Satcks & Queues _8. Simple Text Editor

import java.util.ArrayDeque;
import java.util.Scanner;

public class Ex08_SimpleTextEditor {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int countCommands = Integer.parseInt(scanner.nextLine());

        ArrayDeque<String> commands = new ArrayDeque<>();
        ArrayDeque<Character> text = new ArrayDeque<>();
        ArrayDeque<Character> erasedChars = new ArrayDeque<>();

        for (int i = 0; i < countCommands; i++) {
            String command = scanner.nextLine();
            if (command.charAt(0) != '3' && command.charAt(0) != '4') {
                commands.push(command);
            }
            String[] tokens = command.split("\\s+");
            int action = Integer.parseInt(tokens[0]);


            switch (action) {
                case 1:
                    String element = tokens[1];
                    for (int j = 0; j < element.length(); j++) {
                        text.push(element.charAt(j));
                    }
                    break;
                case 2:
                    int countCharsToErase = Integer.parseInt(tokens[1]);
                    for (int k = 0; k < countCharsToErase; k++) {
                        char curr = text.pop();
                        erasedChars.offer(curr);
                    }
                    break;
                case 3:
                    System.out.println(text.peek());
                    break;
                case 4:
                    String undoCommand = commands.pop();
                    if (undoCommand.charAt(0) == '1') {
                        element = undoCommand.substring(2);
                        for (int j = 0; j < element.length(); j++) {
                            text.pop();
                        }

                    } else if (undoCommand.charAt(0) == '2') {
                        int reinstateCharsCount = Character.getNumericValue(undoCommand.charAt(2));
                        if (erasedChars.size() >= reinstateCharsCount) {
                            for (int l = 0; l < reinstateCharsCount; l++) {
                                char toReinstate = erasedChars.poll();
                                text.push(toReinstate);
                            }
                        }

                    }
                    break;
            }

        }

    }
}