Using string tokenizer to set create arrays out of a text file?

Question

Hey. You may have recently seen a post by me looking for help, but I did it wrong before, so I am going to start fresh and begin at the basics.

I am trying to read a text file that looks like this:

FTFFFTTFFTFT
3054 FTFFFTTFFTFT
4674 FTFTFFTTTFTF
... etc

What I need to do is put the first line into a String as the answer key.

Next, I need to create an array with the student ID (the first numbers). Then, I need to create an array that is parallel to the student ID that contains the student's answers.

Below is my code, and I can't quite figure out how to get it to work like this, and I was wondering if someone could help me out with it.

public static String[] getData() throws IOException {
      int[] studentID = new int[50];
      String[] studentAnswers = new String[50];
      int total = 0;

      String line = reader.readLine();
      strTkn = new StringTokenizer(line);
      String answerKey = strTkn.nextToken();

      while(line != null) {
        studentID[total] = Integer.parseInt(strTkn.nextToken());
        studentAnswers[total] = strTkn.nextToken();
        total++;
      }
    return studentAnswers;
    }

So at the end of the day, the array structure should look like:

studentID[0] = 3054
studentID[1] = 4674
... etc

studentAnswers[0] = FTFFFTTFFTFT
studentAnswers[1] = FTFTFFTTTFTF

Thanks :)

Answer 1

Assuming you have opened the file correctly for reading (because I can't see how the reader variable is initialized or the type of the reader) and the contents of the file are well-formed (according to what you expect), you have to do the following:

  String line = reader.readLine();
  String answerKey = line;
  StringTokenizer tokens;
  while((line = reader.readLine()) != null) {
    tokens = new StringTokenizer(line);
    studentID[total] = Integer.parseInt(tokens.nextToken());
    studentAnswers[total] = tokens.nextToken();
    total++;
  }

Of course it would be best if you add some checks in order to avoid runtime errors (in case the contents of the file are not correct), e.g. try-catch clause around Integer.parseInt() (might throw NumberFormatException).

EDIT: I just notice in your title that you want to use StringTokenizer, so I edited my code (replaced the split method with the StringTokenizer).

Answer 2

You may want to think about...

• using the Scanner class for tokenizing the input
• using collection types (such as ArrayList) instead of raw arrays - arrays have their uses, but they aren't very flexible; an ArrayList has a dynamic length
• creating a class to encapsulate the student id and their answers - this keeps the information together and avoids the need to keep two arrays in sync

---

Scanner input = new Scanner(new File("scan.txt"), "UTF-8");
List<AnswerRecord> test = new ArrayList<AnswerRecord>();
String answerKey = input.next();
while (input.hasNext()) {
  int id = input.nextInt();
  String answers = input.next();
  test.add(new AnswerRecord(id, answers));
}