java string interpolation

/**
 * The same as {@link java.text.MessageFormat}'s format() method, only more efficient
 * <p>
 *     Uses a number between {@code {}'s} to index an object in the given arguments. Null objects are handled by the StringBuilder
 * </p>
 * @param value 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
 * @throws BadFormatException If the value between the { and } is empty, or not an integer
 * @throws IndexOutOfBoundsException If the index if out of range (smaller than 0 or bigger than the array's length)
 */
public static String format(String value, Object... args) {
    if (value == null) {
        return null;
    }
    if (value.isEmpty()) {
        return value;
    }
    int firstOpenIndex = value.indexOf('{', 0);
    if (firstOpenIndex == -1) {
        return value;
    }
    char[] chars = value.toCharArray();
    int lastCloseIndex = StringHelper.charsLastIndexOf(chars, '}', firstOpenIndex);
    if (lastCloseIndex == -1) {
        if (firstOpenIndex == 0 || chars[firstOpenIndex - 1] != '\\') { // check if the format is escaped using \\{
            throw new BadFormatException("Initial format check - missing closing '}' after the first opening bracket '{' at index " + firstOpenIndex);
        }
        return value;
    }
    int maxIndex = args.length - 1;
    StringBuilder builder = new StringBuilder(value.length() * 2);
    builder.append(value, 0, firstOpenIndex);
    for (int i = firstOpenIndex, end = chars.length, endIndex = end - 1; i < end; i++) {
        char c = chars[i];
        if (c == '{') {
            // last character
            if (i == endIndex) {
                builder.append(c);
                break;
            }
            // escape
            if (i > 0 && chars[i - 1] == '\\') {
                builder.setCharAt(i - 1, '{');
                continue;
            }
            int nextClose = StringHelper.charsIndexOf(chars, '}', i + 1);
            if (nextClose == -1) {
                throw new BadFormatException("Missing a closing '}' after an opening bracket '{' at index " + i);
                // builder.append(chars, i, chars.length - i - 1);
                // break;
            }
            int parseIndex = i + 1;
            if (parseIndex == nextClose) {
                throw new BadFormatException("Value between '{' and '}' was empty! At index " + parseIndex);
                // builder.append('{');
                // continue;
            }
            Integer index = StringHelper.parseInteger(chars, parseIndex, nextClose);
            if (index == null) {
                throw new BadFormatException("Value between '{' and '}' was not an integer! At index " + parseIndex);
            }
            if (index < 0 || index > maxIndex) {
                throw new IndexOutOfBoundsException("The index (" + index + ") was out of range (array size was " + args.length + ')');
            }
            // let the sb handle null objects :)
            builder.append(args[index]);
            i = nextClose;
        }
        else {
            builder.append(c);
        }
    }
    return builder.toString();
}