Java How To Reverse a Number

Reverse a Number

Take an integer and print it in reverse order:

Example

int num = 1234;
int reversed = 0;

while (num != 0) {
  int digit = num % 10;
  reversed = reversed * 10 + digit;
  num /= 10;
}

System.out.println("Reversed: " + reversed);

Explanation: We start with the number 1234. Inside the loop:

• num % 10 gives us the last digit (4, then 3, then 2, then 1).
• We add this digit to reversed, making the new number grow step by step.
• num /= 10 removes the last digit from the original number.

When the loop finishes, reversed contains 4321.