问链表栈

EN

public class ArrayListStack<E> implements Stack<E> {

    private ArrayList<E> list;

    public ArrayListStack()
    {
        list = new ArrayList<>();
    }

    public int size()
    {
        return list.size();
    }

    public boolean isEmpty()
    {
        return size() == 0;
    }

    public void push(E e)
    {
        list.add(size(), e);
    }

    public E top()
    {
        if(isEmpty()) throw new IllegalStateException("Array is empty");
        return list.get(size()-1);
    }

    public E pop()
    {
        if(isEmpty()) throw new IllegalStateException("Array is empty");
        return list.remove(size()-1);
    }


}