Creating a java program that given 3 terms as input(a,b,c) in that order prints their roots

问题

Wrie a method printRoots that given 3 terms as input(a,b,c) in that order prints their roots

We have the following given information

1. If b²-4ac is a positive number, your program should print “The two roots are X and Y” where X is the larger root and Y is the smaller root

2. If b²-4ac *equals 0*, the program should print. “The equation has one X” where X is the only root

3. If b²-4ac is a negative number, the program should print.” The equation has two roots(-X1 + Y1i) and (-X2 and Y2i)

   The term can be determined based on:

   • If b^2 - 4ac is a negative number, then the quadratic equation becomes: (-b+/- √C)/2a -This means the equation can be simplified to become (-b+/- √Ci)/2a where the square root is not a positive number

Calculate the coefficient and print that(i.e X1 is -b/2a and Y1 is sqrt(-C)/2i

Note: Not allowed to use Scanners for this question

Is it possible for someone to review my program and tell me where I have gone wrong and do i just remove my scanners to make it a program without scanners?

---

import java.util.Scanner;//delete this part after 
    public class findingRoots {
    public static void main(String[] args)
        {
        }
          public static double printRoots (){ //should it be double here or int? 
           //read in the coefficients a,b,and c 
          Scanner reader = new Scanner(System.in);
          int a=reader.nextInt();
         System.out.println("Enter the value of a");
          int b=reader.nextInt();
          System.out.println("Enter the value of b");
          int c=reader.nextInt();
          System.out.println("Enter the value of c");
          //now compte the discrimintat d 
           double discrimintant = d; 
          double X,Y; //root 1 & root 2, respectively
           // is the step double X,Y necessary? 
           double d = (b*b)-(4.0*a*c);
             if (d > 0.0){ 
             d = Math.sqrt(d);
             System.out.println("The two roots are X and Y");
             double X = (-b + d)/(2.0 * a ); //X= root 1, which is larger 
             double Y = (-b - d)/(2.0 *a); //Y= root 2, which is the smaller root 
             System.out.println("Root 1" = X "and" "Root 2" "=" Y);
           }
           else{
             if (d==0.0) //then...how to write?
               System.out.println("The equation has one root X")//where X is the only root 
            double X = (-b + 0.0)/(2.0 * a);//repeated root 
             System.out.println("Root" "=" X);
           }
           else{
             if(d < 0.0)
               System.out.println("The equation has two roots (-X1 + Y1i) and (-X2 +Y2i)");
             // where i represents the square root of negative 1 
             double X1 = -b/(2*a);
             double Y1 = (Math.sqrt(-C))/(2*a);
             double X2 = -b/(2*a);
             double Y2 = (-(Math.sqrt(-C)))/(2*a);
             double Y2 = (-(Math.sqrt(-C)))/(2*a);   
             System.out.println("Root 1" "=" (-X1 + Y1i) "and" "Root 2" "=" (-X2 +Y2i)");
           }
          }
      }

回答1:

you can pass input from command lines. You will get the data at args array

in public static void main(String[] args) here args refers to command line arguements

when you run a java program using

java MyApp arg1 arg2

in your main args[0] is arg1 and args[1] is arg2

So in your case run the app like following command

java findingRoots 1 2 3

and in main

int a= Integer.parseInt(args[0])

N.B I think you would like to validate the command line parameters. check both the args.length and if they are int or not

来源：https://stackoverflow.com/questions/16899771/creating-a-java-program-that-given-3-terms-as-inputa-b-c-in-that-order-prints