No error! Can't find the solution with java.lang.StackOverflowError

Question

import java.util.*;

public class NRootx {

    public static Double NRmethod (Double num, int root, Double guess){
        guess= num/(root+1); //first guess  

        Double guess_output=1.0;

        for (int i=1;i<=root; i++)
        {
            guess_output *= guess;
        }

        Double error= guess_output-num;
        error = error * 0.001;
        guess = guess - error;

        if (Math.abs(error)>=0.000001)
            return NRmethod(num, root, guess); //Recursion 
        else
            return guess;

           //I can't find out the problem now. Java.lang.StackOverFlow error is showing. 

        }
    }
}

// Main function 
public static void main(String[] args) {

    Double x;
    int n;
    Scanner sc= new Scanner (System.in);
    System.out.println("Enter the value of x: ");
    x=sc.nextDouble();
    System.out.println("Enter the value of n: ");
    n=sc.nextInt();
    Double guess=x/(n+1);
    Double ans= NRmethod(x,n,guess);
    System.out.println("The value of y is ="+ans);
}

Please someone help me to solve this. I am being tired of doing this for many time.

Answer 1

I got my answer myself. Asking for a guess will solve the problem. Do not need to set the guess like the code I have given. However, I do not know the reason but it solved the problem. Thank you.

Answer 2

You never change root and num, and you reset guess in each call to guess= num/(root+1);, so you get an endless recursion, leading to StackOverflowError.

I'm not sure what the correct logic should be, but to prevent the endless recursion you must either pass different values of root or num to each recursive call, or don't reset guess at the start of the method.