Why is my Variable set to 0?

Question

import java.lang.Math;
public class NewtonIteration {

    public static void main(String[] args) {
     System.out.print(rootNofX(2,9));
    }

    // computes x^n
    public static double power(double x, int n) {
     if (n==0) {
      return 1;
     }  
     double Ergebnis = 1;
     for (int i=0; i<=Math.abs(n)-1; i++) {
      Ergebnis *= x;
     }
     if (n<0) {
      Ergebnis = 1/Ergebnis;
     }

     return Ergebnis;
    }

    // computes x^(1/n)
    public static double rootNofX(int n, double x) {
     return power(x, 1/n);
    }
}

Whenever power(x,1/n) is called, n is reset to 0. But isn't n a parameter given to rootNofX with the value 2?

Answer 1

It's because you're using integers, so 1 / 2 = 0.5 which as an integer is 0. Change the prototypes to rootNofx(double n, double x) and power(double x, double n).

Also, since rootNofx uses power, in my opinion, it would be better to have the parameters ordered the same way, to avoid confusion.

Answer 2

1/n is going to be a fraction, usually, but in the declaration of power you declare n to be integer. That's going to knock off the decimal places every time!

Answer 3

It's because power is defined with "n" as an int so 1/n will always be less than 1 which will be zero when stored as an int. Update "int n" to "double n". Example below:

public static double power(double x, double n) { ... }

Answer 4

Try:

// computes x^(1/n)
    public static double rootNofX(int n, double x) {
        return power(x, 1.0/n);
    }

Because 1 is an int and n is an int so 1/n is an integer division which return 0 when n is not 1 and throw error when n is 0.

1.0 is a double so it make 1.0/n a double division that you want.

Answer 5

The problem is that you are passing 1/2 from rootNofX into an int, so it becomes zero.

Answer 6

There is a big difference between 1/n and 1.0/n

Consider what declaring n to be an int really means...