(Algebra: solve quadratic equations) Write a method for solving a quadratic equation using the following header:

package Chapter_07;

import java.util.Scanner;

/**
 * Chapter 7 Exercise 25:
 *
 *      (Algebra: solve quadratic equations)
 *      Write a method for solving a quadratic equation using the following header:
 *
 *              public static int solveQuadratic(double[] eqn, double[] roots)
 *
 *      The coefficients of a quadratic equation ax2 + bx + c = 0 are passed to the
 *      array eqn and the real roots are stored in roots. The method returns the number
 *      of real roots. See Programming Exercise 3.1 on how to solve a quadratic equation.
 *      Write a program that prompts the user to enter values for a, b, and c and displays
 *      the number of real roots and all real roots.
 *
 * Created by Luiz Arantes Sa on 8/28/14.
 */
public class Exercise_25 {

    public static void main(String[] args) {

        double[] eqn = new double[3];
        double[] roots = new double[3];
        Scanner input = new Scanner(System.in);
        System.out.print("Enter a, b, c: ");
        for (int i = 0; i < eqn.length; i++) eqn[i] = input.nextDouble();

        int rootNum = solveQuadratic(eqn, roots);

        if (rootNum == 0) System.out.print("No real roots.\n");
        else printRoots(roots, rootNum);



    }

    private static void printRoots(double[] roots, int numberOfRoots) {
        for (int i = 0; i < numberOfRoots; i++) {
            System.out.println("Root " + (i + 1) + " = " + roots[i]);
        }
    }

    public static int solveQuadratic(double[] eqn, double[] roots) {

        double a = eqn[0];
        double b = eqn[1];
        double c = eqn[2];
        double discriminant = b * b - 4.0 * a * c;

        if (discriminant > 0.0) {
            roots[0] = (-b + Math.pow(discriminant, 0.5)) / (2.0 * a);
            roots[1] = (-b - Math.pow(discriminant, 0.5)) / (2.0 * a);
            return 2;
        } else if (discriminant == 0.0) {
            roots[0] = -b / (2.0 * a);
            return 1;
        }

        return 0;
    }
}