Going through a txt file and finding sum of integers with exception

Question

I have program that is suppose to ask the user what txt file, go through the txt file and find all parsable ints and average them. I have the following code below, but it's giving me a bunch of errors. What is the cause of all these errors?

The txt file is: 5 15 312 16 eight seven 44 eighty-five thousand and sixty-two 13 98 93

import java.util.Scanner;


public class Ch12Pt2 {
public static void main(String[] args) throws NumberFormatException {
Scanner input = new Scanner(System.in);
System.out.print("Enter filename: ");
String filename = input.nextLine();
Scanner file = new Scanner(filename);

if(file.nextLine().equals(""))
{
    System.err.println("Could not find file:" + filename);
    System.exit(1);
}

do {
      try {
            int total = 0;
            int count = 0;
        int num = file.nextInt();
        total = num + total;

        //Display the results
        System.out.println("The number of parsable numbers: " + count);
        System.out.println("Average values: " + (total / count));




      } 
      catch (NumberFormatException ex) {
        System.out.println("Cannot parse " + num + " as an integer.");
        file.nextInt();
      }

    } while (file.hasNextInt());

// Close the files
input.close();
file.close();
   }
}

Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextInt(Scanner.java:2117)
at java.util.Scanner.nextInt(Scanner.java:2076)
at Ch12Pt2.main(Ch12Pt2.java:21)

Answer 1

If you look at the JavaDoc for the constructor you used, you will that it "Constructs a new Scanner that produces values scanned from the specified string." What you want is Scanner#Scanner(File source), "...a new Scanner that produces values scanned from the specified file".

Do not use do-while, it will through a null pointer if your file does not have any integers. Use while instead. Also, do not initialize any of your variables inside the loop. This will cause them to re-initialize at ever iteration.

What is the point of file.nextInt(); in your catch block? It causes the program to skip an extra integer. Remove it. Furthermore, do not call input.close();, you do not want to close System.in.

    @SuppressWarnings("resource")
    Scanner input = new Scanner(System.in);
    System.out.println("Enter filename: ");
    File file = new File(input.nextLine());

    /*
     * Check file existence before constructing your scanner. This will prevent a
     * FileNotFoundException. Notice, I used File#exists and the NOT operator '!'
     */
    if (!file.exists()) {
        System.err.println("Could not find file: " + file.getName());
        System.exit(0);
    }

    Scanner scanner = new Scanner(file);

    // Initialize variables outside of loop.
    int num = 0;
    int total = 0;
    int count = 1;
    // No do-while
    while (scanner.hasNextInt()) {
        try {
            num = scanner.nextInt();
            total += num;

            // Display the results
            System.out.println("The number of parsable numbers: " + count);
            System.out.println("Average values: " + (total / count));

            // count is pointless unless you increase it after every number.
            count++;
        } catch (NumberFormatException ex) {
            System.out.println("Cannot parse " + num + " as an integer.");
        }

    }

    // Close the files
    scanner.close();

Finally, as Mad Programmer pointed out, "eight seven" and "eighty-five thousand and sixty-two" are not numbers, thus Scanner#nextInt will not include them. A work around is to use Scanner#nextLine and parse accordingly. Something like this: How to convert words to a number?

Answer 2

Your code is all most all wrong. I have reworked it now it works.

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Scanner;


public class Ch12Pt2 {
    public static void main(String[] args) throws NumberFormatException, FileNotFoundException {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter filename: ");
        String filename = input.nextLine();
        Scanner file = new Scanner(new FileReader(filename));
        int num =0;
        int count =0;
        int total =0;

        if(file.nextLine().equals(""))
        {
            System.err.println("Could not find file:" + filename);
            System.exit(1);
        }

        while (file.hasNextInt()){
            try {
                    num = file.nextInt();
                    total = num + total;
                   count++;


            }
            catch (NumberFormatException ex) {
                System.out.println("Cannot parse " + num + " as an integer.");
            }

        }

// Close the files
        input.close();
        file.close();
        System.out.println("The number of parsable numbers: " + count);
        System.out.println("Average values: " + (total / count));
    }

}

Answer 3

Scanner file = new Scanner(filename);

Exception in thread "main" java.util.NoSuchElementException

If you're reading data from a text file using a Scanner you need to specify a File, not a string, which is why you're getting the above error.

Use:

Scanner scanner = new Scanner(new FileReader("foo.txt"));

And then recursively go through the text file like this:

while(scanner.hasNext())

Your code:

while (file.hasNextInt());

Will not work because the hasNextInt() method will stop processing the text file when it encounters anything other than an integer.

System.out.println("Cannot parse " + num + " as an integer.");

Variable num is defined in a different scope to the body that handles the exception. An additional error will be thrown because num is not defined within the NumberFormatException body.

The txt file is: 5 15 312 16 eight seven 44 eighty-five thousand and sixty-two 13 98 93

If the items in the text file are on the same line it would be better to use the split method to get all elements and then detect whether they're numbers or not.

String line = sc.nextLine();
String elements = line.split(" ");
for (String e : elements) {
 // add if int, or continue iteration
}

Otherwise, try something along the lines of:

int sum = 0;
int numElements = 0;
Scanner scanner = new Scanner(new FileReader("path-to-file"));
while (scanner.hasNext()) {
    try {
      int temp = Integer.parseInt(sc.nextLine());
      sum += temp;
      numElements += 1;
    }catch(NumberFormatException e) {
      continue;
    } 
}

System.out.println("Mean: "+ (sum/numElements));