java - 获得二次方程的准确根

Question

这是我迄今为止所拥有的代码。该项目的目标是让用户输入 a 的任意整数。 , b , c对于ax^2+bx+c方程。由于某种原因，我没有获得输入到程序中的任何数字的正确根。谁能指出我的错误行为吗？

import java.util.*;


public class Quad_Form {

public static void main(String[] args){

    Scanner sc = new Scanner(System.in);

    double a = 0;
    double b = 0;
    double c = 0;
    double discrim = 0;
    double d = 0;

    System.out.println("Enter value for 'a'");
    String str_a = sc.nextLine();
    a = Integer.parseInt(str_a);

    System.out.println("Enter value for 'b'");
    String str_b = sc.nextLine();
    b = Integer.parseInt(str_b);

    System.out.println("Enter value for 'c'");
    String str_c = sc.nextLine();
    c = Integer.parseInt(str_c);

    double x1 = 0, x2 = 0;
    discrim = (Math.pow(b, 2.0)) - (4 * a * c);
    d = Math.sqrt(discrim);

    if(discrim == 0){
        x1 = (-b + d) / (2* a);
        String root_1 = Double.toString(x1);
        System.out.println("There is one root at: " + root_1);
        }

    else {
        if (discrim > 0)
        x1 = (-b + d) / (2 * a);
        x2 = (-b - d) / (2 * a);
        String root_1 = Double.toString(x1);
        String root_2 = Double.toString(x2);
        System.out.println("There are two real roots at:"  + root_1 + "and"  + root_2);
        }

    if (discrim < 0){

        x1 = (-b + d) / (2 * a);
        x2 = (-b - d) / (2 * a);
        String root_1 = Double.toString(x1);
        String root_2 = Double.toString(x2);
        System.out.println("There are two imaginary roots at:" + root_1 + "and" + root_2);
        }
    }


}

Answer 1

@Smit 对于其中一个问题的看法是正确的，但还有第二个问题。

当 discrim 为负数时，

Math.sqrt(discrim) 将不起作用。您应该改用 Math.sqrt(Math.abs(discrim))。