title: Using Java 8 streams groupingBy on a list of list of Strings?
body: <p>I have the following list of strings</p>
  
  <pre><code>List&lt;String&gt; product_a= Arrays.asList("Product A", "Category A", "Price");
  List&lt;String&gt; product_b= Arrays.asList("Product A", "Category A", "Price");
  List&lt;String&gt; product_c= Arrays.asList("Product B", "Category B", "Price");
  List&lt;String&gt; product_d = Arrays.asList("Product C", "Category C", "Price");
  </code></pre>
  
  <p>Then, I put them in another list</p>
  
  <pre><code>List&lt;List&lt;String&gt;&gt; products = new ArrayList&lt;&gt;();
  products.add(product_a);
  products.add(product_b);
  products.add(product_c);
  products.add(product_d);
  </code></pre>
  
  <p>Using streams, Collectors.groupingBy, Collectors.counting, how can I get the following output? is it possible?</p>
  
  <pre><code>Product A - 2
  Product B - 1
  Product C - 1
  </code></pre>
  
  <p>In advance, thank you for your help.</p>