Happy Number In Java

import java.util.Scanner;
   class HappyNumber{
  public static void main(String[] args) {
    int num;
    int mul;
    int sum = 0;
   Scanner sc = new Scanner(System.in);
   System.out.println("Enter a number");
        num = sc.nextInt();
      while(sum!=1&&sum!=4){
        sum = 0;

        while(num>0){

          mul = num%10;
          sum = (mul*mul);
          num = num/10;

        }
            num = sum;

         if(sum==1){
          System.out.println("Happy Number");
         }   
         else{
          System.out.println("UnHappy Number");
             }
          }
        }
    }