Java Coding Problems

191. Filtering, flattening, and mapping collectors

Let's assume that we have the following Melon class and List of Melon:

public class Melon {  private final String type;  private final int weight;  private final List<String> pests;  // constructors, getters, setters, equals(),  // hashCode(), toString() omitted for brevity}List<Melon> melons = Arrays.asList(new Melon("Crenshaw", 2000),  new Melon("Hemi", 1600), new Melon("Gac", 3000),  new Melon("Hemi", 2000), new Melon("Crenshaw", 1700),  new Melon("Gac", 3000), new Melon("Hemi", 2600));

The Java Stream API provides filtering(), flatMapping(), and mapping(), especially for use in multi-level reductions (such as the downstream of groupingBy() or partitioningBy()).

Conceptually, the goal of filtering() ...