Question

Assignment 11 –
Exceptions, Text Input/Output - Random Numbers

Revised 9/2019

Chapter 12 discusses Exception Handling and Input/Output. Using try/catch/finally statement to handle exceptions, or declare/throw an exception as needed, create the following program:

Create an array of 25 random numbers between 0 & 250 formatted to a field width of 10 & 4 decimal places (%10.4f). Use the formula Math.random() * 250. Display the array of random numbers on the console and also write to a file.

Prompt the user for an integer, and then display the random number located at that index of the array. If the specified index is out of bounds, display the message The index is out of bounds in addition to the Java compiler out of bounds exception message. The random numbers and all results should be written to the console as well as to a file. Also, display the file path using the File method getAbsolutePath.

*Note: for those already familiar with Java programming, please use only concepts discussed up to this point.

Before starting this lab, be sure to refer to the “How to Submit Assignments” document in eLearn for proper documentation, indention, naming conventions, etc. Points may be deducted if submitted incorrectly.

REMINDER: Any sources you use besides the textbook, class demo files, or the instructor must be documented in your program with details such as the scope of help received & URL.

Required project name: LastnameFirstname11 Required package name: chap12
Required class names: RandomNumbers

Your program and the text in the file should look similar to the 3 program runs below (user input in bold):

24.5294

80.8706 147.1332

...(additional random numbers edited out) 72.8478

224.3029 89.4630

Enter an index: 0

The element at index 0 is 24.5294
(finally clause) Scanner object is closed
File path: C:\Users\John\Desktop\myJavaWorkspace\SmithJohn11\randNums.txt

--------------

(run the program again to get another set of random numbers) Enter an index: 24

The element at index 24 is 120.3913
(finally clause) Scanner object is closed
File path: C:\Users\John\Desktop\myJavaWorkspace\SmithJohn11\ randNums.txt

-----------------

(run the program again to get another set of random numbers) Enter an index: 25
The index chosen is out of bounds java.lang.ArrayIndexOutOfBoundsException: 25

(finally clause) Scanner object is closed
File path: C:\Users\John\Desktop\myJavaWorkspace\SmithJohn11\ randNums.txt

Answer 1

import java.io.FileWriter;
import java.util.Scanner;

public class Main {
    public static void main(String args[]) throws Exception {
        double arr[] = new double[25];
        FileWriter writer = new FileWriter("randNums.txt");
        Scanner in = new Scanner(System.in);

        for (int i = 0; i < 25; i++) {
            arr[i] = Math.random() * 250;
            System.out.printf("%10.4f   ", arr[i]);
            writer.write(String.format("%10.4f   ", arr[i]));
        }
        System.out.print("\n\nEnter an index: ");
        int index = in.nextInt();
        try {
            double element = arr[index];
            System.out.println("The element at index " + index + " is " + String.format("%10.4f   ", element));
            writer.write("The element at index " + index + " is " + String.format("%10.4f   ", element));
        } catch (IndexOutOfBoundsException e) {
            System.out.println("The index chosen in out of bounds " + e);
        }

        in.close();
        writer.close();
    }
}