如何访问地图内的ArrayList？

So i have a data structure:

所以我有一个数据结构:

Map<String, Map<String, ArrayList<Double>>> dataStructure = new HashMap<String, Map<String, ArrayList<Double>>>();

if(!dataStructure.containsKey(key)) {
                dataStruct2.put(key, new HashMap<String, ArrayList<Double>>());
        }
Ma