Java Coding Problems

filtering()

User problem: I want to take all the melons that are heavier than 2,000 g and group them by their type. For each type, add them to the proper container (there is a container for each type – just check the container's labels).

By using filtering​(Predicate<? super T> predicate, Collector<? super T,​A,​R> downstream), we apply a predicate to each element of the current collector and accumulate the output in the downstream collector.

So, to group the melons that are heavier than 2,000 g by type, we can write the following stream pipeline:

Map<String, Set<Melon>> melonsFiltering = melons.stream()  .collect(groupingBy(Melon::getType,    filtering(m -> m.getWeight() > 2000, toSet())));

The output will be as follows (each Set<Melon> is a ...