How to understand the work of while in a for loop?

Question

Java

class help {
  public static void main (String args[]) {
  int e;
  int result;

    for (int i=0;i < 10; i++) {
      result = 1;
      e = i;
          
      while(e > 0) {
        result *= 2;
        e--;
      }
      System.out.println("2 в степени " + i + " равно " + result);
      
    }
      
  }
  
}

There is such a code, I understand that in the For loop we get numbers from 1 to 9, and go to the while loop,
but here I have questions, I don’t understand if we declared result = 1; , then in the loop we get result = result * 2; , that is, result = 1*2 , there is no increment on it, that is, in theory, it is result = 1; should always be the same as 2... but then how did it all work out?
Please help me figure it out..

Answer 1

1. The for loop iterates over the numbers 0, 1, 2 ... 9
2. Inside the loop, at the beginning, result = 1, and e = i
3. Before each iteration of the while loop, a comparison with zero occurs
4. Inside the iteration, we multiply result by 2
5. At the end of the iteration, we subtract e.
Here, the only thing that matters to us is that the multiplication of result by 2 will be repeated i times,
the while loop can be rewritten here as follows:

class help {
  public static void main (String args[]) {    
    for (var i=0;i < 10; i++) {
      var result = 1;
      for(var j = 0; j < i; j++)
        result *= 2;
      System.out.println("2 в степени " + i + " равно " + result);  
    }
  }
}