code: public void ensureIndex(DBObject keys, String name, boolean unique) throws MongoException {
          dbCollection.ensureIndex(keys, name, unique);
      }
docs: Ensures an index on this collection (that is, the index will be created if it does not exist).
  
  @param keys   fields to use for index
  @param name   an identifier for the index. If null or empty, the default name will be used.
  @param unique if the index should be unique
  @throws MongoException If an error occurred