题解 | #【模板】栈#

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class Main{
     public static void main(String [] arg){
        Scanner sc = new Scanner(System.in);
        MyStatck statck = new MyStatck();
        while(sc.hasNextLine()){
            String tmpStr= sc.nextLine();
            String [] tempArr= tmpStr.split(" ");
            if("push".equals(tempArr[0])){
                statck.push(Integer.valueOf(tempArr[1]));
                continue;
            }  
            if("pop".equals(tempArr[0])){
                statck.pop();
                continue;
            }
            if("top".equals(tempArr[0])){
                statck.top();
            }
            
        }
    }
}
class MyStatck{
    List<Integer> data;
 
    public MyStatck(){
        data =new ArrayList();
    }
    
    public void push(int value){
       data.add(value);
    }
    
    public void pop(){
        if(data.isEmpty()){
           System.out.println("error");
           return;
        }
         int index= data.size()-1;
         System.out.println(data.get(index));
         data.remove(index);   
    }
    
    public void top(){
        if(data.isEmpty()){
            System.out.println("error");
            return;
        }
        System.out.println(data.get(data.size()-1)); 
    }
}