code: @Nonnull
    public static FileIOError createDir (@Nonnull final Path aDir)
    {
      ValueEnforcer.notNull (aDir, "Directory");
  
      final Path aRealDir = _getUnifiedPath (aDir);
      return FileOperations.createDir (aRealDir.toFile ());
  
      // // Does the directory already exist?
      // if (Files.exists (aRealDir))
      // return EFileIOErrorCode.TARGET_ALREADY_EXISTS.getAsIOError
      // (EFileIOOperation.CREATE_DIR, aRealDir);
      //
      // // Is the parent directory writable?
      // final Path aParentDir = aRealDir.getParent ();
      // if (aParentDir != null && Files.exists (aParentDir) && !Files.isWritable
      // (aParentDir))
      // return EFileIOErrorCode.SOURCE_PARENT_NOT_WRITABLE.getAsIOError
      // (EFileIOOperation.CREATE_DIR, aRealDir);
      //
      // return _perform (EFileIOOperation.CREATE_DIR, Files::createDirectory,
      // aRealDir);
    }
docs: Create a new directory. The direct parent directory already needs to exist.
  
  @param aDir
  The directory to be created. May not be <code>null</code>.
  @return A non-<code>null</code> error code.