백준 10828번 (스택)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import java.util.*;

import static java.util.Collections.*;

public class Main {
public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

   int N = Integer.parseInt(br.readLine());

   Stack<Integer> stack = new Stack<>();

    for (int i = 0 ; i < N; i++)
   {
       String line = br.readLine();

       String[] parts = line.split(" ");

       if (parts[0].equals("push"))
       {
           stack.push(Integer.parseInt(parts[1]));
       }

       if (parts[0].equals("top"))
       {
           if (stack.isEmpty())
           {
               System.out.println(-1);
               continue;
           }
           System.out.println(stack.peek());
       }

       if (parts[0].equals("size"))
       {
           System.out.println(stack.size());
       }

       if (parts[0].equals("empty"))
       {
           if (stack.isEmpty())
           {
               System.out.println(1);
           }
           else{
               System.out.println(0);
           }
       }
       if (parts[0].equals("pop"))
       {
           if (stack.isEmpty())
           {
               System.out.println(-1);
               continue;
           }

           System.out.println(stack.peek());
           stack.pop();
       }




   }









}
}

스택 문제 복기하기로는 좋았다.