Question

Hello,

Could you please input validate this code so that the code prints an error message if the user enters in floating point numbers or characters or ANYTHING but VALID ints? And then could you please post a picture of the output testing it to make sure it works?

* Write a method called evenNumbers that accepts a Scanner 
 * reading input from a file with a series of integers, and 
 * report various statistics about the integers to the console. 
 * Report the total number of numbers, the sum of the numbers, 
 * the count of even numbers and the percent of even numbers. 
 * For example, if the input file contains the following text: 
 * 
 * 5 7 2 8 9 10 12 98 7 14 20 22
 * 
 * Then the method should produce the following console output: 
 * 
 * 12 numbers, sum = 214 
 * 8 evens (66.67%) 
 * 
 */ 

import java.util.*;
import java.io.*;

public class Chap6Ex02{
    public static void main (String[] args) throws FileNotFoundException{
        Scanner input = new Scanner(new File("integers.txt"));
        evenNumbers(input);               
    }
    
    public static void evenNumbers( Scanner inp){
        int count = 0;
        int sum   = 0;
        int evens = 0;
        while(inp.hasNextInt()){
            int num = inp.nextInt();
            count++;
            sum += num;
            if (num % 2 == 0){
                evens++;
            }
        }
        double percent = evens/count * 100;
        System.out.println(count + " numbers, sum = " + sum);
        System.out.println(evens + " evens (" + percent + "%)");
    }
}

Answer 1

Program:

import java.util.*;

import java.io.*;

public class Chap6Ex02{

public static void main (String[] args) throws FileNotFoundException{

Scanner input = new Scanner(new File("integers.txt"));

evenNumbers(input);

}

public static void evenNumbers(Scanner inp){

int count = 0;

int sum = 0;

int evens = 0;

boolean isValid = true;

//run a loop until end of file is reached

while(inp.hasNext())

{

//check is the value encountered is an integer or not, if integer proceed else print error message

if(inp.hasNextInt())

{

//read the integer

int num = inp.nextInt();

//increment the count numbers read

count++;

//add the integer to sum

sum += num;

//check if integer is even, if even increment count of evens

if (num % 2 == 0){

evens++;

}

}

//if an invalid value is encountered in the file

else

{

//display error message and terminate the loop

System.out.println("Error: Invalid values in input file.");

isValid = false;

break;

}

}

//display results only if all the values are valid

if(isValid)

{

double percent = (double)(evens)/(double)(count) * 100;

System.out.println(count + " numbers, sum = " + sum);

System.out.printf("%d evens (%.2f%%)", evens, percent);

//System.out.println(evens + " evens (" + percent + "%)");

}

}

}

Output:

Output when valid input is used

Output when invalid input is entered

Program screenshot: