docs: public static String join(Iterable<?> objects, String separator)
    {
      if(objects == null) {
        return null;
      }
      if(separator == null) {
        separator = " ";
      }
  
      StringBuilder builder = new StringBuilder();
      boolean first = true;
      for(Object object : objects) {
        if(object == null) {
          continue;
        }
        String value = object instanceof String ? (String)object : object.toString();
        if(value.isEmpty()) {
          continue;
        }
        if(first) {
          first = false;
        }
        else {
          builder.append(separator);
        }
        builder.append(value);
      }
      return builder.toString();
    }