[64] ArrayList 로 Stack 구현

package collection;

import java.util.ArrayList;

class MyStack {

	ArrayList <String> stack = new ArrayList<String>();
	
	public void push() {
		stack.add("안녕");
	}
	
	public String pop() {
		int len = stack.size();
		if(len == 0) {
			System.out.println("스택이 비었습니다.");
			return null;
		} else {
			return stack.remove(len-1); // 마지막 에 넣은 값 뺴낸다.
		}
	}
}
public class StackTest {	
		public static void main(String[] args) {
			MyStack stacklist = new MyStack();
			
			stacklist.push();
			stacklist.push();
			stacklist.push();
			
			System.out.println(stacklist.pop());
			System.out.println(stacklist.pop());
			System.out.println(stacklist.pop());
			System.out.println(stacklist.pop());
			System.out.println(stacklist.pop());
		
	}
}