不用StringBuilder,不用reverse,直接倒叙开炮

import java.util.Scanner;

/**
 * @author Fanqingle
 * Created by Administrator on 2022-05-06 03:55
 */
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String a = sc.nextLine();
        for (int i = a.length() - 1; i >= 0; i--) {
            System.out.print(a.charAt(i));
        }
    }
}