code: String stringJoinAndDecorate(final List<String> list, final String sep, StringDecorator decorator) {
  		if (decorator == null) {
  			decorator = new NothingDecorator();
  		}
  		StringBuilder sb = new StringBuilder();
  		if (list != null) {
  			boolean first = true;
  			for (String argument : list) {
  				if (!first) {
  					sb.append(sep);
  				}
  				sb.append(decorator.decorate(argument));
  				first = false;
  			}
  		}
  		return sb.toString();
  	}
docs: Join list and separate by sep, each elements is decorate by 'decorator'
  
  @param list
  @param decoration
  @return