title: The method flatMapping((<no type> dish) -> {}, toSet()) is undefined for the type Grouping
body: <p>I am using Java 8 and getting below error for the code on line-30</p>
  
  <blockquote>
    <p>The method flatMapping(( dish) -> {}, toSet()) is undefined for the type Grouping</p>
  </blockquote>
  
  <pre><code>public class Grouping {
      enum CaloricLevel { DIET, NORMAL, FAT };
  
      public static void main(String[] args) {
          System.out.println("Dishes grouped by type: " + groupDishesByType());
          System.out.println("Dish names grouped by type: " + groupDishNamesByType());
          System.out.println("Dish tags grouped by type: " + groupDishTagsByType());
      }
  
  
      private static Map&lt;Type, List&lt;Dish&gt;&gt; groupDishesByType() {
          return Dish.menu.stream().collect(groupingBy(Dish::getType));
      }
  
      private static Map&lt;Type, List&lt;String&gt;&gt; groupDishNamesByType() {
          return Dish.menu.stream().collect(groupingBy(Dish::getType, mapping(Dish::getName, toList())));
      }
  
  
      private static String groupDishTagsByType() {
  /*line:30*/ return menu.stream().collect(groupingBy(Dish::getType, flatMapping(dish -&gt; dishTags.get( dish.getName() ).stream(), toSet())));
      }
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/aCPXI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aCPXI.png" alt="enter image description here"></a></p>