题解 | #【模板】栈#

import java.util.Scanner;
import java.util.Stack;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

// 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 scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        Stack<Integer> stack = new Stack<>();

        for (int i = 0; i < n; i++) {
            String operation = scanner.next();
            if (operation.equals("push")) {
                int num = scanner.nextInt();
                stack.push(num);
            } else if (operation.equals("pop")) {
                if (stack.isEmpty()) {
                    System.out.println("error");
                } else {
                    System.out.println(stack.pop());
                }
            } else if (operation.equals("top")) {
                if (stack.isEmpty()) {
                    System.out.println("error");
                } else {
                    System.out.println(stack.peek());
                }
            }
        }
        scanner.close();
    }
}

对于Java语言来说这道题的解题重点更多的是在于对输入的考察