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