code: private String getSentenceFromTokens(final String[] tokens) {
      final StringBuilder sb = new StringBuilder();
      for (final String token : tokens) {
        sb.append(token).append(" ");
      }
      final String sentence = sb.toString();
      return sentence;
    }
docs: It takes an array of tokens and outputs a string with tokens joined by a
  whitespace.
  
  @param array
  of tokens
  @return string representing one sentence for each array