Split comma-separated file per line into Array

Question

Goal: I'm trying to process a .txt file into a String[]. File must be read per line, spliced on "," and stored in array. Each element (6 elements per line) must have it's own index in the array and must individually be accessible.

File (partially):

210,20140101,    1,   60,   67,   -1
210,20140101,    2,   60,   65,    0
210,20140101,    3,   60,   58,    0
210,20140101,    4,   60,   56,    0
210,20140101,    5,   60,   49,    0
210,20140101,    6,   60,   53,    0
210,20140101,    7,   60,   55,    0
210,20140101,    8,   70,   59,    0

Code so far:

try (BufferedReader br = new BufferedReader(new FileReader(path))) {
    for (String line; (line = br.readLine()) != null;) {
        counter++;
        if (counter > 51) {
            line = br.readLine();
            line = line.trim();
            list = Arrays.asList(line.split("\\s*,\\s*"));
        }
    }
}

for (String x : list) {
    System.out.println(x);
}

Output so far:

391
20141231
24
20
1
0

Which is exactly what I need, but for every line (stored in a String array). Only the last line of the file is stored in the array using the code above.

I've already tried the suggestions here and here. Any suggestions or hints?

Answer 1

list = Arrays.asList(line.split("\\s*,\\s*"));

This line just replaces existing elements, so you need to append elements, never do = to add elements to list variable.

Probably this can help:

list.addAll(Arrays.asList(line.split("\\s*,\\s*")));

Answer 2

This should work:

try {
    BufferedReader br = new BufferedReader(new FileReader("D:\\a.txt"));
    int counter = 0;
    ArrayList<String> list = new ArrayList<String>();
    for (String line; (line = br.readLine()) != null;) {
        counter++;

        if (counter > 51) {
            line = line.trim();
            list.addAll(Arrays.asList(line.split("\\s*,\\s*")));
        }
    }

    String[] array = new String[list.size()];
    array = list.toArray(array);

    for (int i = 0; i < array.length; i++) {
        System.out.println(array[i]);
    }
} catch(Exception e) {
    System.out.println(e);
}

Answer 3

You should try using this.

    private BufferedReader innerReader;
public List<String> loadFrom(Reader reader)
        throws IOException {
    if(reader == null)
    {
        throw new IllegalArgumentException("Reader not found");
    }
        this.innerReader = new BufferedReader(reader);
    List<String> result = new ArrayList<String>();
    String line;
    try
    {
    while((line = innerReader.readLine()) != null)
    {
        if (line == null || line.trim().isEmpty())
            throw new IllegalArgumentException(
                    "line null");

        StringTokenizer tokenizer = new StringTokenizer(line, ",");
        if (tokenizer.countTokens() < 6)
            throw new IllegalArgumentException(
                    "Token number (<= 6)");
        String n1 = tokenizer.nextToken(",").trim();
        String n2 = tokenizer.nextToken(",").trim();
        String n3 = tokenizer.nextToken(",").trim();
        String n4 = tokenizer.nextToken(",").trim();
        String n5 = tokenizer.nextToken(",").trim();
        String n6 = tokenizer.nextToken(",\n\r").trim();
        StringBuilder sb = new StringBuilder();
        sb.append(n1 + "," + n2 + "," + n3 + "," + n4 + "," + n5 + "," + n6);
        result.add(sb.toString());
    }
    } catch (NoSuchElementException e) {
        throw new  IllegalArgumentException(e);
    }
    return result;
}

Answer 4

If you're using Java7, you could use the new Files API to read the file more easily:

public List<List<String>> readValuesJava7() {
  Path path = Paths.get(URI.create("/tmp/coco.txt"));
  List<String> rawLines = new ArrayList<>();
  try {
    rawLines = Files.readAllLines(path);
  } catch (IOException e) {
    e.printStackTrace();
  }
  List<List<String>> lines = new ArrayList<>();
  for (String rawLine : rawLines) {
    List<String> line = new ArrayList<>();
    for (String col : rawLine.split(","))
      line.add(col.trim());
    lines.add(line);
  }
  return lines;
}

If you're using Java8, you can combine that with the new Streams API like so:

public List<List<String>> readValuesJava8() {
  Path path = Paths.get(URI.create("/tmp/coco.txt"));
  Stream<String> rawLines = Stream.empty();
  try {
    rawLines = Files.lines(path);
  } catch (IOException e) {
    e.printStackTrace();
  }
  return rawLines
      .map(line -> line.split(","))
      .map(cols -> Stream.of(cols).map(String::trim).collect(Collectors.toList()))
      .collect(Collectors.toList());
}

Answer 5

You can use a two dimensional array of String to represent the table you are trying to read. I use an ArrayList to read the file since you won't know how many rows you have until reaching the end of the file. I convert the ArrayList to an array at the end of the code sample.

List<String[]> resultList = new ArrayList<String[]>();
int counter = 0;
try (BufferedReader br = new BufferedReader(new FileReader(path))) {

    for (String line; (line = br.readLine()) != null;) {
        counter++;

        if (counter > 51) {                           // ignore the first 51 lines
            line = br.readLine();
            line = line.trim();
            resultList.add(line.split("\\s*,\\s*"));
        }
    }
}

String[][] resultArray = new String[counter][6];      // convert ArrayList of String[]
resultArray = resultList.toArray(resultArray);        // to an array

Output:

System.out.println(resultArray[0][4]); // prints 67
System.out.println(resultArray[4][1]); // prints 20140101
System.out.println(resultArray[6][2]); // prints 7