Reverse an Integer Number in Java

In one of the previous posts, you saw how we can reverse a String in Java. Today, we will cover a case when we need to reverse a number.

To reverse a number in Java, we can apply the same logic as we did in Check if a number is a palindrome question earlier.

Solution:

public class DevPrimer {

  public static void main(String[] args) {
    System.out.println(reverseNumber(123));
  }

  private static int reverseNumber(int number) {
    int reverse = 0;

    while (number > 0) {
      int reminder = number % 10;
      reverse = (reverse * 10) + reminder;
      number = number / 10;
    }

    return reverse;
  }
}

Output: 321

Here, we first get a reminder of a given number using modulo (%) and add it to the reverse value.
Note: we need to multiply the reverse with 10, if we don't - we'll get for example(2 + 3 = 5), and we actually need (23, so (2 * 10) + 3 = 23).
After that, we remove the last digit, since it is a reminder that we already added to the reverse value.

That is how we can reverse an Integer Number in Java.