/**
 * @author: Joshua Gibbs
 * @title: ICA Ch. 11-1a
 * @date: 2/22/2017
 * @file: ICA11_1a.java
 * @class: CS 141 – Programming and Problem Solving
 * @purpose:
 * Write a program that has the following subroutine:
 *
 *  static double root(double A, double B, double C)
 *                               throws IllegalArgumentException {
 *    // Returns the larger of the two roots of
 *    // the quadratic equation A*x*x + B*x + C = 0.
 *    // (Throws an exception if A == 0 or B*B-4*A*C < 0.)
 *    if (A == 0) {
 *      throw new IllegalArgumentException("A can't be zero.");
 *    }
 *    else {
 *      double disc = B*B - 4*A*C;
 *      if (disc < 0)
 *        throw new IllegalArgumentException("Discriminant < zero.");
 *      return  (-B + Math.sqrt(disc)) / (2*A);
 *    }
 *  }
 *
 * From within your main method for your program you should ask the user for three values.
 * Then you should call up our subroutine root and pass in the values given.
 * You should use a try catch block to handle any exceptions.
 * If a solution can be calculated for the three values, print out that solution.
 * If an exception is encountered, print out an error message.
*/

import java.util.Scanner;

public class ICA11_1a {
    public static void main (String[] args) {
        System.out.print("Please enter three space-separated numbers: ");
        Scanner in = new Scanner(System.in);
        double a = Double.parseDouble(in.next());
        double b = Double.parseDouble(in.next());
        double c = Double.parseDouble(in.next());
        try {
            System.out.println("Solution = " + root(a, b, c));
        } catch (IllegalArgumentException error) {
            System.out.println(error);
        }
    }

    static double root(double a, double b, double c) throws IllegalArgumentException {
        // Returns the larger of the two roots of
        // the quadratic equation a*x*x + b*x + c = 0.
        // (Throws an exception if a == 0 or b*b-4*a*c < 0.)
        if (a == 0) {
            throw new IllegalArgumentException("a can't be zero.");
        } else {
            double disc = b * b - 4 * a * c;
            if (disc < 0) {
                throw new IllegalArgumentException("Discriminant < zero.");
            }
            return  (-b + Math.sqrt(disc)) / (2 * a);
         }
     }
}