package com.list;
import java.util.ArrayList;
import java.util.EmptyStackException;
public class Stack {
ArrayList<Object> elelmentData = new ArrayList<Object>();
//压入栈
public void push(Object object){
elelmentData.add(object);
}
//弹出栈
public Object pop(){
if (isEmpty()){ throw new EmptyStackException();}
return elelmentData.remove(elelmentData.size() - 1);
}
//取栈顶元素
public Object peek(){
if (isEmpty()){return null;}
return elelmentData.get(elelmentData.size() - 1);
}
public boolean isEmpty(){
return elelmentData.isEmpty();
}
public int size(){
if (isEmpty()){throw new EmptyStackException();}
return elelmentData.size();
}
}