Java SE 8+ STREAM: peek() vs. forEach() etc.

Sources:

https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html

https://www.baeldung.com/java-streams-peek-api

https://programuj.pl/blog/java8-strumienie-cz3-peek-map-collect

<R,A> R	collect(Collector<? super T,A,R> collector) Performs a mutable reduction operation on the elements of this stream using a Collector.
<R> R	collect(Supplier<R> supplier, BiConsumer<R,? super T> accumulator, BiConsumer<R,R> combiner) Performs a mutable reduction operation on the elements of this stream.

Stream<T>

filter(Predicate<? super T> predicate) Returns a stream consisting of the elements of this stream that match the given predicate.

static <T> Stream<T>	generate(Supplier<T> s) Returns an infinite sequential unordered stream where each element is generated by the provided Supplier.
static <T> Stream<T>	iterate(T seed, UnaryOperator<T> f) Returns an infinite sequential ordered Stream produced by iterative application of a function f to an initial element seed, producing a Stream consisting of seed, f(seed), f(f(seed)), etc.
Stream<T>	limit(long maxSize) Returns a stream consisting of the elements of this stream, truncated to be no longer than maxSize in length.
<R> Stream<R>	map(Function<? super T,? extends R> mapper) Returns a stream consisting of the results of applying the given function to the elements of this stream.

static <T> Stream<T>	of(T... values) Returns a sequential ordered stream whose elements are the specified values.
static <T> Stream<T>	of(T t) Returns a sequential Stream containing a single element.

Optional<T>	reduce(BinaryOperator<T> accumulator) Performs a reduction on the elements of this stream, using an associative accumulation function, and returns an Optional describing the reduced value, if any.
T	reduce(T identity, BinaryOperator<T> accumulator) Performs a reduction on the elements of this stream, using the provided identity value and an associative accumulation function, and returns the reduced value.
<U> U	reduce(U identity, BiFunction<U,? super T,U> accumulator, BinaryOperator<U> combiner) Performs a reduction on the elements of this stream, using the provided identity, accumulation and combining functions.

<R> Stream<R>

flatMap(Function<? super T,? extends Stream<? extends R>> mapper) Returns a stream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element.

void	forEach(Consumer<? super T> action) Performs an action for each element of this stream.

Stream<T>

peek(Consumer<? super T> action) Returns a stream consisting of the elements of this stream, additionally performing the provided action on each element as elements are consumed from the resulting stream.