code: public static long getZxidFromName(String name, String prefix) {
          long zxid = -1;
          String nameParts[] = name.split("\\.");
          if (nameParts.length == 2 && nameParts[0].equals(prefix)) {
              try {
                  zxid = Long.parseLong(nameParts[1], 16);
              } catch (NumberFormatException e) {
              }
          }
          return zxid;
      }
docs: Extracts zxid from the file name. The file name should have been created
  using one of the {@link makeLogName} or {@link makeSnapshotName}.
  
  @param name the file name to parse
  @param prefix the file name prefix (snapshot or log)
  @return zxid