Write a Java program to check whether an given integer is power of 2 or not using O(1) time

import java.util.*;
public class Main 
 {
 public static void main(String[] args)
  {
      boolean b = true;
      Scanner in = new Scanner(System.in);
      System.out.print("Input a number : ");
      int num = in.nextInt();           
     {   
     while(num!=1)
      {
        if(num%2!=0)
          { 
            b=! b;
            System.out.print(b);
            System.exit(0);
          }
            num = num / 2;
      }
       System.out.print(b);
     }
  }
         
}

Sample Output:

Input a number :  25
false