code: private static String parseVersionNumber(String line) {
          StringTokenizer tokenizer = new StringTokenizer(line, " \t");
  
          if (!expect(tokenizer, "sourceInfo") || !expect(tokenizer, "version") || !tokenizer.hasMoreTokens()) {
              return null;
          }
  
          return tokenizer.nextToken();
      }
docs: Parse the sourceInfo version string.
  
  @param line
  the first line of the sourceInfo file
  @return the version number constant, or null if the line does not appear
  to be a version string