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