Remove k digits - shortened

RemoveKDigits.java

public static String removeKdigits(String num, int k) {
        Deque<Character> resultDeque = new ArrayDeque<>();
        resultDeque.add(num.charAt(0));
        for (int i = 1; i < num.length(); ++i) {
            var nextChar = num.charAt(i);
            while (k > 0 && !resultDeque.isEmpty() && resultDeque.peekLast() > nextChar) { //Возвращаемся на символ назад
                resultDeque.removeLast();
                k--;
            }
            resultDeque.add(nextChar);
        }
        while (k > 0) {
            resultDeque.removeLast();
            k--;
        }
        StringBuilder builder = new StringBuilder();
        while (!resultDeque.isEmpty()) {
            char ch = resultDeque.removeFirst();
            if (builder.length() == 0 && ch == '0') {
                continue;
            }
            builder.append(ch);
        }
        return builder.length() == 0 ? "0" : builder.toString();
    }