Класс для решения квадратных уравнений

EquationSolver.java

package xyz.nuark;

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

/**
 * @author Nuark
 * @version 1.0
 * 
 * Класс, который решает квадратные уравнения.
 * Уравнения должны поступать в формате "ax^2 + bx + c = 0"(можно и без пробелов).
 * Аргументы a, b и c не должны выходить за рамки double 
 * double - 64-разрядное число в формате IEEE 754 с плавающей точкой [-1.7E+308 .. 1.7E+308]
 */
public class EquationSolver {
	public String equation;
	private double a, b, c;
	private final String regex = "([+-]?\\d+|[+-])?x\\^2[\\s]([+-][\\s]?\\d+|[+-])?x[\\s]+([+-]\\s?\\d+)[\\s]=[\\s]([+-]?\\d+)";
	private Pattern pattern;
	private Matcher matcher;

	public EquationSolver(String equation) throws Exception {
		equation = formatString(equation);
		if (checkEquation(equation)){
			if (!equation.contains("x^2") || !equation.contains("x"))
				throw new Exception("Quadratic equation expected, linear given");
			this.equation = equation;
			splitToPieces();
		} else throw new Exception("Not an equation");
	}
	
	private boolean checkEquation(String equation){
		pattern = Pattern.compile(regex);
		matcher = pattern.matcher(equation);
		return matcher.find();
	}
	
	private String formatString(String equation){
		return equation.replace(" ", "").replace("-0", "0").replace("=", " = ").replace("+", " +").replace("-", " -").trim();
	}
	
	private void splitToPieces(){
		String eq = this.equation;
		String[] tmp = eq.split(" = ");
		int exc = Integer.parseInt(tmp[1]);
		String[] t = tmp[0].split(" ");
		String _a = t[0].replace("x^2", "");
		String _b = t[1].replace("x", "");
		String _c = t[2];
		if ((_a.length() == 1) && ("-".equals(_a) || "+".equals(_a))) _a = _a.concat("1");
		else if (_a.length() == 0) _a = _a.concat("1");
		if ((_b.length() == 1) && ("-".equals(_b) || "+".equals(_b))) _b = _b.concat("1");
		else if (_b.length() == 0) _b = _b.concat("1");
		if ((_c.length() == 1 || _c.length() == 0) && ("-".equals(_c) || "+".equals(_c))) _c = _c.concat("1");
		else if (_c.length() == 0) _c = _c.concat("1");
		a = Double.parseDouble(_a);
		b = Double.parseDouble(_b);
		c = Double.parseDouble(_c) + exc;
	}
	
	public double[] solveEquation() throws Exception{
		double _a = this.a;
		double _b = this.b;
		double _c = this.c;
		double discr = (_b * _b) - (4 * _a * _c);
		if (discr > 0){    
			double sq_discr = Math.sqrt(discr);
			double x1 = (_b * -1) + sq_discr / (2 * _a);
			double x2 = (_b * -1) - sq_discr / (2 * _a);
			return new double[]{x1, x2};
		} else if (discr == 0) {
			double x1 = (_b * -1) / (2 * _a);
			return new double[]{x1};
		} else {
			throw new Exception("Complex number can not be expressed with double type");
		}
	}
}

Main.java

package xyz.nuark;

public class Main {

	public static void main(String[] args) {
		String test = "4x2-4x-42=0\n" +
				"-1x^2 -2x +4 = 0\n" +
				"x^2 +0x -16 = 0\n" +
				"-x^2 +0x -16 = 0\n" +
				"x^2 +x -16 = 0\n" +
				"-x^2 +x -16 = 0\n" +
				"x^2 -x -16 = 0\n" +
				"-x^2 -x -16 = 0\n" +
				"4x^2 +0x -16 = 0\n" +
				"-0x^2 -25x +4225 = 0\n" +
				"9x^2 - 30 = 0\n" +
				"8x^2 + 45454541x - 42 = 0\n" +
				"3x^2 - 0x - 27 = 0\n" +
				"1x^2 - 0x - 16 = 0\n" +
				"25x + 50 = 0\n" +
				"123154549480 + 4\n" +
				"-25x - 50 = 0\n" +
				"1x^2 - 25x - 0 = 9\n" +
				"2x^2 - 0x - 8 = 5\n" +
				"1x^2 -0x - 16 = 0\n" +
				"3x^2 - 0x - 27 = 0\n" +
				"9x^2 - 3x + 0 = 0\n" +
				"3x^2 - 0x - 257 = 0\n" +
				"1313215645564x^2 + 6546x - 45451212115484 = 0\n" +
				"9х = 4545454\n" +
				"0\n" +
				"3x^2 - 0x + 27 = 0\n" +
				"2x^2 -1x + 28 = 0\n" +
				"1x^2 - 2x + 29 = 0\n" +
				"8x^2 a 2x + 29 = 0\n" +
				"1x^2 - 2x 1 29 = 0\n" +
				"1x^2 - 2x ++ 29 = 0\n" +
				"-2x . 29 = 0\n" +
				"-2x + 29 = 0\n" +
				"фx^2 -1x + a8 = 0";
		for (String eq : test.split("\n")){
			try {
				EquationSolver su = new EquationSolver(eq);
				double[] answers = su.solveEquation();
				if (answers.length == 1)
					System.out.println("Equation " + eq + " has one answer: " + answers[0]);
				else 
					System.out.println("Equation " + eq + " has two answers: " + answers[0] + " and " + answers[1]);
			} catch (NumberFormatException ex) {
				System.out.println("Wow, how? " + ex + " :: " + eq);
			} catch (Exception ex) {
				System.out.println(ex + " :: " + eq);
			}
		}
	}
}