Iterative Constructs in Java

Chapter 9

Iterative Constructs in Java

Class 10 - Logix Kips ICSE Computer Applications with BlueJ

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Java Program: Reverse the Digits of a Number

16. Write a program in Java to read a number and display its digits in the reverse order. For example, if the input number is 2468, then the output should be 8642.

Output:
Enter a number: 2468
Original number: 2468
Reverse number: 8642

import java.util.Scanner;
 
public class ReverseNumber {
    public static void main(String[] args) {
 
        Scanner sc = new Scanner(System.in);
 
        System.out.print("Enter a number: ");
        int num = sc.nextInt();
 
        int original = num;
        int reverse = 0;
 
        while (num != 0) {
            int digit = num % 10;
            reverse = reverse * 10 + digit;
            num = num / 10;
        }
 
        System.out.println("Original number: " + original);
        System.out.println("Reverse number: " + reverse);
    }
}
 

Sample Output
Enter a number: 2468
Original number: 2468
Reverse number: 8642 

📝 Explanation

• % 10 extracts the last digit
• reverse = reverse * 10 + digit builds the reversed number
• / 10 removes the last digit
• Loop continues until the number becomes 0