Introduction to Programming

Class collectors

The java.util.stream.Collectors class provides more than 40 methods that create Collector objects. We are going to demonstrate only the simplest and  most popular ones:

• Collector<T,?,List<T>> toList(): Creates a collector that collects the stream elements into a List object.
• Collector<T,?,Set<T>> toSet(): Creates a collector that collects the stream elements into a Set object.
• Collector<T,?,Map<K,U>> toMap (Function<T,K> keyMapper, Function<T,U> valueMapper): Creates a collector that collects the stream elements into a Map object.
• Collector<T,?,C> toCollection (Supplier<C> collectionFactory): Creates a collector that collects the stream elements into a Collection object of the type specified by the collection factory.