Java Newton Method

Implementation of Newton Method written in Java.

IN
-3
0.0000001
OUT
X: -3.0 f(x): 2.0
X: -2.5 f(x): 0.25
X: -2.4166666666666665 f(x): 0.006944444444443976
X: -2.4142156862745097 f(x): 6.007304882427178E-6

import java.util.Scanner;

// ? 2018 TheFlyingKeyboard and released under MIT License
// theflyingkeyboard.net
public class Main {
    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
        double prevX;
        double x;
        double precision;

        System.out.print("Enter initial guess: ");
        x = reader.nextDouble();

        prevX = x;

        System.out.print("Enter precision of method: ");
        precision = reader.nextDouble();

        while(Math.abs(function(x)) > precision){
            System.out.println("X: " + x + " f(x): " + function(x));

            x = prevX - (function(prevX) / functionDerivative(prevX));
            prevX = x;
        }
    }

    private static double function(double x) { //x^2 + 2x - 1
        return x * (x + 2) - 1;
    }

    private static double functionDerivative(double x) { //x^2 + 2x - 1
        return 2 * x + 2;
    }
}