Which statement about Java Streams is true?

Which statement about Java Streams is true?

• A. They are lazy and only evaluate when a terminal operation is invoked.
• B. They store all intermediate results in memory eagerly.
• C. They modify the underlying data source.
• D. They can only be used with lists.

Answer: (A)

Java Streams are lazy, meaning the pipeline of operations you set up (like map, filter, or limit) doesn’t do any work until a terminal operation runs (such as collect, forEach, or count). This laziness lets the runtime optimize and even short-circuit processing because elements flow through the pipeline only as needed to produce the final result. Because of this, intermediate steps aren’t eagerly computed or stored; work is performed as the terminal operation consumes the stream. Streams themselves don’t modify the underlying data source; they read from it and produce results, not change the source data. And they aren’t limited to lists—streams can come from arrays, sets, maps, other collections, or even generated data or I/O sources.

Java Streams are lazy, meaning the pipeline of operations you set up (like map, filter, or limit) doesn’t do any work until a terminal operation runs (such as collect, forEach, or count). This laziness lets the runtime optimize and even short-circuit processing because elements flow through the pipeline only as needed to produce the final result. Because of this, intermediate steps aren’t eagerly computed or stored; work is performed as the terminal operation consumes the stream. Streams themselves don’t modify the underlying data source; they read from it and produce results, not change the source data. And they aren’t limited to lists—streams can come from arrays, sets, maps, other collections, or even generated data or I/O sources.