CODEWITHSUNDEEP
javaloopssquare-root
Dem
Dem

Reputation: 61

Finding square roots using approximations and loop

this program is supposed to take a non negative integer and find the square root
The square root of a non-negative number n can be calculated successive approximations. At each step, a new approximation is calculated as follows:

next approximation = (n / current + current) / 2

The process of approximation continues until the value is close enough, that is, the difference between (current * current) and n is small enough to be acceptable. However when i go print my answer nothing comes up. what am i doing wrong. is my loop not working correctly?

import java.io.*;
import java.util.*;
import java.lang.*;
import java.text.*;

public class Squareroot1 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter a non negative integer: ");
        double n = in.nextInt();
        double result = approx(n);
        /*double current = result;
            while ((current * current)- n == Math.sqrt(n)) {
                double nextapproximation = (n/current + current)/2;
                nextapproximation = current;
                System.out.println(nextapproximation);
        }*/

        System.out.println( result);
    }

    public static double approx(double val) {
        double current = val;
        double approximation = (val / current + current) / 2;
        return approximation;
    }
}

Upvotes: 1

Views: 1225

Answers (1)

Michael Markidis
Michael Markidis

Reputation: 4191

You have a few issues:

1) Your while loop condition should be:

while ((current * current) - n != 0)

2) You are not setting current to the value of the nextapproximation

3) You are not printing out the final result (which should be current).

The code:

double result = aprox(n);
double current = result;
while ((current * current) - n != 0)
{
    double nextapproximation = (n / current + current) / 2;

    // Stop infinite loop
    if (nextapproximation == current)
    {
        break;
    }
    current = nextapproximation;
    System.out.println(current);
}
System.out.println("Result: " + current);

Test Run:

Enter a non negitive integer: 23
6.958333333333333
5.131861277445109
4.806832989404423
4.795844112917605
4.795831523329245
4.795831523312719
Result: 4.795831523312719

EDIT:

You don't need the aprox method and you don't need the result variable.

Before the while loop simply do:

double n = in.nextInt();
double current = (n / n + n) / 2;

Upvotes: 1

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