Java efficient string formatter

/**
 * Similar to {@link java.text.MessageFormat#format(String, Object...)}, only more efficient, and
 * escaping a bracket char is done with the <code>\</code> char, instead of the <code>'</code> char
 * <p>
 *     Malformed formats will be worked around, and no exceptions will be thrown
 * </p>
 * @param format The value to be formatted
 * @param args   The values to splice in
 * @return A string where all of the {...} cases have been replaced with the given arguments
 * @author REghZy/BrakeJetz
 */
public static String format(@Nullable String format, Object... args) {
    int i, j = 0, k, n;
    if (StringUtils.isEmpty(format) || (i = format.indexOf('{')) == -1)
        return format;
    StringBuilder sb = new StringBuilder(format.length() * 2); // buffer of 2x format is typically the best result
    do {
        if (i == 0 || format.charAt(i - 1) != '\\') { // check escape char
            sb.append(format, j, i); // append text between j and before '{' char
            if ((k = format.indexOf('}', i)) != -1) { // get closing char index
                j = k + 1; // set last char to after closing char
                if (Parsing.parseInt(format, i + 1, k) && (n = Parsing.getInt()) >= 0 && n < args.length) {
                    sb.append(args[n]); // append content
                }
                else {
                    // append content between '{' and '}' with the brackets too
                    sb.append('{').append(format, i + 1, k).append('}');
                }
                i = j - 1; // set next search index to j (sub 1 because 1 will be added to i next search)
            }
            else {
                j = i; // set last char to the last '{' char
            }
        }
        else { // remove escape char
            sb.append(format, j, i - 1); // append text between j and before the escape char
            j = i; // set last index to the '{' char, which was originally escaped
        }
    } while ((i = format.indexOf('{', i + 1)) != -1);
    if (j < format.length()) // append remainder of string
        sb.append(format, j, format.length());
    return sb.toString();
}