换成数组直接逆序输出就行

import java.util.*;

public class Main{
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        String[] str = sc.nextLine().split(" ");
        for (int i = str.length - 1;i >= 0 ; i--) {
            System.out.print(str[i] + " ");
        }
    }
}