Collector interpretation and custom

A, Collector Interface interpretation:　　　　　　

Collector Interface Interpretation:

1 public interface Collector<T, A, R> {
2     Supplier<A> supplier();
3     BiConsumer<A, T> accumulator();
4     BinaryOperator<A> combiner();
5     Function<A, R> finisher();
6     Set<Characteristics> characteristics();
7 }

Collector <T, A, R & lt>
T: the element type stream;
A: type accumulator, can be thought of a container. To accumulate such as T, into List <T>, A type is List.
R: Final Return Value Type
T IS The Generic type of The items in The Stream to BE Collected.
A IS The type of The ACC with, The Object ON Which The partial Result Will BE Accumulated During The Collection Process.
R & lt IS The type of The object (typically, but not always, the collection) resulting from the collect operation.

 

Second, Custom Collector, to see how to achieve