code: package linenbr7;
  
  import java.io.*;
  
  public class LineNbr7 {
  
      public static void main(String[] args) throws Exception {
          File f = new File(args[0]);
          if (!f.isFile() || !f.canRead())
              throw new IOException("can't read " + args[0]);
  
          BufferedReader br = new BufferedReader(new FileReader(f));
          try (LineNumberReader lnr = new LineNumberReader(br)) {
              String line = null;
              int lnum = 0;
              while ((line = lnr.readLine()) != null
                      && (lnum = lnr.getLineNumber()) < 7) {
              }
  
              switch (lnum) {
                  case 0:
                      System.out.println("the file has zero length");
                      break;
                  case 7:
                      boolean empty = "".equals(line);
                      System.out.println("line 7: " + (empty ? "empty" : line));
                      break;
                  default:
                      System.out.println("the file has only " + lnum + " line(s)");
              }
          }
      }
  }
  