• Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other all forums
this forum made possible by our volunteer staff, including ...
  • Campbell Ritchie
  • Paul Clapham
  • Ron McLeod
  • Bear Bibeault
  • Liutauras Vilda
  • Jeanne Boyarsky
  • Tim Cooke
  • Junilu Lacar
Saloon Keepers:
  • Tim Moores
  • Tim Holloway
  • Stephan van Hulst
  • Jj Roberts
  • Carey Brown
  • salvin francis
  • Frits Walraven
  • Piet Souris

OCP Oracle Certified Professional Java SE8 Programmer II Study Guide - Error on test question 22

Ranch Hand
Posts: 32
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
The question is:
What is the result of executing the following program?

Answer options:

A. It prints 0 1 2 3 4
B. It prints 1 2 3 4 5
C. It prints null null null null null
D. It hangs indefinitely at runtime.
E. The output cannot be determined.
F. The code will not compile because of line n1.
G. The code will not compile because of line n2.

The correct answer is:

F. The key to solving this question is to remember that the execute() method returns
void, not a Future object. Therefore, line n1 does not compile and F is the correct answer.
If the submit() method had been used instead of execute(), then C would have been the
correct answer, as the output of submit(Runnable) task is a Future<?> object which can
only return null on its get() method.

I'm absolutely agreed with the answer as I answer it the same. What is confuses me is a propagated alternative: in case of using of submit() method, passed lambda expression  () -> counter++ would be evaluated as pure Callable not Runnable (in fact this lambda can also be evaluated as Runnable due to compiler contract, the same as Function lambda can be evaluated as Consumer if required) and program will end up with the answer A.
Posts: 4234
jQuery Eclipse IDE Java
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Ah, yes, the answer is correct, but the alternate text is wrong.  I believe in the original version, the lambda was actually:

Somewhere along the way, the {} was dropped, making the alternate answer incorrect.  Thanks for finding this, we will update the text!
It's just a flesh wound! Or a tiny ad:
Building a Better World in your Backyard by Paul Wheaton and Shawn Klassen-Koop
    Bookmark Topic Watch Topic
  • New Topic