Java Program to Reverse a Number by Using Recursion

Java Program to Reverse a Number by Using Recursion

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In the previous article, we have discussed about Java Program to Find Nth Power of a Number by Using Recursion

In this program we are going to see how to reverse a number using recursion by Java programming language.

Java Program to Reverse a Number by Using Recursion

Let’s see an example to understand it more clearly.

Assume a number n = 94371
Then the reverse of the number = 17349

Now let’s see different ways to reverse a number by using Recursion.

Method-1: Java Program to Reverse a Number By Using Static Input and Recursion

Approach:

  • Declare an integer variable ‘n’ and initialize it.
  • Call a user defined method reverseNumber() method and pass the Integer ‘n’ as parameter.
  • Inside the user defined method we will check if the the number is 1 digit number then print the same number ‘n’.
  • Else if the number is greater than 1 digit then recursively call reverseNumber() method to extract the digits and print it.

Program:

public class Main 
{
    public static void main(String[] args)
    {
        //declare an integer variable ‘n’ and initialize it
        int n = 94371;
        System.out.println("The reverse of the number "+n+" is:");
        //calling reverseNumber() method to reverse the number
        reverseNumber(n);
    }

    //recursive function to reverse a number        
    static void reverseNumber(int n)
    {
        // if the number is 1 digit number then print the same number
        if(n<10)
        System.out.print(n);
        // if the number is more than 1 digit number then recursively call reverseNumber() method and print the remainder
        else
        {
    	    System.out.print(n%10);
            reverseNumber(n/10);
        } 
    }
}

Output:

The reverse of the number 94371 is:
17349

Method-2: Java Program to Reverse a Number By Using User Input and Recursion

Approach:

  • Create a scanner class.
  • Declare an integer variables say ‘n’
  • Prompt the user to enter the values for the integer.
  • Declare an integer variable ‘n’ and initialize it.
  • Call a user defined method reverseNumber() method and pass the integer ‘n’ as parameter.
  • Inside the user defined method we will check if the the number is 1 digit number then print the same number ‘n’.
  • Else if the number is greater than 1 digit then recursively call reverseNumber() method to extract the digits and print it.

Program:

import java.util.*;
import java.io.*;
public class Main 
{
    public static void main(String[] args)
    {
        // create a scanner class
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter a number: ");
        //declare an integer variable ‘n’and initialize it by user input using scanner class.
        int n = sc.nextInt();
        System.out.println("The reverse of the number "+n+" is:");
        //calling reverseNumber() method to reverse the number
    	reverseNumber(n);
    }

    //recursive function to reverse a number        
    static void reverseNumber(int n)
    {
        // if the number is 1 digit number then print the same number
        if(n<10)
        System.out.print(n);
        // if the number is more than 1digit number then recursively call reverseNumber() method and print the remainder
        else
        {
            System.out.print(n%10);
            reverseNumber(n/10);
        } 
    }
}

Output:

Enter a number: 
73810
The reverse of the number 73810 is:
01837

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