Java用Mvc写一个一元二次方程

好的，以下是使用Java MVC模式设计的一元二次方程计算器：

Model（模型）：Equation.java

public class Equation {
    private double a, b, c;
    private double discriminant;
    private double root1, root2;

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

    public void solve() {
        discriminant = b * b - 4 * a * c;

        if (discriminant < 0) {
            root1 = Double.NaN;
            root2 = Double.NaN;
        } else if (discriminant == 0) {
            root1 = -b / (2 * a);
            root2 = root1;
        } else {
            root1 = (-b + Math.sqrt(discriminant)) / (2 * a);
            root2 = (-b - Math.sqrt(discriminant)) / (2 * a);
        }
    }

    public double getRoot1() {
        return root1;
    }

    public double getRoot2() {
        return root2;
    }
}

View（视图）：EquationView.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionListener;

public class EquationView extends JFrame {
    private JTextField aField = new JTextField(5);
    private JTextField bField = new JTextField(5);
    private JTextField cField = new JTextField(5);
    private JTextField root1Field = new JTextField(10);
    private JTextField root2Field = new JTextField(10);

    private JButton solveButton = new JButton("Solve");

    public EquationView() {
        JPanel equationPanel = new JPanel(new GridLayout(2, 3));
        equationPanel.add(new JLabel("a:"));
        equationPanel.add(aField);
        equationPanel.add(new JLabel("x^2 +"));
        equationPanel.add(new JLabel("b:"));
        equationPanel.add(bField);
        equationPanel.add(new JLabel("x +"));
        equationPanel.add(new JLabel("c:"));
        equationPanel.add(cField);
        equationPanel.add(new JLabel("="));

        JPanel rootPanel = new JPanel(new GridLayout(2, 2));
        rootPanel.add(new JLabel("Root 1:"));
        rootPanel.add(root1Field);
        rootPanel.add(new JLabel("Root 2:"));
        rootPanel.add(root2Field);

        JPanel buttonPanel = new JPanel(new FlowLayout());
        buttonPanel.add(solveButton);

        JPanel mainPanel = new JPanel(new BorderLayout());
        mainPanel.add(equationPanel, BorderLayout.CENTER);
        mainPanel.add(rootPanel, BorderLayout.SOUTH);
        mainPanel.add(buttonPanel, BorderLayout.EAST);

        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setTitle("Quadratic Equation Solver");
        this.setSize(400, 150);
        this.setLocationRelativeTo(null);
        this.setResizable(false);
        this.add(mainPanel);
    }

    public double getA() {
        return Double.parseDouble(aField.getText());
    }

    public double getB() {
        return Double.parseDouble(bField.getText());
    }

    public double getC() {
        return Double.parseDouble(cField.getText());
    }

    public void setRoot1(double root1) {
        root1Field.setText(Double.toString(root1));
    }

    public void setRoot2(double root2) {
        root2Field.setText(Double.toString(root2));
    }

    public void addSolveListener(ActionListener listener) {
        solveButton.addActionListener(listener);
    }
}

Controller（控制器）：EquationController.java

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class EquationController {
    private EquationView view;
    private Equation model;

    public EquationController(EquationView view, Equation model) {
        this.view = view;
        this.model = model;

        view.addSolveListener(new SolveListener());
    }

    class SolveListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            double a = view.getA();
            double b = view.getB();
            double c = view.getC();

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

            view.setRoot1(model.getRoot1());
            view.setRoot2(model.getRoot2());
        }
    }
}

Main（主函数）：Main.java

public class Main {
    public static void main(String[] args) {
        Equation model = new Equation(1, 1, -6);
        EquationView view = new EquationView();
        EquationController controller = new EquationController(view, model);

        view.setVisible(true);
    }
}

在运行程序时，将显示一个窗口，用户可以输入一元二次方程的系数，并点击“Solve”按钮计算方程的根。计算结果将显示在窗口下方的文本框中。

注意：为了使代码更简洁，此处省略了一些异常处理和输入验证等细节。在实际开发中，应该对用户输入进行验证，以确保程序的正确性和健壮性。