利用StringBuilder进行字符逆序排列,再利用toString()转化为字符串

import java.util.*;
public class Main{
    public static void main(String args[]){
        Scanner sc=new Scanner(System.in);
        while(sc.hasNextInt()){
            int n=sc.nextInt();
            StringBuilder sb=new StringBuilder();
            sb.append(n);
            System.out.println(sb.reverse().toString());
        }
    }
}