code: public static Env<ByteBuffer> open(final File path, final int size,
                                       final EnvFlags... flags) {
      return new Builder<>(PROXY_OPTIMAL)
          .setMapSize(size * 1_024L * 1_024L)
          .open(path, flags);
    }
docs: Opens an environment with a single default database in 0664 mode using the
  {@link ByteBufferProxy#PROXY_OPTIMAL}.
  
  @param path  file system destination
  @param size  size in megabytes
  @param flags the flags for this new environment
  @return env the environment (never null)