백준 10828 : 스택 자바 java

https://www.acmicpc.net/problem/10828

10828번: 스택

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import java.io.*;
import java.util.*;

public class Main {

	
	static Stack<Integer> st = new Stack<>();
    public static void main(String[] args) throws IOException{
    	
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	int num = Integer.parseInt(br.readLine());
    	
    	for(int i=0;i<num;i++) {
    		String str=br.readLine();
    		chevkVps(str);
    	}  	
    	
    }
    
    public static void chevkVps(String str) {
    	if(str.contains("push")) {
    		StringTokenizer tk = new StringTokenizer(str," ");
    		tk.nextToken();
    		int pushNum=Integer.parseInt(tk.nextToken());
    		st.add(pushNum);
    	}else if(str.equals("top")) {
    		if(st.empty())	System.out.println(-1);
    		else 	System.out.println(st.peek());
    	}else if(str.equals("size")) {
    		System.out.println(st.size());
    	}else if(str.equals("pop")) {
    		if(st.empty())	System.out.println(-1);
    		else {
    			System.out.println(st.peek());
    			st.pop();
    			}

    	}else if(str.equals("empty")) {
    		if(st.empty())	System.out.println(1);
    		else 	System.out.println(0);
    	}
    }
}