使用方法求解二次方程，java

Question

我有一个为求解二次方程而编写的 Java 程序，但作业要求我为每项任务提供方法：显示方程、确定方程是否有实解、计算解以及显示解（如果有）存在。除了检查解决方案是否真实之外，我对所有事情都有方法，除了我的方法说它们是未定义的。有人可以帮我格式化我的方法吗，我不太知道如何实现它们？这是我到目前为止的代码：

import java.util.Scanner;
public class QuadraticFormula {

public static void main(String[] args)
{
    //Creating scanner and variables
    Scanner s = new Scanner(System.in);
    System.out.println("Insert value for a: ");
    double a = Double.parseDouble(s.nextLine());
    System.out.println("Insert value for b: ");
    double b = Double.parseDouble(s.nextLine());
    System.out.println("Insert value for c: ");
    double c = Double.parseDouble(s.nextLine());

    //Display format for negatives
    displayEquation(double a, double b, double c);{
    if (b > 0 && c > 0 ){
        System.out.println(a + "x^2 + " + b + "x + " + c + " =0");}
    if (b < 0 && c > 0 ){
        System.out.println(a + "x^2 " + b + "x + " + c + " =0");}
    if (b > 0 && c < 0 ){
        System.out.println(a + "x^2 + " + b + "x " + c + " =0");}
    if (b < 0 && c < 0 ){
        System.out.println(a + "x^2 " + b + "x " + c + " =0");}
    s.close();
    }
    //The work/formula
    private static double calculateSolution(double a, double b, double c); 
    {
    double answer1 = (-b + Math.sqrt(Math.pow(b, 2) - (4 * a * c))) / (2 * a);
    return answer1;
    }

    private static double calculateSolution(double a, double b, double c); 
    {
    double answer2 = (-b - Math.sqrt(Math.pow(b, 2) - (4 * a * c))) / (2 * a);
    return answer2;
    }
    //Display results and check if the solution is imaginary (real or not)
    private static void displaySolutions(double answer1, double answer2); {
    if (Double.isNaN(answer1) || Double.isNaN(answer2))
    {
        System.out.println("Answer contains imaginary numbers");
    } else System.out.println("The values are: " + answer1 + ", " + answer2);
}
}

}

Answer 1

您的方法需要在您的主要方法之外定义。然后你可以像这样在你的 main 方法中调用它们：

displayEquation(a, b, c);

您还应该删除方法定义后的分号。它应该是这样的：

public class QuadraticFormula {

public static void main(String[] args)
{
    //Creating scanner and variables
    Scanner s = new Scanner(System.in);
    System.out.println("Insert value for a: ");
    double a = Double.parseDouble(s.nextLine());
    System.out.println("Insert value for b: ");
    double b = Double.parseDouble(s.nextLine());
    System.out.println("Insert value for c: ");
    double c = Double.parseDouble(s.nextLine());
    s.close();
}
    //Display format for negatives
    public static void displayEquation(double a, double b, double c) {
        if (b > 0 && c > 0 ){
            System.out.println(a + "x^2 + " + b + "x + " + c + " =0");}
        if (b < 0 && c > 0 ){
            System.out.println(a + "x^2 " + b + "x + " + c + " =0");}
        if (b > 0 && c < 0 ){
            System.out.println(a + "x^2 + " + b + "x " + c + " =0");}
        if (b < 0 && c < 0 ){
            System.out.println(a + "x^2 " + b + "x " + c + " =0");}
    }

    private static double calculateSolution(double a, double b, double c) {
        double answer2 = (-b - Math.sqrt(Math.pow(b, 2) - (4 * a * c))) / (2 * a);
        return answer2;
    }

    //Display results and check if the solution is imaginary (real or not)
    private static void displaySolutions(double answer1, double answer2) {
        if (Double.isNaN(answer1) || Double.isNaN(answer2))
        {
            System.out.println("Answer contains imaginary numbers");
        }   
        else System.out.println("The values are: " + answer1 + ", " + answer2);
    }
}