package com.coding.datastructs;
public class Stack {
private ArrayList elementData = new ArrayList();
public void push(Object o){
elementData.add(o);
}
public Object pop(){
if (elementData.size()<=0) {
throw new NullPointerException("Stack���������ݣ����ܽ���ɾ������");
}
Object data = elementData.get(elementData.size()-1);
elementData.remove(size()-1);
return data;
}
public Object peek(){
Object data = elementData.get(elementData.size()-1);
return data;
}
public boolean isEmpty(){
if(elementData.size()>0){
return false;
}else{
return false;
}
}
public int size(){
return elementData.size();
}
}