get size of collection in nested hashmap? : <p>I have data structure of type <code>Map&lt;String, Map &lt;String, List&lt;ExciseReportDataPoint&gt;&gt;&gt; Data</code> I would like to calculate number of entries in <code>List&lt;ExciseReportDataPoint&gt;</code> for each top level key.</p>

<p>We can think about the hashmap in logical manner as <code>Map&lt;LiquorCategory, Map&lt;LiquorBrand, List&lt;LiquorBottles&gt;&gt;&gt;</code>. Basically I want to know how many liquor bottles for each LiquorCategory.</p>
