public static String expand(final char a, final char b) {
		final StringBuilder out = new StringBuilder();

		if (a < b) {
			char c = a;
			while (c <= b) {
				out.append(c);
				c = (char) (c + 1);
			}
		} else if (a > b) {
			char c = a;
			while (c >= b) {
				out.append(c);
				c = (char)(c - 1);
			}
		}

		return out.toString();
	}
Expands the characters between {@code a} and {@code b}.

@param a the start character.
@param b the stop character.
@return the expanded characters.
jenetics/src/main/java/io/jenetics/util/CharSeq.java