Stream API Flashcards
7 cards from real 1Z0-819 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Stream API flashcards as text
Which terminal operation on a Stream returns an OptionalInt containing the minimum value?
Answer: IntStream.min()
IntStream.min() returns an OptionalInt with the minimum value of the stream.
What does the following produce? Stream.of(1,2,3).map(n -> n * 2).filter(n -> n > 3).count()
Answer: 2
After doubling: 2,4,6; filtering >3 yields 4,6; count() returns 2.
Which Collector groups elements into a Map where keys are Boolean values?
Answer: Collectors.partitioningBy()
Collectors.partitioningBy() splits elements into true/false groups based on a Predicate.
What is the result of IntStream.range(0, 5).sum()?
Answer: 10
IntStream.range(0,5) produces 0,1,2,3,4; their sum is 10.
Which method converts a Stream> to a Stream containing only present values in Java 9+?
Answer: stream.flatMap(Optional::stream)
Optional.stream() was added in Java 9, making flatMap(Optional::stream) the idiomatic approach.
What does Collectors.joining(", ", "[", "]") produce for Stream.of("a","b","c")?
Answer: [a, b, c]
joining with delimiter ", ", prefix "[", and suffix "]" produces [a, b, c].
Which statement about Stream.iterate() in Java 9 is correct?
Answer: It can accept a Predicate as a stop condition
Java 9 added a three-argument Stream.iterate(seed, predicate, unaryOperator) that stops when the predicate is false.