class Glob {

    private static final String REGEX_META_CHARS = ".^$+{[]|()";
    private static final String GLOB_META_CHARS = "\\*?[{";

    /**
     * Creates a regex pattern from the given glob expression.
     *
     * @param globPattern the given glob expression
     * @return the regex pattern
     */
    public static String toRegexPattern(String globPattern) {<FILL_FUNCTION_BODY>}

    private static boolean isRegexMeta(char c) {
        return REGEX_META_CHARS.indexOf(c) != -1;
    }

    private static boolean isGlobMeta(char c) {
        return GLOB_META_CHARS.indexOf(c) != -1;
    }

    private static char next(String glob, int i) {
        return i < glob.length() ? glob.charAt(i) : 0;
    }
}

        boolean inGroup = false;
        StringBuilder regex = new StringBuilder("^");

        int i = 0;
        while (i < globPattern.length()) {
            char c = globPattern.charAt(i++);
            switch (c) {
                case '\\':
                    // escape special characters
                    if (i == globPattern.length()) {
                        throw new PatternSyntaxException("No character to escape",
                            globPattern, i - 1);
                    }
                    char next = globPattern.charAt(i++);
                    if (isGlobMeta(next) || isRegexMeta(next)) {
                        regex.append('\\');
                    }
                    regex.append(next);
                    break;
                case '/':
                    regex.append(c);
                    break;
                case '[':
                    // don't match name separator in class
                    regex.append("[[^/]&&[");
                    if (next(globPattern, i) == '^') {
                        // escape the regex negation char if it appears
                        regex.append("\\^");
                        i++;
                    } else {
                        // negation
                        if (next(globPattern, i) == '!') {
                            regex.append('^');
                            i++;
                        }
                        // hyphen allowed at start
                        if (next(globPattern, i) == '-') {
                            regex.append('-');
                            i++;
                        }
                    }
                    boolean hasRangeStart = false;
                    char last = 0;
                    while (i < globPattern.length()) {
                        c = globPattern.charAt(i++);
                        if (c == ']') {
                            break;
                        }
                        if (c == '/') {
                            throw new PatternSyntaxException("Explicit 'name separator' in class",
                                globPattern, i - 1);
                        }
                        // TBD: how to specify ']' in a class?
                        if (c == '\\' || c == '[' || c == '&' && next(globPattern, i) == '&') {
                            // escape '\', '[' or "&&" for regex class
                            regex.append('\\');
                        }
                        regex.append(c);

                        if (c == '-') {
                            if (!hasRangeStart) {
                                throw new PatternSyntaxException("Invalid range",
                                    globPattern, i - 1);
                            }
                            if ((c = next(globPattern, i++)) == 0 || c == ']') {
                                break;
                            }
                            if (c < last) {
                                throw new PatternSyntaxException("Invalid range",
                                    globPattern, i - 3);
                            }
                            regex.append(c);
                            hasRangeStart = false;
                        } else {
                            hasRangeStart = true;
                            last = c;
                        }
                    }
                    if (c != ']') {
                        throw new PatternSyntaxException("Missing ']", globPattern, i - 1);
                    }
                    regex.append("]]");
                    break;
                case '{':
                    if (inGroup) {
                        throw new PatternSyntaxException("Cannot nest groups",
                            globPattern, i - 1);
                    }
                    regex.append("(?:(?:");
                    inGroup = true;
                    break;
                case '}':
                    if (inGroup) {
                        regex.append("))");
                        inGroup = false;
                    } else {
                        regex.append('}');
                    }
                    break;
                case ',':
                    if (inGroup) {
                        regex.append(")|(?:");
                    } else {
                        regex.append(',');
                    }
                    break;
                case '*':
                    if (next(globPattern, i) == '*') {
                        // crosses directory boundaries
                        regex.append(".*");
                        i++;
                    } else {
                        // within directory boundary
                        regex.append("[^/]*");
                    }
                    break;
                case '?':
                    regex.append("[^/]");
                    break;

                default:
                    if (isRegexMeta(c)) {
                        regex.append('\\');
                    }
                    regex.append(c);
            }
        }

        if (inGroup) {
            throw new PatternSyntaxException("Missing '}", globPattern, i - 1);
        }

        return regex.append('$').toString();
    
<no_super_class>