Java program to reverse a number

In this post, you will learn different Java programs to reverse a number. Such a type of question can improve your logical problem solving skill.

Java program to reverse a number using for loop

In the given Java program, we ask the user to enter an integer number and use the for loop to reverse the entered number.

class ReverseNumber {
  public static void main(String[] args) {
    
    int num = 89764532, rev_num = 0;
    System.out.println("Original Number: " + num);
    for(;num != 0; num /= 10) {
      int digit = num % 10;
      rev_num = rev_num * 10 + digit;
    }
    System.out.println("Reversed Number: " + rev_num);
  }
}

Output of the above code:

Original Number: 89764532
Reversed Number: 23546798

Java program to reverse a number using while loop

In the given Java program, we take the input number from the user using the Scanner class and then reverse the number using while loop.

import java.util.Scanner;

public class ReverseNumberProgram   
{  
    public static void main(String[] args)   
    {  
    // taking user input   
    Scanner sc=new Scanner(System.in);
    System.out.println("Enter a number : ");
    int num =sc.nextInt();
    int rev = 0;  
    
    while(num != 0)   
    {  
    int remainder = num % 10;  
    rev = rev * 10 + remainder;  
    num = num/10;  
    }  
    System.out.println("Reverse of the given number : " + rev); 
    }  
} 

Output of the above code:

Enter a number : 349871
Reverse of the given number : 178943

Java program to reverse a number using recursion

Recursion function is a function which is call itself. In the given example, we call the recursion function to get the reverse of a number. A recursion function continues until some condition is met to prevent it. That's why, we use the if statement to break the infinite recursion. In the given Java program, we have used recursion to reverse a given number -

import java.util.Scanner;  
public class ReverseNumber 
{  
    //method for reverse a number  
    public static void reverseNumber(int num)   
    {  
        if(num < 10)   
        {  
            System.out.println(num);  
            return;  
        }  
        else   
        {  
            System.out.print(num % 10);  
            reverseNumber(num/10);  
        }  
    }  
    public static void main(String args[])  
    {  
        System.out.print("Enter a number: ");  
        Scanner sc = new Scanner(System.in);  
        int num = sc.nextInt();  
        System.out.print("Reverse of the given number: ");  
        reverseNumber(num);  
    }  
}  

Output of the above code:

Enter a number: 7865432
Reverse of the given number: 2345687

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