code: public void createIndex(final DBObject keys, @Nullable final String name, final boolean unique) {
          DBObject options = new BasicDBObject();
          if (name != null && name.length() > 0) {
              options.put("name", name);
          }
          if (unique) {
              options.put("unique", Boolean.TRUE);
          }
          createIndex(keys, options);
      }
docs: Forces creation of an index on a set of fields, if one does not already exist.
  
  @param keys   a document that contains pairs with the name of the field or fields to index and order of the 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 the operation failed
  @mongodb.driver.manual /administration/indexes-creation/ Index Creation Tutorials