Question

import java.util.Scanner;

import java.io.File;

public class Exception2 {

       public static void main(String[] args) {

              int total = 0;

              int num = 0;

              File myFile = null;

              Scanner inputFile = null;

              myFile = new File("inFile.txt");

              inputFile = new Scanner(myFile);

              while (inputFile.hasNext()) {

                     num = inputFile.nextInt();

                     total += num;

              }

              System.out.println("The total value is " + total);

       }

}

/*

1. In the first program, the Scanner may throw an exception due to bad data entry. This is an unchecked exception for which the Java runtime system will handle by aborting the program and displaying the exception information. Other methods may throw checked exceptions. A checked exception must be handled. Type the program (Exception2.java) above and compile. You should receive a compilation error stating that the an particular exception must be caught or declared to be thrown.
2. So we will test the program knowing that the input file does not exist. Add a try/catch block such that if the input file is not found, report the problem and display a total of 0. Use the getMessage() method of the exception object to report the problem.
3. Next create an ASCII plain text-based file named inFile.txt using a text editor. Enter only integer values into the file and save the file in the same folder as the program (if you are using a IDE, then put it in the main project folder). Run the program to verify that the program functions correctly with a valid input file.
4. Any number of catch clauses may be coded for a single try block. Add another catch clause to catch the same exception as in the Exception1 program immediately before or after the file exception clause you just added. Remember to import the exception class and to clear the scanner buffer.
5. Modify the inFile.txt file to include an error (a non integer value). Run and test the program. As soon as an exception occurs, the catch clause is executed. Since the exception catch clause is outside of the read loop (step 4 above), the first invalid piece of data will cause the program to end without reading the remainder of the file.

Any number of try blocks may be coded with each having a least one catch clause. Rather than catching the data exception outside the loop, move it inside the loop. This will allow the program to report the invalid data, resume processing, and produce correct results for all of the valid data given. Add a new try block within the while loop and remove the exception catch block from Step 4. End result is one try/catch for the file issue and another try/catch for the bad data read by Scanner */

Answer 1

Answer 1:

import java.util.Scanner;

import java.io.File;
import java.io.FileNotFoundException;

public class Exception2 {

   public static void main(String[] args) {

       int total = 0;

       int num = 0;

       File myFile = null;

       Scanner inputFile = null;

       myFile = new File("inFile.txt");

       try {
           inputFile = new Scanner(myFile);

           while (inputFile.hasNext()) {

               num = inputFile.nextInt();

               total += num;

           }
       } catch (FileNotFoundException e) {
           System.out.println(e.getMessage());
       }
       System.out.println("The total value is " + total);

   }

}

With Valid File:

With Invalid Data:

import java.util.InputMismatchException;
import java.util.Scanner;

import java.io.File;
import java.io.FileNotFoundException;

public class Exception2 {

   public static void main(String[] args) {

       int total = 0;

       int num = 0;

       File myFile = null;

       Scanner inputFile = null;

       myFile = new File("inFile.txt");

       try {
           inputFile = new Scanner(myFile);

           while (inputFile.hasNext()) {
               num = inputFile.nextInt();
               total += num;

           }
       } catch (FileNotFoundException e) {
           e.printStackTrace();
       } catch (InputMismatchException e) {
           System.out.println(e.getMessage());
       }
       System.out.println("The total value is " + total);

   }

}