# Reverse an Integer in Java

Sheeraz Gul Mar 09, 2022

This tutorial will demonstrate how to reverse an integer in Java without using an array.

When reversing an integer without using the array, there are three steps we need to follow.

## Use Recursion to Reverse an Integer in Java

Recursion is the simplest method to reverse an integer with modulo and division operators.

Example:

``````import java.util.Scanner;
public class Reverse_Recursion{
//Create a method to reverse a number using recursion
public static void Recursion_reverse(int input_number){
if (input_number < 10){
//If the number is less then 10 then no need to reverse
System.out.println(input_number);
return;
}
else{
System.out.print(input_number % 10);
Recursion_reverse(input_number/10);
}
}
public static void main(String args[]){
System.out.print("Enter the Integer you want to Reverse: ");
Scanner input_num = new Scanner(System.in);
int input_number = input_num.nextInt();
System.out.print("The reverse of the given number using recursion is: ");
Recursion_reverse(input_number);
}
}
``````

Output:

``````Enter the Integer you want to Reverse: 1234567890
The reverse of the given number using recursion is: 0987654321
``````

## Use the `while` Loop to Reverse an Integer in Java

To reverse an integer using a `while` loop, we must follow all three steps mentioned.

Example:

``````import java.util.Scanner;
public class Reverse_While{
public static void main(String args[]){
System.out.print("Enter the Integer you want to Reverse: ");
Scanner input_num = new Scanner(System.in);
int input_number = input_num.nextInt();
int reverse_number = 0;
while(input_number != 0){
int remainder_number = input_number % 10;
reverse_number = reverse_number * 10 + remainder_number;
input_number = input_number/10;
}
System.out.println("The reverse of the given number using while loop is: " + reverse_number);
}
}
``````

Output:

``````Enter the Integer you want to Reverse: 123456789
The reverse of the given number using while loop is: 987654321
``````

## Use the `for` Loop to Reverse an Integer in Java

The `for` loop also works similar to the `while` loop reverses an integer.

Let’s try to reverse a negative integer this time.

Example:

``````import java.util.Scanner;
public class Reverse_For{
public static void main(String args[])  {
System.out.print("Enter the Integer you want to Reverse: ");
Scanner input_num = new Scanner(System.in);
int input_number = input_num.nextInt();
int reverse_number = 0;
for( ;input_number != 0; input_number=input_number/10){
int remainder_number = input_number % 10;
reverse_number = reverse_number * 10 + remainder_number;
}
System.out.println("The reverse of the given number using while loop is: " + reverse_number);
}
}
``````
``````Enter the Integer you want to Reverse: -123456789
The reverse of the given number using while loop is: -987654321
``````
Author: Sheeraz Gul

Sheeraz is a Doctorate fellow in Computer Science at Northwestern Polytechnical University, Xian, China. He has 7 years of Software Development experience in AI, Web, Database, and Desktop technologies. He writes tutorials in Java, PHP, Python, GoLang, R, etc., to help beginners learn the field of Computer Science.