question: private static String dirName ( String nodeName ) { for ( int i = 0 , n = nodeName . length ( ) ; i < n ; i ++ ) if ( ! isDirChar ( nodeName . charAt ( i ) ) ) return "_" + Base64 . byteArrayToAltBase64 ( byteArray ( nodeName ) ) ; return nodeName ; }
target:  Returns the directory name corresponding to the specified node name. Generally, this is just the node name.  If the node name includes inappropriate characters (as per isDirChar) it is translated to Base64. with the underscore  character ('_', 0x5f) prepended.