Java : Read last n lines of a HUGE file

Question

I want to read the last n lines of a very big file without reading the whole file into any buffer/memory area using Java.

I looked around the JDK APIs and Apache Com

Answer 1

I had similar problem, but I don't understood to another solutions.

I used this. I hope thats simple code.

// String filePathName = (direction and file name).
File f = new File(filePathName);
long fileLength = f.length(); // Take size of file [bites].
long fileLength_toRead = 0;
if (fileLength > 2000) {
    // My file content is a table, I know one row has about e.g. 100 bites / characters. 
    // I used 1000 bites before file end to point where start read.
    // If you don't know line length, use @paxdiablo advice.
    fileLength_toRead = fileLength - 1000;
}
try (RandomAccessFile raf = new RandomAccessFile(filePathName, "r")) { // This row manage open and close file.
    raf.seek(fileLength_toRead); // File will begin read at this bite. 
    String rowInFile = raf.readLine(); // First readed line usualy is not whole, I needn't it.
    rowInFile = raf.readLine();
    while (rowInFile != null) {
        // Here I can readed lines (rowInFile) add to String[] array or ArriyList.
        // Later I can work with rows from array - last row is sometimes empty, etc.
        rowInFile = raf.readLine();
    }
}
catch (IOException e) {
    //
}