import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;

public class TestWCJava2 {
    public static void main(String args[]) {
        try {
            new TestWCJava2().run(args);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    void run(String files[]) throws IOException {
        wordCount("/tmp/three"); // hope JIT kicks in here (and hence we exclude timing it later).

        long t0 = System.nanoTime();
        for(String file: files) {
            wordCount(file);
        }
        long t1 = System.nanoTime();
        System.out.println("Elapsed time: " + (t1 - t0) / 1000 + "us");
    }

    int wordCount(String fileName) throws IOException {
        File f = new File(fileName);
        FileChannel fc = new RandomAccessFile(f, "r").getChannel();
        MappedByteBuffer mem = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());

        int nlines = 0;
        byte newline = '\n';

        for(long i = 0; i < fc.size(); i++) {
            if(mem.get() == newline)
                nlines += 1;
        }

        System.out.println(fileName + " lines: " + nlines);

        return nlines;
    }
}