GA.2

/******************************
 * @file GA2Math.java
 * Answers for GA.2
 * @author hypesystem
 */

package ga2math;

/**
 * This is a class to handle math. Specifically math from GA.2.
 * Basically it uses the main class to run the GA2Math class to run the Quadratic class.
 * This is to keep the Quadratic class as clean as possible, and make the application
 * executable. True story.
 * @author hypesystem
 */
public class GA2Math {

    private Quadratic doMath;
    private Quadratic doMath2;
    private Quadratic doMath3;

    /**
     * Creates objects of the Quadratic-class and does stuff with them!
     */
    public GA2Math() {
        doMath = new Quadratic(3,9,-30);
        doMath.show();
        System.out.println("x = 3; y = " + doMath.compute(3));
        doMath.solve();
        System.out.println("");
        doMath2 = new Quadratic(-3,1,-1);
        doMath2.show();
        System.out.println("x = 3; y = " + doMath2.compute(3));
        doMath2.solve();
        System.out.println("");
        doMath3 = new Quadratic(10,3,-5);
        doMath3.show();
        System.out.println("x = 4; y = " + doMath3.compute(4));
        doMath3.solve();
    }

    /**
     * Instantiates the application.
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        GA2Math doTheMath = new GA2Math();
    }
}

/******************************
 * @file Quadratic.java
 * Answers for GA.2
 * @author hypesystem
 */

package ga2math;

import java.text.*;

/**
 * This class holds a quadratic that can be solved, shown and calculated for a
 * specific value of x.
 * @author hypesystem
 */
public class Quadratic {

    private double a;
    private double b;
    private double c;
    private NumberFormat nf = NumberFormat.getInstance();

    /**
     * Creates a Quadratic of the format ax^2+bx+c with the given values.
     * @param a
     * @param b
     * @param c
     */
    public Quadratic(double a, double b, double c) {
        this.a = a;
        this.b = b;
        this.c = c;
        nf.setMaximumFractionDigits(2);
    }

    /**
     * Inputs the values of a, b and c into the format of a quadratic,
     * checks whether a > 0 (if it is a quadratic, or a linear function,
     * then prints.
     */
    public void show() {
        String print = "";
        if(a != 0) {
            print = "Andengradspolynomie:\n";
        }
        else {
            print = "Lineær funktion:\n";
        }
        print = print + nf.format(a) + "x^2";
        if(b >= 0) {
            print = print + "+";
        }
        print = print + nf.format(b) + "x";
        if(c >= 0) {
            print = print + "+";
        }
        print = print + nf.format(c);
        System.out.println(print);
    }

    /**
     * Calculates quadratic with given value of x
     * @param x
     * @return formatted number with max. 2 decimals as String
     */
    public String compute(double x) {
        return nf.format((a * x * x) + (b * x) + c);
    }

    /**
     * Solves the quadratic by finding all solutions, if any. If it is
     * a linear function, it is solved as such.
     * Note: solve, superSolve & robustSolve combined.
     */
    public void solve() {
        String print = "";
        if(a != 0) {
            double d = (b * b) - (4 * a * c);
            if(d < 0) {
                print = "Ingen løsninger.";
            }
            else if(d == 0) {
                double solve = (0 - b + Math.sqrt(d)) / (2 * a);
                print = "Én løsning: " + solve;
            }
            else if(d > 0) {
                double solve1 = (0 - b + Math.sqrt(d)) / (2 * a);
                double solve2 = (0 - b - Math.sqrt(d)) / (2 * a);
                print = "To løsninger: " + nf.format(solve1) + " og " + nf.format(solve2);
            }
        }
        else if (b != 0) {
            double solve = (0 - c / b);
            print = "Løsning: " + nf.format(solve);
        }
        else {
            if(c == 0) {
                print = "Løsning: alle x";
            }
            else {
                print = "Ingen løsninger";
            }
        }
        System.out.println(print);
    }

}