TextEditor

package StacksAndQueues;

import java.util.Scanner;
import java.util.Stack;

public class SimpleTextEditor {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        Stack<StringBuilder> datas = new Stack<>();

        int n = sc.nextInt();
        sc.nextLine();

        for (int i = 0; i < n; i++) {
            int command = sc.nextInt();
            StringBuilder sb = new StringBuilder();

            switch (command) {
                case 1:
                    String input = sc.nextLine().trim();
                    if (!datas.isEmpty()) {
                        datas.push(datas.peek().append(input));
                    } else {
                        datas.push(sb.append(input));
                    }
                    break;
                case 2:
                    sb.append(datas.peek());
                    sb.delete(sb.length() - sc.nextInt(), sb.length());
                    datas.push(sb);
                    break;
                case 3:
                    sb.append(datas.peek());
                    System.out.println(sb.charAt(sc.nextInt() - 1));
                    break;
                case 4:
                    datas.pop();
                    break;
            }
        }
    }
}