Read a specific line form file in Java

Question

I really do not want to do a duplicate question, but none of the answers on SO were implementable in my problem.

The answer in this question:

How to read a file from a certain offset in Java?

uses RandomAccessFile, but the implementations I found need all the file lines to have the same length.

How can I get List lines = readLinesFromLine(file);?

I tried

private static List<String> readRandomAccessFile(String filepath, int lineStart, int lineEnd, int charsPerLine, String delimiter) {

    File file = new File(filepath);

    String data = "";
   

    int bytesPerLine = charsPerLine+2;

    try{

        RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r");

        for (int i = lineStart; i <lineEnd ; i++) {

            randomAccessFile.seek(bytesPerLine *i);
            data = randomAccessFile.readLine();
            dialogLineRead.add(data);
        }

        randomAccessFile.close();

    }catch (Exception e){
        e.printStackTrace();
    }

    String returnData = "";

    for (int i = 0; i < dialogLineRead.size(); i++) {

        returnData += dialogLineRead.get(i);
        returnData+=delimiter;
    }

    return returnData;

But like I said charsPerLine has to be the same for each line.

I tried to count the chars of each line in a file, and store it in a list, but with a log file of 2gb, that takes to much ram.

Any ideas?

Answer 1

For a standard text file where you don't know the line lengths in advance, there's really no way around reading the whole thing line by line, like in this answer, for example.