Getting integers out of a string containing words in java-CodePudding

Right now I have a string input along the lines of "Stern Brenda 90 86 45". I'm trying to find a way to get 90 86 and 45 out of that and assign them as ints to tests 3, 2, and 1 respectively to compute an average of them.

      while ((line = reader.readLine()) != null) {
          test3 = line.indexOf(-2, -1);
          test2 = line.indexOf(-5, -4);
          test1 = line.indexOf(-8, -7);

This is returning a value of -1 for each test (I tried using a regular expression to start from index -2 and go until another integer is found. Trying to get a two digit integer (as opposed to if I was just trying to get something like 5 or 6) is really whats throwing me off. Is using the .indexOf method the best way to go about getting these numbers out of the string? If so how am I using it incorrectly?

edit: I found a solution that was relatively simple.

      while ((line = reader.readLine()) != null) {
          String nums = line.replaceAll("[\\D]", "");
          test1 = Integer.parseInt(nums.substring(0,2));
          test2 = Integer.parseInt(nums.substring(2,4));
          test3 = Integer.parseInt(nums.substring(4,6));

For the input "Stern Brenda 90 86 45", this returns 90 for test1, 86 for test2, and 45 for test3 (all as integers).

CodePudding user response：

CheshireMoe almost has it right, but he's accessing a List like an array, which probably won't work. In his example:

Instead of:

  test3 = Integer.parseInt(tokens[tokens.length-1]);
  test2 = Integer.parseInt(tokens[tokens.length-2]);
  test1 = Integer.parseInt(tokens[tokens.length-3]);

Should be:

  test3 = Integer.parseInt(tokens.get(tokens.size()-1));
  test2 = Integer.parseInt(tokens.get(tokens.size()-2));
  test1 = Integer.parseInt(tokens.get(tokens.size()-3));

An easier solution might be just to split the array using the space:

while ((line = reader.readLine()) != null) {

  String [] tokens = line.split(" ");
  if (tokens.length != 5) {  // catch errors in your data!
     throw new Exception();  // <-- use this if you want to stop on bad data
     // continue;  <-- use this if you just want to skip the record, instead
  }
  test3 = Integer.parseInt(tokens[4]);
  test2 = Integer.parseInt(tokens[3]);
  test1 = Integer.parseInt(tokens[2]);
}

Based on your data, you might also consider putting in some validation like I've shown, to catch things like:

a value is missing (student didn't take one of the tests)
not all the grades were entered as numbers (i.e. bad characters)
first and last name both exist

CodePudding user response：

You could use a regular expression to parse the string. This just computes the average. You can also assign the individual values as you deem appropriate.

String s =  "Stern Brenda 90 86 45";
double sum = 0;

\\b - a word boundary
\\d - one or more digits
() - a capture group
matching on the string s

Matcher m = Pattern.compile("\\b(\\d )\\b").matcher(s);
int count = 0;

a long as find() returns true, you have a match
so convert group(1) to a double, add to sum and increment the count.

while (m.find()) {
    sum = Double.parseDouble(m.group(1));
    count  ;
}

When done, compute the average.

System.out.println(sum   " "   count); // just for demo purposes.
if (count > 0) { //just in case
   double avg = sum/count;
   System.out.println("Avg = "   avg);
}

prints

221.0 3
Avg = 73.66666666666667

Check out the Pattern class for more details.

Formatting the final answer may be desirable. See System.out.printf

CodePudding user response：

StringTokenizer is a very useful way to work with data strings that come files or streams. If your data is separated by a specific character (space in this case), StringTokenizer is a easy way to brake a large string into parts & iterate through the data.

Since you don't seem to care about the other 'words' in the line & have not specified if it will be a constant number (middle name?) my example puts all the tokens in an array to get the last three like in the question. I have also added the parseInt() method to convert from strings to int. Here is how you would tokenize your lines.

while ((line = reader.readLine()) != null) {

  List<String> tokens = new ArrayList<>();
  StringTokenizer tokenizer = new StringTokenizer(line, " ");
  while (tokenizer.hasMoreElements()) {
    tokens.add(tokenizer.nextToken());
  }

  test3 = Integer.parseInt(tokens[tokens.length-1]);
  test2 = Integer.parseInt(tokens[tokens.length-2]);
  test1 = Integer.parseInt(tokens[tokens.length-3]);
}