题解 | #数字颠倒# stack

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

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String inputNum = in.nextLine();
        System.out.println(reverseStr(inputNum));
    }

    private static String reverseStr(String str) {
        if (str.length() == 0 || str.length() == 1) {
            return str;
        }
        Stack<Character> stack = new Stack<Character>();
        int i = 0;
        for (char c : str.toCharArray()) {
            stack.push(str.charAt(i));
            i++;
        }
        String result = "";
        while(!stack.isEmpty()) {
            result = result + stack.pop().toString();
        }
        return result;
    }
}