Which two methods from the java.util.stream.Stream interface perform a reduction operation? (Choose two.)

Question

Options

• Acount ()
• Bcollect ()
• Cdistinct ()
• Dpeek ()

• A
  76% (16)
• C
  14% (3)
• D
  10% (2)

Explanation

count() returns a single long value representing the total number of elements, making it a terminal reduction that collapses the entire stream into one result. collect() is a mutable reduction that accumulates stream elements into a container such as a List or Map - it also terminates the stream and produces a single aggregated result.

distinct() and peek() are both intermediate operations - they return a new Stream, meaning they transform the pipeline but never produce a final result on their own. distinct() filters duplicates, and peek() is a debugging hook that lets you inspect elements as they pass through without consuming them.

Memory tip: If a Stream method returns a Stream, it's intermediate - not a reduction. Reductions always terminate the pipeline and hand back a concrete value, collection, or OptionalX type.

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