스택 클래스 (Stack)

import java.io.*;

class Stack{
	private int stack[];
	int sp = -1;
	Stack(){
		stack = new int[100];
	}
	Stack(int size){
		stack = new int[size];
	}
	public void push(int data) {
		if(stack.length == sp+1)
			System.out.println("스택이 가득 찼습니다.");
		else {
			stack[++sp] = data;
		}
	}
	public int pop() {
		if(sp == -1) {
			System.out.println("스택이 비었습니다.");
			return 0;
		}
		return stack[sp--];
	}
	public int size() {
		return sp;
	}
}
public class chp5_8 {
	public static void main(String[] args) throws java.io.IOException{
		BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
		
		Stack s = new Stack(3);
		int a = -1;
		
		s.pop();
		while(a!=0) {
			a = Integer.parseInt(input.readLine());
			s.push(a);
		}
		
		while(s.size() >= 0)
			System.out.println(s.pop());
	}
}