code: public static String join(String separator, Collection<String> values) {
  		StringBuilder builder = new StringBuilder();
  		boolean first = true;
  
  		for (String value : values) {
  			if (!first) {
  				builder.append(separator);
  			}
  
  			builder.append(value);
  			first = false;
  		}
  
  		return builder.toString();
  	}
docs: Join all strings to a single one using given separator.
  
  @param separator String separator.
  @param values All string to join.
  @return The final string.