginner-friendly and easy to understand. Would you like to see the code for this method?

Can you provide a Java program to reverse a number without using a string?

• Certainly! You can reverse a number in Java without converting it to a string by using mathematical operations. This involves extracting digits one by one and forming the reversed number. Would you like a code snippet for this approach?

Are there different ways to reverse a number in Java?

• Yes, there are multiple ways to reverse a number in Java. One common method involves string manipulation, while another approach utilizes mathematical operations to reverse the digits directly. Depending on your preference or specific requirements, you can choose the method that suits your needs. Would you like more details or examples?

What are the considerations when writing a Java program to reverse a large number?

• When dealing with large numbers in Java, it’s essential to consider potential overflow issues and the efficiency of the chosen algorithm. Depending on the size of the number, a more optimized approach may be necessary to ensure performance. Would you like guidance on handling large numbers in your reverse program?