class PatternUtil {
    private PatternUtil() {
        // private to enforce static
    }

    /**
     * A check if a pattern contains at least one pair of parentheses meaning
     * that there is at least one capture group. This group must not be empty.
     */
    private static final String PATTERN_SINGLE_GROUP = ".*\\([^\\)]+\\).*";
    /**
     * Error string for invalid patterns without a single group. This is passed
     * as a first argument to the constructor of PatternSyntaxException and in
     * the output it is followed by the invalid pattern.
     *
     * @see PatternSyntaxException
     * @see #PATTERN_SINGLE_GROUP
     */
    private static final String PATTERN_MUST_CONTAIN_GROUP = "The pattern must contain at least one non-empty group -";

    /**
     * Check and compile the bug pattern.
     *
     * @param pattern the new pattern
     * @throws PatternSyntaxException when the pattern is not a valid regexp or
     * does not contain at least one capture group and the group does not
     * contain a single character
     */
    public static String compilePattern(String pattern) throws PatternSyntaxException {<FILL_FUNCTION_BODY>}
}

        if (!pattern.matches(PATTERN_SINGLE_GROUP)) {
            throw new PatternSyntaxException(PATTERN_MUST_CONTAIN_GROUP, pattern, 0);
        }
        return Pattern.compile(pattern).toString();
    
<no_super_class>