Java Program to Reverse a Number

Last Updated: 17 August, 2022

On this tutorial page we are going to learn how to write a Java program to reverse a number. For example, if we input a number 246810 then will get 018642 as a reverse number.

In the given program we are reversing a number using for loop and while loop. Let's see the implementation.

Program 1: Reverse a number using while loop in Java

  public class ReverseNumber {
    public static void main(String[] args) {
      
      int number = 12345;
      int reversed_number = 0;
  
      System.out.println("The Original Number: " + number);
      
      while (number != 0) {
  
        // Getting the last digit from the number
        int digit = number % 10;
        reversed_number = reversed_number * 10 + digit;
  
        // Removing the last digit from the number
        number = number / 10;
      }
      
      System.out.println("The Reversed Number: " + reversed_number);
    }
  }

Output

The Original Number: 12345
The Reversed Number: 54321

Program 2: Reverse a number using for loop in Java

  public class ReverseNumber2 {
    public static void main(String[] args) {
  
      int number = 12345;
      int reversed_number = 0;
  
      System.out.println("The Original Number: " + number);
  
      for (; number != 0; number = number / 10) {
        int digit = number % 10;
        reversed_number = reversed_number * 10 + digit;
      }
  
      System.out.println("The Reversed Number: " + reversed_number);
    }
  }

Output

The Original Number: 12345
The Reversed Number: 54321

Program 3: Reverse a number using for loop and user input in Java

  
  import java.util.Scanner;
  public class ReverseNumber3 {
    public static void main(String[] args) {
      
      Scanner scanner = new Scanner(System.in);
      System.out.print("Enter the number: ");
      long number = scanner.nextLong();
      scanner.close();
      long reversed_number = 0;
      
      for (; number != 0; number = number / 10) {
        long digit = number % 10;
        reversed_number = reversed_number * 10 + digit;
      }
      
      System.out.println("The Reversed Number: " + reversed_number);
    }
  }

Output

Enter the number: 987654321
The Reversed Number: 123456789