package com.github.Ven13.coding2017.basic;
public class Stack {
private ArrayList elementData = new ArrayList();
public void push(Object o){
elementData.add(o);
}
public Object pop(){
Object o = null;
if(elementData.size() > 0) {
o = elementData.get(elementData.size() - 1);
elementData.remove(elementData.size() - 1);
}
return o;
}
public Object peek(){
return elementData.get(0);
}
public boolean isEmpty(){
return elementData.size() == 0;
}
public int size(){
return elementData.size();
}
}