Problem with a Try/catch exception

Question

Hello everyone here on the forums. I'm brand new to Java and have a bit of a problem with a try catch statement I'm making. In the following code if a user enters a non-integer number the program will display "Sorry, incompatible data." Problem is it gets caught in a loop and continues to display "Sorry, incompatible data." My aim with the try catch was if the user is not quite smart enough to understand quadratic programs don't use symbols and characters it would state it isn't correct and continue running the program.
Heres my code thus far:
package finishedquadraticprogram;
import java.util.*;
* @author Matt
public class quad {
     * @param args the command line arguments
    public static void main(String[] args) {
        boolean verification = true;
        double a, b, c, root1, root2, discriminant;
        Scanner keyInput = new Scanner(System.in);
        while ( verification)
        try
        System.out.println("a: ");
        a = keyInput.nextDouble();
        System.out.println("b: ");
        b = keyInput.nextDouble();
        System.out.println("c: ");
        c = keyInput.nextDouble();
        discriminant = Math.sqrt(b * b - 4 * a * c);
        root1 = (-b + discriminant) / 2 * a;
        root2 = (-b - discriminant) / 2 * a;
        verification = false;
        System.out.println("Root 1 = " +root1+ "\nRoot 2 = " +root2);
        } //try
        catch  (InputMismatchException iMe)
          System.out.println( "Sorry. incompatible data." );  
}I'm pretty sure the problem is something to do with the keyboard buffer, but I'm not sure what I need to do to either reset it or clear it, whichever one works. (Oh, and how would I go about making the program use complex numbers? I realize Java can't use complex numbers and will just display NaN ... any ideas how to make this work?)
Thanks a lot for all of your help guys, it's appreciated.

Answer 1

this is better:
package finishedquadraticprogram;
import java.util.*;
/** @author Matt */
public class quad
   private static final double TOLERANCE = 1.0e-9;
   /** @param args the command line arguments */
   public static void main(String[] args)
      boolean verification = true;
      double a, b, c, root1, root2, discriminant;
      Scanner keyInput = new Scanner(System.in);
      while (verification)
         try
            System.out.println("a: ");
            a = keyInput.nextDouble();
            System.out.println("b: ");
            b = keyInput.nextDouble();
            System.out.println("c: ");
            c = keyInput.nextDouble();
            discriminant = Math.sqrt(b * b - 4 * a * c);
            if (Math.abs(a) < TOLERANCE)
               root1 = 0.0;
               root2 = -c/b;
            else
               root1 = (-b + discriminant) / (2 * a);
               root2 = (-b - discriminant) / (2 * a);
            verification = false;
            System.out.println("Root 1 = " + root1 + "\nRoot 2 = " + root2);
         } //try
         catch (InputMismatchException iMe)
            System.out.println("Sorry. incompatible data.");
            keyInput.next();
}