Thread: Using for loop to read in data from text file using Scanner class

Hi guys,

I'm currently stuck on a programming assignment which requires me to read in data from a text file then process it. The file looks like this:

CS1 2012 Group 1
8
5,5,5,6,5,8,9,5,6,8, good, very good, excellent, good
7,7,8,7,6,7,8,8,9,7,very good, Good, excellent, very good
8,7,6,7,8,7,5,6,8,7 ,GOOD, VERY GOOD, GOOD, AVERAGE
9,9,9,8,9,7,9,8,9,9 ,Excellent, very good, very good, excellent
7,8,8,7,8,7,8,9,6,8 ,very good, good, excellent, excellent
6,5,6,4,5,6,5,6,6,6 ,good, average, good, good
7,8,7,7,6,8,7,8,6,6 ,good, very good, good, very good
5,7,6,7,6,7,6,7,7,7 ,excellent, very good, very good, very good

The first 2 lines are read in then assigned to fields, the remaining lines are the ones I have to process. I've been told to use .useDelimiter("[ ]*(,)[ ]*") but so far haven't really been able to put it to good use.

Once the data has been read in I have to convert the Strings into integers using a switch statement and work out an average feedback score e.g excellent = 5 very good = 4 good =3. Maybe i'm just not thinking clear but I've already spent about 5 hours trying to figure this out to no avail so any guidance would be appreciated. Thanks!

Thanks for your responses. This is my attempt:

    public void readMarksData(String fileName, int numberOfStudents, int responsesPerStudent) throws FileNotFoundException
    {
        int feedbackScore;
        studentResponses = new int[numberOfStudents][responsesPerStudent]; //Creates 2D array
        File dataFile = new File(fileName);
        Scanner scanner = new Scanner (dataFile);
 
        cohort = scanner.nextLine(); //Assigns the first line of the text file to the field "cohort"
        System.out.println (cohort);
        int numberOfResponses = scanner.nextInt(); //Assigns the second line of the text file to the field "numberOfResponses"
        System.out.println (numberOfResponses);
 
        scanner.useDelimiter("[ ]*(,)[ ]*");      
 
        for (int row = 0; row < studentResponses.length; row++)
        {
            for (int column = 0; column < studentResponses[0].length; column++){
                studentResponses[row][column] = scanner.nextInt();
                System.out.print(studentResponses[row][column]); 
            }          
 
        }
        scanner.close();
 
    }

Once it gets to the studentResponses[row][column] = scanner.nextInt(); part I get this error: "java.util.InputMismatch exception: null(in java.util.Scanner)".

The loop that prints out everything being read in is

            for (int column = 0; column < studentResponses[0].length; column++){
                studentResponses[row][column] = scanner.nextInt();
                System.out.print(studentResponses[row][column]); 
            }

Everything else above the loop works

I see, so what modifications would you suggest I make to my code?

I think this should work, basically it's going to print out everything again separated by a space rather than comma and put a tab space between the numbers and the strings. However I'm still getting the same error as before and can't figure out why I'm getting it

    public void readMarksData(String fileName, int numberOfStudents, int responsesPerStudent) throws FileNotFoundException
    {
        int feedbackScore;
        studentResponses = new int[numberOfStudents][responsesPerStudent];
        File dataFile = new File(fileName);
 
        Scanner scanner = new Scanner (dataFile);
 
        cohort = scanner.nextLine();
        System.out.println (cohort);
        int numberOfResponses = scanner.nextInt();
        System.out.println (numberOfResponses);
        scanner.useDelimiter(",");      
 
        for (int row = 0; row < 8; row++)
        {
            Scanner scanner2 = new Scanner(scanner.nextLine());
            for (int column = 0; column < studentResponses[0].length-4; column++)
            {
                scanner2.useDelimiter(",");
                studentResponses[row][column] = scanner2.nextInt();
                System.out.print(" "+studentResponses[row][column]); 
            }
            System.out.print("\t");
            for (int column = studentResponses[0].length-4; column < studentResponses[0].length; column++)
            {
                scanner2.useDelimiter("[ ]*(,)[ ]*");
                String test = scanner.next();
                System.out.print(" "+test);
 
            }
            scanner2.close();
        }
        scanner.close();   
     }

Well I've asked someone in my class to give me some pointers so I'm just trying out his method. Yeah I usually use studentResponses.length rather than a number, the 8 was just there for testing purposes, I've changed it back now.

Basically, scanner will pass a whole line of data to scanner2, the first inner loop will loop from element 1 to 10 which are the integer elements which is why I have studentResponses[0].length-4 because there are 14 elements in total and the last 4 are Strings. The second inner loop will loop from 10 to 14 and read in the Strings.

I'm currently just getting the program to tokenize the data properly and print it to the terminal, the rest is quite easy

No, I get the error everytime it gets to the line studentResponses[row][column] = scanner2.nextInt();

I mentioned this error earlier, the full content of the console is: java.util.InputMismatch exception: null(in java.util.Scanner)

Oh so sorry, yeah the Cohort and numberOfResponses get printed out fine. The program prints those two lines, then goes to print the actual data, starting with the integers, and that's when the error appears.

    public void readMarksData(String fileName, int numberOfStudents, int responsesPerStudent) throws FileNotFoundException
    {
        int feedbackScore;
        studentResponses = new int[numberOfStudents][responsesPerStudent];
        File dataFile = new File(fileName);
 
        Scanner scanner = new Scanner (dataFile);
 
        cohort = scanner.nextLine();
        int numberOfResponses = scanner.nextInt();
        System.out.println (cohort);
        System.out.println (numberOfResponses);
        scanner.useDelimiter(",");      
 
        for (int row = 0; row < studentResponses.length; row++)
        {
            Scanner scanner2 = new Scanner(scanner.nextLine());
            for (int column = 0; column < studentResponses[0].length-4; column++)
            {
                scanner2.useDelimiter(",");
                studentResponses[row][column] = scanner2.nextInt();
                //System.out.print(" "+studentResponses[row][column]); 
                //System.out.print(scanner2.nextInt());
            }
            System.out.print("\t");
            for (int column = studentResponses[0].length-4; column < studentResponses[0].length; column++)
            {
                 scanner2.useDelimiter("[ ]*(,)[ ]*");
                 String feedback = scanner2.next();
                 switch (feedback.toLowerCase())
                 {
                     case ("Excellent"): studentResponses[row][column] = 5;
                     break;
                     case ("Very Good"): studentResponses[row][column] = 4;
                     break;
                     case ("Good"): studentResponses[row][column] = 3;
                     break;
                     case ("Average"): studentResponses[row][column] = 2;
                     break;
                     default: studentResponses[row][column] = 1;
 
                 }
            }
 
            scanner2.close(); 
        }
        scanner.close(); 
    }

The first line is 5,5,5,6,5,8,9,5,6,8, good, very good, excellent, good and I've set the delimiter to a comma so I would've thought it'd print the first integer before crashing since I can't see anything wrong with studentResponses[row][column]=scanner2.nextInt()

Originally Posted by Norm

What was the last thing printed before the error?
How many numbers were printed before the error?
What was being read when the error happened?
Was it a numeric value or a String?

CS1 2012 Group 1 - printed first using scanner.hasNextLine()
8 - printed second as int on a new line scanner.hasNextInt()
One number was printed before the error which is the 8
studentResponses[row][column]=scanner2.nextInt() was being read when the error happened

Here's a screenshot of everything, the attached file is horribly pixelated so use this link : http://i56.tinypic.com/1xxfnn.png