void advance() {
			if (index == 0) {
				previous = -1;
				current = chars.charAt(0);
				next = 1 < chars.length() ? chars.charAt(1) : -1;
				++index;
			} else {
				previous = current;
				current = (char)next;
				++index;
				next = index < chars.length() ? chars.charAt(index) : -1;
			}
		}
Joins the given CSV {@code columns}, using the given separator and
quote character.

@param columns the CSV columns to join
@return the joined CSV columns
jenetics.ext/src/main/java/io/jenetics/ext/util/CsvSupport.java