Question

I’m doing a code testing for a program that calculate the results for a quadratic equation

I need to have test data for the following situation, when a is not zero and d positive there is two possibilities which are in the code below, I need to find an example for the first satiation when Math.abs(b / a – 200.0) < 1.0e-4 , all the values that I have tried, excute the second one

                caption= "Two roots";
                if (Math.abs(b / a - 200.0) < 1.0e-4)
                {
                    System.out.println("first one");
                    x1 = (-100.0 * (1.0 + Math.sqrt(1.0 - 1.0 / (10000.0 * a))));
                    x2 = (-100.0 * (1.0 - Math.sqrt(1.0 - 1.0 / (10000.0 * a))));
                }
                else
                {
                    System.out.println("secrst one");

                    x1 = (-b - Math.sqrt(d)) / (2.0 * a);
                    x2 = (-b + Math.sqrt(d)) / (2.0 * a);
                }
            }
        }                            

Answer 1

Not sure what trouble you’re having. I wrote:

public class Quad
{
    public static void main(String[] args) {
        double a = Double.parseDouble(args[0]);
        double b = Double.parseDouble(args[1]);

        System.out.println(Math.abs(b/a - 200.0));

        if (Math.abs(b/a - 200.0) < 1.0e-4) {
            System.out.println("first one");
        }
        else {
            System.out.println("second one");
        }
    }
}

And some output:

animato:~/src/Java/SO$ java Quad 1 200
0.0
first one
animato:~/src/Java/SO$ java Quad 2 400
0.0
first one
animato:~/src/Java/SO$ java Quad -3 -600
0.0
first one