java用mvc写一个一元二次方程， 要有测试类，并给代码标准一下

好的，以下是一个使用MVC模式实现一元二次方程的Java代码：

Model层：Equation.java

public class Equation {
    private double a;
    private double b;
    private double c;
    private double delta;
    private double x1;
    private double x2;
    
    public void setCoefficient(double a, double b, double c) {
        this.a = a;
        this.b = b;
        this.c = c;
        calculateDelta();
        calculateRoots();
    }
    
    private void calculateDelta() {
        delta = b * b - 4 * a * c;
    }
    
    private void calculateRoots() {
        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 getDelta() {
        return delta;
    }
    
    public double getX1() {
        return x1;
    }
    
    public double getX2() {
        return x2;
    }
}

View层：EquationView.java

import java.util.Scanner;

public class EquationView {
    private Scanner scanner;

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

    public void displayResult(double delta, double x1, double x2) { 
        if (Double.isNaN(x1) && Double.isNaN(x2)) {
            System.out.println("该方程无实数解！");
        } else if (delta == 0) {
            System.out.println("该方程有唯一解：x=" + x1);
        } else {
            System.out.println("该方程有两个解：x1=" + x1 + "，x2=" + x2);
        }
    }
    
    public double[] getCoefficient() {
        double[] coefficient = new double[3];
        System.out.println("请依次输入一元二次方程的系数：");
        coefficient[0] = scanner.nextDouble();
        coefficient[1] = scanner.nextDouble();
        coefficient[2] = scanner.nextDouble();
        return coefficient;
    }
}

Controller层：EquationController.java

public class EquationController {
    private EquationView view;
    private Equation model;
    
    public EquationController(EquationView view, Equation model) {
        this.view = view;
        this.model = model;
    }
    
    public void processEquation() {
        double[] coefficient = view.getCoefficient();
        model.setCoefficient(coefficient[0], coefficient[1], coefficient[2]);
        view.displayResult(model.getDelta(), model.getX1(), model.getX2());
    }
}

测试类：EquationTest.java

public class EquationTest {
    public static void main(String[] args) {
        EquationView view = new EquationView();
        Equation model = new Equation();
        EquationController controller = new EquationController(view, model);
        controller.processEquation();
    }
}

代码规范：

1. 类名采用大驼峰命名法，即每个单词首字母大写，比如EquationView、EquationController等；
2. 方法名采用小驼峰命名法，即第一个单词首字母小写，后面的单词首字母大写，比如setCoefficient、calculateDelta等；
3. 变量名采用小驼峰命名法，比如a、b、c、delta、x1、x2等；
4. 类、方法、变量等的命名要具有描述性，能够清晰表达其意义；
5. 代码中要有适当的注释，能够帮助他人理解代码的功能。