@Nullable public static String md5(@Nullable File file,@Nullable IgniteLogger log){
  if (file != null)   return file.isFile() ? fileMd5(file,log) : directoryMd5(file,log);
  return null;
}

@ Nullable public static String md5 ( @ Nullable File file , @ Nullable IgniteLogger log ) { if ( file != null ) return file . isFile ( ) ? fileMd5 ( file , log ) : directoryMd5 ( file , log ) ; return null ; }
calculates md5 checksum for the given file o directory . for directories tries to walk all nested files accumulating the result .
