if (chars.length() == 1) { return new CharMatcher(chars.charAt(0));
if (chars.length == 1) { return new CharMatcher(chars[0]);
    public static StrMatcher charSetMatcher(String chars) {        if (chars == null || chars.length() == 0) {            return NONE_MATCHER;        }        if (chars.length() == 1) {            return new CharMatcher(chars.charAt(0));        }        return new CharSetMatcher(chars.toCharArray());    }