题解 | #数字颠倒#

直接不经思考反向输出

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String strings = in.nextLine();
        int length = strings.length();
        // 直接反向输出
        for(int i = length - 1; i >= 0; i--) {
            System.out.print(strings.charAt(i));
        }
    }
}

还可以使用栈结构

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String strings = in.nextLine();
        int length = strings.length();
        Stack<Character> stack = new Stack<Character>();
        // 第一遍压栈
        for(int i = 0; i < length; i++) {
            char c = strings.charAt(i);
            stack.push(c);
        }
        // 第二遍弹栈
        for(int i = 0; i< length; i ++) {
            System.out.print(stack.pop());
        }
    }
}