Count the number of lines in a flat text file

CountLines.java

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.IOException;

// NOTE: adapted from http://bit.ly/2LOQwIP

public class CountLines {

  // private constructor in utility class
  private CountLines(){}

  public static int inTextFile (String fileName) {

    try (InputStream is = new BufferedInputStream(new FileInputStream(fileName))) {

      final int bufferSize = 4096; // 4kB
      byte[] c = new byte[bufferSize];

      int readChars = is.read(c);
      if (readChars == -1) return 0;

      int count = 0;
      while (readChars == bufferSize) {
        for (int ii = 0; ii < bufferSize; )
          if (c[ii++] == '\n') ++count;
        readChars = is.read(c);
      }

      while (readChars != -1) {
        for (int ii = 0; ii < readChars; ++ii)
          if (c[ii] == '\n') ++count;

        readChars = is.read(c);
      }

      return count == 0 ? 1 : count;

    } catch (IOException ex) {
      System.err.println("Cannot open file.");
      return -1;
    }
  }
}