code: public void startBookie(int bookieIndex) throws Exception {
          Preconditions.checkState(this.servers.size() > 0, "No Bookies initialized. Call startAll().");
          Preconditions.checkState(this.servers.get(0) == null, "Bookie already running.");
          this.servers.set(bookieIndex, runBookie(this.bookiePorts.get(bookieIndex)));
          log.info("Bookie {} stopped.", bookieIndex);
      }
docs: Restarts the BookieService with the given index.
  
  @param bookieIndex The index of the bookie to restart.
  @throws Exception If an exception occurred.