/**
     * creates an new empty object and adds it to the current list. The new child object becomes the
     * active one.
     * 
     * @return returns itself so you can chain
     */
    public BasicDBObjectBuilder addToList()
    {
        DBObject list = _cur();
        if (!(list instanceof BasicDBList)) {
            throw new IllegalStateException("addToList without pushList");
        }
        BasicDBObject o = new BasicDBObject();
        ((BasicDBList) list).add(o);
        _stack.addLast(o);
        return this;
    }

    /**
     * adds the given val to the current list. The passed value does NOT become the new active
     * object even if it's a DBObject
     * 
     * @param val the value to be added to the list
     * @return returns itself so you can chain
     */
    public BasicDBObjectBuilder addToList(Object val)
    {
        DBObject list = _cur();
        if (!(list instanceof BasicDBList)) {
            throw new IllegalStateException("addToList without pushList");
        }
        ((BasicDBList) list).add(val);
        return this;
    }

    /**
     * creates an new empty list and inserts it into the current object with the given key. The new
     * list becomes the active one. You can use either {@link #push(String)},
     * {@link #pushList(String)}, {@link #addToList()} or {@link #addToList(Object)} to add elements
     * to the list. When using {@link #push(String)} or {@link #pushList(String)} the key is the
     * index of the value to be inserted. For instance push("3") would add the new object at the 4th
     * position in the list.
     *
     * @param key
     * @return returns itself so you can chain
     */
    public BasicDBObjectBuilder pushList(String key)
    {
        BasicDBList list = new BasicDBList();
        _cur().put(key, list);
        _stack.addLast(list);
        return this;
    }