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 found RandomAccessFile and other Buffer Reader classes too slow for me. Nothing can be faster than a tail -<#lines>. So this it was the best solution for me.

public String getLastNLogLines(File file, int nLines) {
    StringBuilder s = new StringBuilder();
    try {
        Process p = Runtime.getRuntime().exec("tail -"+nLines+" "+file);
        java.io.BufferedReader input = new java.io.BufferedReader(new java.io.InputStreamReader(p.getInputStream()));
        String line = null;
    //Here we first read the next line into the variable
    //line and then check for the EOF condition, which
    //is the return value of null
    while((line = input.readLine()) != null){
            s.append(line+'\n');
        }
    } catch (java.io.IOException e) {
        e.printStackTrace();
    }
    return s.toString();
}