Question

please write JAVA code:

Your Own Exception Class

Write a text-based (non-GUI) program to read in file that contains only positive numbers and outputs to the screen the sum of all numbers.

Create your own exception class that describes the situation of a non-positive number. In your program, use this exception to handle this situation. Use other exception classes from the Java standard library to handle other I/O situations.

Answer 1

Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

// Numbers.java

import java.io.File;

import java.io.FileNotFoundException;

import java.util.Scanner;

public class Numbers {

              public static void main(String[] args) {

                           //defining scanner to read user input

                           Scanner scanner = new Scanner(System.in);

                           //prompting and getting file name

                           System.out.print("Enter file name: ");

                           String filename = scanner.nextLine();

                           try {

                                         //reinitializing scanner to read from file

                                         scanner = new Scanner(new File(filename));

                                         //initializing sum to 0

                                         int sum = 0;

                                         //looping until the end of file

                                         while (scanner.hasNextInt()) {

                                                       //reading integer

                                                       int n = scanner.nextInt();

                                                       //checking if n is negative

                                                       if (n < 0) {

                                                                    //throwing negative number exception

                                                                    throw new NegativeNumberException("Negative number found: "

                                                                                                + n);

                                                       }

                                                       //adding n to sum

                                                       sum += n;

                                         }

                                         //closing scanner

                                         scanner.close();

                                         //displaying sum

                                         System.out.println("Sum of all numbers is " + sum);

                           } catch (FileNotFoundException e) {

                                         //file not found

                                         System.err.println(e.getMessage());

                           } catch (NegativeNumberException e) {

                                         //negative number found in the file

                                         System.err.println(e.getMessage());

                           }

              }

}

/**

* class to represent an Exception when a negative value is found

*/

class NegativeNumberException extends Exception {

              public NegativeNumberException(String str) {

                           //passing error message to super class constructor

                           super(str);

              }

}

//OUTPUT when file does not exist

Enter file name: abc

abc (The system cannot find the file specified)

//OUTPUT when file exists and contains numbers 1 2 3 4 5 6 7 8

Enter file name: input.txt

Sum of all numbers is 36

//OUTPUT when file exists and contains numbers 1 2 3 4 5 -6 7 8

Enter file name: input.txt

Negative number found: -6