Which statement is true about java.util.Stream?

Question

Options

• AA stream cannot be consumed more than once.
• BThe execution mode of streams can be changed during processing.
• CStreams are intended to modify the source data.
• DA parallel stream is always faster than an equivalent sequential stream.

• A
  76% (45)
• B
  3% (2)
• C
  5% (3)
• D
  15% (9)

Explanation

Once a Stream is consumed by a terminal operation (like collect(), forEach(), or count()), it is closed and cannot be reused - attempting to do so throws an IllegalStateException, making A correct. B is false because a stream's execution mode (sequential vs. parallel) is set at creation or via parallel()/sequential() calls, but once a terminal operation begins, the mode is fixed - you can't switch mid-processing. C is false because streams are designed for read-only functional-style processing; modifying the source during stream traversal leads to undefined behavior and is explicitly discouraged. D is false because parallel streams introduce thread-coordination overhead, so for small datasets or simple operations, sequential streams are often faster - parallelism helps only when the workload is large enough to offset that cost.

Memory tip: Think of a stream like a garden hose - once the water (data) flows through and the tap (terminal operation) is turned off, you need a new hose for the next run. "One flow, one go."

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