public static  void main(String[] args) 
{
    String usage = "java org.apache.lucene.demo.DeleteFiles < unique_term >";
    if (args.length == 0) {
      System.err.println("Usage: " + usage);
      System.exit(1);
    }
    try {
      Directory directory = FSDirectory.open(new File("index"));
      IndexReader reader = IndexReader.open(directory, false); // we don't want read-only because we are about to delete
      Term term = new Term("path", args[0]);
      int deleted = reader.deleteDocuments(term);
      System.out.println("deleted " + deleted +
 			 " documents containing " + term);
      // one can also delete documents by their internal id:
      /*
      for (int i = 0; i <  reader.maxDoc(); i++) {
        System.out.println("Deleting document with id " + i);
        reader.delete(i);
      }*/
      reader.close();
      directory.close();
    } catch (Exception e) {
      System.out.println(" caught a " + e.getClass() +
			 "\n with message: " + e.getMessage());
    }
}

Deletes documents from an index that do not contain a term.