java.util.stream · java.base · since Java 1.8

Stream

declaration

public interface Stream<T> extends BaseStream<T, Stream<T>>

A lazy pipeline of elements: intermediate operations (map/filter/flatMap) describe, one terminal operation (collect/reduce/count…) executes. Single-use; never mutates its source.

Key methods

`Stream<R> map(Function<T,R>) / Stream<T> filter(Predicate<T>)`	The transform/select pair.
`Stream<R> flatMap(Function<T, Stream<R>>)`	1→many + flatten.
`Stream<T> sorted() / distinct() / limit(n) / skip(n)`	Stateful shapers.
`Stream<T> takeWhile / dropWhile(Predicate<T>)`	Cut ordered streams at a condition (Java 9).
`<R,A> R collect(Collector<T,A,R>)`	Mutable reduction — the main terminal.
`Optional<T> reduce(BinaryOperator<T>) / T reduce(T, BinaryOperator<T>)`	Fold with an associative op.
`boolean anyMatch/allMatch/noneMatch(Predicate<T>)`	Short-circuit predicates.
`Optional<T> findFirst() / findAny()`	Short-circuit retrieval.
`List<T> toList()`	Unmodifiable list (Java 16) — the everyday terminal.
`static <T> Stream<T> of(T...) / iterate(seed, f) / generate(s)`	Sources.