Java reverse int value

Question

Can anyone explain to me how to reverse an integer without using array or String. I got this code from online, but not really understand why + input % 10 and divide again.

while (input != 0) {
    reversedNum = reversedNum * 10 + input % 10;
    input = input / 10;   
}

Answer 1

I am not clear about your Odd number. The way this code works is (it is not a Java specific algorithm) Eg. input =2345 first time in the while loop rev=5 input=234 second time rev=5*10+4=54 input=23 third time rev=54*10+3 input=2 fourth time rev=543*10+2 input=0

So the reversed number is 5432. If you just want only the odd numbers in the reversed number then. The code is

while (input != 0)
{    
     last_digit = input % 10;
     if(last_digit % 2 != 0)
     {     
            reversedNum = reversedNum * 10 + last_digit;

     }
      input = input / 10; 
}

Answer 2

public int reverseNumber(int number)
{
  int reversedNumber = 0;
  while(number != 0)
  {
     reversedNumber = (reversedNumber * 10) + (number % 10);
     number /= 10;
  }
  return reversedNumber;
}