O3. Take Skip Rope / Lists - More Exercise

package ListsMoreExercise;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class O3TakeSkipRope {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        String input = scanner.nextLine();
        List<Integer> numbers = new ArrayList<>();
        List<Character> characters = new ArrayList<>();

        for (int i = 0; i < input.length(); i++) {
            char index = input.charAt(i);

            if (input.charAt(i) >= 48 && input.charAt(i) <= 57) {
                numbers.add(Integer.parseInt(String.valueOf(index)));
            } else {
                characters.add(input.charAt(i));
            }
        }

        List<Integer> take = new ArrayList<>();
        List<Integer> skip = new ArrayList<>();

        for (int i = 0; i < numbers.size(); i++) {
            if (i % 2 == 0) {
                take.add(numbers.get(i));
            } else {
                skip.add(numbers.get(i));
            }
        }

        StringBuilder hiddenMessage = new StringBuilder();

        for (int i = 0; i < numbers.size() / 2; i++) {

            int takeIndex = take.get(i);
            for (int j = 0; j < takeIndex; j++) {
                if (characters.size() == 0) {
                    break;
                }
                hiddenMessage.append(characters.get(0));
                characters.remove(0);
            }
            int skipIndex = skip.get(i);
            if (skipIndex > 0) {
                if (characters.size() == 0) {
                    break;
                }
                characters.subList(0, skipIndex).clear();
            }
        }
        System.out.println(hiddenMessage);
    }
}