How to reverse a number in Java

In previous post How to swap or exchange two numbers with or without using any temporary variable in java we learnt how to swap two number with or without using any temporary variable.

In this post we will learn How to reverse a number in Java

package com.kkjavatutorials.client;

import java.util.Scanner;
/**
 * @author KK JavaTutorials
 * This Java program is all about How to reverse a number without using recursion
 */
public class ClientTest1 {

	public static void main(String[] args) {

		try (Scanner scanner = new Scanner(System.in)) {
			//Take a number from keyboard using Scanner
			System.out.println("Enter Number:");
			int number = scanner.nextInt();
			
			System.out.println("Original number:"+number);
			
			int reversedNumber = reverseNumber(number);
			System.out.println("Reversed Number:"+reversedNumber);
			
		} catch (Exception e) {
			System.out.println("Please Enter valid number..");
			e.printStackTrace();
		}
	}

	private static int reverseNumber(int number) {
		//Logic to reverse a number
		int reversedNumber = 0;
		int mode = 0;
		while (number != 0) {
			mode = number % 10;
			reversedNumber = (reversedNumber * 10) + mode;
			number = number / 10;
		  }
		return reversedNumber;
	}
}

package com.kkjavatutorials.client;

import java.util.Scanner;

/**

* @author KK JavaTutorials

* This Java program is all about How to reverse a number without using recursion

public class ClientTest1 {

public static void main(String[] args) {

try (Scanner scanner = new Scanner(System.in)) {

//Take a number from keyboard using Scanner

System.out.println("Enter Number:");

int number = scanner.nextInt();

System.out.println("Original number:"+number);

int reversedNumber = reverseNumber(number);

System.out.println("Reversed Number:"+reversedNumber);

} catch (Exception e) {

System.out.println("Please Enter valid number..");

e.printStackTrace();

}

private static int reverseNumber(int number) {

//Logic to reverse a number

int reversedNumber = 0;

int mode = 0;

while (number != 0) {

mode = number % 10;

reversedNumber = (reversedNumber * 10) + mode;

number = number / 10;

}

return reversedNumber;

}

I have tested above program for few inputs as below. You may check for other input as well

Enter Number:
8971
Original number:8971
Reversed Number:1798

Enter Number:
-186
Original number:-186
Reversed Number:-681

Enter Number:
00188
Original number:188
Reversed Number:881

Enter Number:

8971

Original number:8971

Reversed Number:1798

Enter Number:

-186

Original number:-186

Reversed Number:-681

Enter Number:

00188

Original number:188

Reversed Number:881

That’s all about this topic How to reverse a number in Java

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