package com.coding.basic;
public class Stack {
private ArrayList al = null;
public Stack(){
al = new ArrayList();
}
public void push(Object o){
al.add(o);
}
public Object pop(){
return al.remove(al.size()-1);
}
public Object peek(){
return (al.size() == 0) ? null : al.get(al.size() -1);
}
public boolean isEmpty(){
return (al.size() == 0) ? true : false;
}
public int size(){
return al.size();
}
}