Java用Mvc写一个一元二次方程

好的，以下是一个简单的Java MVC模式实现的一元二次方程计算器：

Model（模型）：

public class QuadraticEquation {
    private double a;
    private double b;
    private double c;
    private double x1;
    private double x2;

    public QuadraticEquation(double a, double b, double c) {
        this.a = a;
        this.b = b;
        this.c = c;
    }

    public void solve() {
        double delta = b * b - 4 * a * c;
        if (delta < 0) {
            x1 = Double.NaN;
            x2 = Double.NaN;
        } else {
            x1 = (-b + Math.sqrt(delta)) / (2 * a);
            x2 = (-b - Math.sqrt(delta)) / (2 * a);
        }
    }

    public double getX1() {
        return x1;
    }

    public double getX2() {
        return x2;
    }
}

View（视图）：

public class QuadraticEquationView {
    private Scanner scanner;

    public QuadraticEquationView() {
        scanner = new Scanner(System.in);
    }

    public double getA() {
        System.out.print("Enter a: ");
        return scanner.nextDouble();
    }

    public double getB() {
        System.out.print("Enter b: ");
        return scanner.nextDouble();
    }

    public double getC() {
        System.out.print("Enter c: ");
        return scanner.nextDouble();
    }

    public void displayResult(double x1, double x2) {
        if (Double.isNaN(x1) || Double.isNaN(x2)) {
            System.out.println("No real roots");
        } else if (x1 == x2) {
            System.out.println("The only root is " + x1);
        } else {
            System.out.println("The two roots are " + x1 + " and " + x2);
        }
    }
}

Controller（控制器）：

public class QuadraticEquationController {
    private QuadraticEquation model;
    private QuadraticEquationView view;

    public QuadraticEquationController(QuadraticEquation model, QuadraticEquationView view) {
        this.model = model;
        this.view = view;
    }

    public void run() {
        double a = view.getA();
        double b = view.getB();
        double c = view.getC();

        model = new QuadraticEquation(a, b, c);
        model.solve();

        double x1 = model.getX1();
        double x2 = model.getX2();

        view.displayResult(x1, x2);
    }
}

Main（主程序）：

public class Main {
    public static void main(String[] args) {
        QuadraticEquation model = new QuadraticEquation(0, 0, 0);
        QuadraticEquationView view = new QuadraticEquationView();
        QuadraticEquationController controller = new QuadraticEquationController(model, view);

        controller.run();
    }
}

在控制台里运行Main类，按照提示输入三个参数a、b和c，程序将会计算出一元二次方程的两个根并输出。