Question

I am a student and this is my second week of Java. the assignment is to get data from the keyboard, for a student name, ID, and three test scores. Then display the primary data using JOptionPane. I believe that I have all of that done. I’ve taken the assignment a little further so that I can learn about unit testing as well.

The problem is that the ID and test scores are supposed to be numbers. If a non-numeric value is entered I get IOExceptions. I think I need to use try/catch but everything I have seen so far is leaving me confused. Could someone please break down how the try/catch works so that I can understand it?

//Import packages
import java.io.*;
import java.util.Scanner;
import javax.swing.JOptionPane;

/**
 *
 * @author Kevin Young
 */

public class StudentTestAverage {

    //A reusable method to calculate the average of 3 test scores
    public static double calcAve(double num1, double num2, double num3){
        final double divThree = 3;
        return (num1 + num2 + num3 / divThree);
    }

    //A method to turn a doule into an integer
    public static int trunAve(double num1){
        return (int) num1;
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws IOException{
        //Input variables
        String strStudentName = "";
        int intStudentID = 0;
        double dblScore1 = 0.0;
        double dblScore2 = 0.0;
        double dblScore3 = 0.0;
        String strNumber = ""; //Receives a string to be converted to a number

        //Processing variables
        double dblAverage = 0.0;
        int intAverage = 0;

        /**
         * Create objects that read keyboard data from a buffer
         */

        //Create the reader and Buffer the input stream to form a string
        BufferedReader brObject = 
                new BufferedReader(new InputStreamReader(System.in));

        //Get the student's name
        do{
            System.out.print("Please enter the student's name?");
            strStudentName = brObject.readLine();
        }while(strStudentName.equals(""));

        //Use the scanner to get the student ID
        //this method converts the string to an Integer
        Scanner scan = new Scanner(System.in);

        do{
            System.out.print("Please enter the student's ID?");
            intStudentID = scan.nextInt();
       }while(Double.isNaN(intStudentID));
       /*
        * The above do while loop with the Scanner isn't working as
        * expected. When non-numeric text is entered it throws an 
        * exception. Has the same issue when trying to use parseInt().
        * Need to know how to handle exceptions.
        */


       /**
        * Us JOption to get string data and convert it to a double
        */
        do{
            strNumber = JOptionPane.showInputDialog("Please enter the first test score?");
            dblScore1 = Double.parseDouble(strNumber);
        }while(Double.isNaN(dblScore1));

        do{
            strNumber = JOptionPane.showInputDialog("Please enter the second test score?");
            dblScore2 = Double.parseDouble(strNumber);
        }while(Double.isNaN(dblScore2));

        do{
            strNumber = JOptionPane.showInputDialog("Please enter the third test score?");
            dblScore3 = Double.parseDouble(strNumber);
        }while(Double.isNaN(dblScore3));

        //Calculate the average score
        dblAverage = calcAve(dblScore1, dblScore2, dblScore3);

        //Truncate dblAverage making it an integer
        intAverage = trunAve(dblAverage);


        /**
         * Display data using the JOptionPane
         */
        JOptionPane.showMessageDialog(
                null, "Student " + strStudentName + " ID " + 
                Integer.toString(intStudentID) + " scored " +
                Double.toString(dblScore1) + ", " + 
                Double.toString(dblScore2) + ", and " +
                Double.toString(dblScore3) + ".\n For an average of " +
                Double.toString(dblAverage));

        //Output the truncated average
        System.out.println(Integer.toString(intAverage));
    }
}

Answer 1

You should not use try-catck block to check number format. It is expensive. You may use following code portion. It could be more usefull.

    String id;
    do{
        System.out.print("Please enter the student's ID?");            
        id = scan.next();
        if(id.matches("^-?[0-9]+(\\.[0-9]+)?$")){
            intStudentID=Integer.valueOf(id);
            break;
        }else{
            continue;
        }

   }while(true);