Java For Loop into Recursive function

Question

public class For {
 public static void main(String[] args){
          for(int i=2; i<=1024; i *= 2){
           System.out.println("Count is: " + i);
      }
 }




public class While {
    public static void main(String[] args){
        int i = 1;
        while (i < 1024) {
            i *= 2;
            System.out.println("Count is: " + i);
      }
 }


public class DoWhile {
     public static void main(String[] args){
        int i = 1;
        if (i < 1024) {
            do { i*=2;
                System.out.println("Count is: " + i);
            } while (i < 1024);
        }
     }

How would one convert the for loop/while loop so it does the same thing, but using a recursive function?

Solution 1

Like so:

public class Recursive {
    public void r(int i) {
        if (i < 1024) {
            i *= 2;
            System.out.println("Count is: " + i);
            r(i);
        }
    }

    public static void main(String[] args) {
        Recursive r = new Recursive();
        r.r(1);
    }
}

Solution 2

Take the loop of main and put it in its own function with an argument int i. In that function, rewrite the loop to

1. If the loop condition is false (i >= 1024), then return
2. Else, recursive call with argument i*2.

Call the function with argument 1 or 2, depending on which of your programs you're rewriting (they don't entirely match).

Solution 3

Recurrent loop can look like this:

class Main
{
    public static void main(String[] args){
      RecWhile(1);
    }

    public static void RecWhile(int i) {
       if (i < 1024) {
         i = i*2;
         System.out.println("Count is: " + i);
         RecWhile(i);
       }
    }
}

Comments

[Ingo]

-1 for being not helpful. Enabling students to solve the problem at hand is helpful, to serve them the solution on a silver tray is not, IMHO. Why should Manpreet Pangli ever care listeing to his professor, when it's so cheap to get the answer from SO?

[Lukasz]

It produces different results than the examples in OPs question. Your program starts printing from 1. Multiplication by 2 should be done before println.

[Lukasz]

@Ingo: I didn't know it's homework. There's no homework tag. I think it's not fair to -1 answers not because they are not correct, but they were given to "homework questions".

[David Grant]

@Ingo: it's hard to argue against your point, although it is a little judgemental!

[Lukasz]

This answer is marked -1 not because it's incorrect, but BECAUSE it was given to a question that was not supposed to be answered this way (of course, that's not my POV; but the that's the way it is on Stack Overflow)

[Ingo]

No, that's me, not SO. If you do not see that this can only be homework, I can't help it.

[Ingo]

Yes, @David, I care about the next generation programmers, even if they're from India. And I can't stand it if people can get away with avoidance of thinking.