code: public static String ptb2Text(String ptbText) {
      StringBuilder sb = new StringBuilder(ptbText.length()); // probably an overestimate
      PTB2TextLexer lexer = new PTB2TextLexer(new StringReader(ptbText));
      try {
        for (String token; (token = lexer.next()) != null; ) {
          sb.append(token);
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
      return sb.toString();
    }
docs: Returns a presentable version of the given PTB-tokenized text.
  PTB tokenization splits up punctuation and does various other things
  that makes simply joining the tokens with spaces look bad. So join
  the tokens with space and run it through this method to produce nice
  looking text. It's not perfect, but it works pretty well.
  
  @param ptbText A String in PTB3-escaped form
  @return An approximation to the original String