Java OCA OCP Practice Question 2771

Question

Which of the following is true? 

List<Integer> l1 = Arrays.asList(1, 2, 3); 
List<Integer> l2 = Arrays.asList(4, 5, 6); 
List<Integer> l3 = Arrays.asList(); 
Stream.of(l1, l2, l3).map(x -> x + 1) 
  .flatMap(x -> x.stream()).forEach(System.out::print);
  • A. The code compiles and prints 123456.
  • B. The code compiles and prints 234567.
  • C. The code compiles but does not print anything.
  • D. The code compiles but prints stream references.
  • E. The code runs infinitely.
  • F. The code does not compile.
  • G. The code throws an exception


F.

Note

If the map() and flatMap() calls were reversed, choice B would be correct.

In this case, the Stream created from the source is of type Stream<List<Integer>>.

The Function in map expects an Integer rather than a List<Integer>, so the code does not compile.




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