Quadratic Equation Calculator

quadratic_polynomial.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class CodingGame {

    private static int getValueOfCoefficient(String value) {
        if (value != null) {
            if (value.isEmpty()) {
                return 1;
            } else if (value.equals("-")) {
                return -1;
            } else {
                return Integer.parseInt(value);
            }
        }

        return 0;
    }

    public static void main(String[] args) {
        String function = "x²-x+1";
        int x = 2;

        Pattern quadrupole = Pattern.compile("((?<xpow>-?\\d*)x²)?((?<x>[+-]\\d*)x)?(?<cnst>[+-]?\\d+)");
        Matcher matcher = quadrupole.matcher(function);
        if (matcher.matches()) {
            int xpow = getValueOfCoefficient(matcher.group("xpow"));
            int xValue = getValueOfCoefficient(matcher.group("x"));
            int cnst = getValueOfCoefficient(matcher.group("cnst"));

            System.out.println("x²: " + matcher.group("xpow"));
            System.out.println("x: " + matcher.group("x"));
            System.out.println("constant: " + matcher.group("cnst"));

            int result = (xpow * x * x) + (xValue * x) + cnst;
            System.out.println("Result: " + result);
        }
    }
}