static  void indexDocs(IndexWriter writer,
    File file) throws IOException 
{
    // do not try to index files that cannot be read
    if (file.canRead()) {
      if (file.isDirectory()) {
        String[] files = file.list();
        // an IO error could occur
        if (files != null) {
          for (int i = 0; i <  files.length; i++) {
            indexDocs(writer, new File(file, files[i]));
          }
        }
      } else {
        System.out.println("adding " + file);
        try {
          writer.addDocument(FileDocument.Document(file));
        }
        // at least on windows, some temporary files raise this exception with an "access denied" message
        // checking if the file can be read doesn't help
        catch (FileNotFoundException fnfe) {
          ;
        }
      }
    }
}

 public static  void main(String[] args) 
{
    String usage = "java org.apache.lucene.demo.IndexFiles < root_directory >";
    if (args.length == 0) {
      System.err.println("Usage: " + usage);
      System.exit(1);
    }
    if (INDEX_DIR.exists()) {
      System.out.println("Cannot save index to '" +INDEX_DIR+ "' directory, please delete it first");
      System.exit(1);
    }
    final File docDir = new File(args[0]);
    if (!docDir.exists() || !docDir.canRead()) {
      System.out.println("Document directory '" +docDir.getAbsolutePath()+ "' does not exist or is not readable, please check the path");
      System.exit(1);
    }
    Date start = new Date();
    try {
      IndexWriter writer = new IndexWriter(FSDirectory.open(INDEX_DIR), new StandardAnalyzer(Version.LUCENE_CURRENT), true, IndexWriter.MaxFieldLength.LIMITED);
      System.out.println("Indexing to directory '" +INDEX_DIR+ "'...");
      indexDocs(writer, docDir);
      System.out.println("Optimizing...");
      writer.optimize();
      writer.close();
      Date end = new Date();
      System.out.println(end.getTime() - start.getTime() + " total milliseconds");
    } catch (IOException e) {
      System.out.println(" caught a " + e.getClass() +
       "\n with message: " + e.getMessage());
    }
}

Index all text files under a directory.