About Question enthuware.ocpjp.v8.2.1711 :

[admin]

Can you show a situation where the output contradicts the statement of option 3?

[Touciuciu]

The answer should be "It may print any combination of the keys". Tested with STS and the output was "a,b,c". It is true that most of the time it will print c and maybe it will combine it with a or b but the question says that we should be able to determine the possible output so one possible output is a, b, c. Very rare but possible, this is why your answer is wrong. Please admit that is wrong and correct it.

[admin]

Yes, it can print "a, b, c". That is why option 3 is correct. Please read the option carefully. It says "except".
Option 1 cannot be correct because it will never print these four possibilities:
1. a,
2. b,
3. a, b,
4. b, a

[floryan]

I think the answer should be, "It may print any combination of the keys." In a real world scenario the selected answer sounds most reasonable. But thread execution in this case is unpredictable and in the rarest chance it is possible that the second thread runs first, prints everything and then the first thread runs. Thus the answer must be unpredictable.

Yes, this should be the correct answer. Especially because there's is such a huge focus on the unpredictability of thread execution in this exam.

[admin]

I think the answer should be, "It may print any combination of the keys." In a real world scenario the selected answer sounds most reasonable. But thread execution in this case is unpredictable and in the rarest chance it is possible that the second thread runs first, prints everything and then the first thread runs. Thus the answer must be unpredictable.

Yes, this should be the correct answer. Especially because there's is such a huge focus on the unpredictability of thread execution in this exam.

No, it should not be correct. As replied above, can you show a situation where the output contradicts the statement of option 3?

[floryan]

Ah okay, gotcha. Misleading but technically correct I guess. I didn't see the second page of the conversation here, sorry.

[Mark7777]

So is the answer, "any combination as long as it contains a "c"? Something like that?

[admin]

Yes, you could say that.

[Touciuciu]

Yes, the question is very confussing because you might think that:
-> Any combination of the keys can be printed (one of any combination is a, b, c which is possible)
-> Any combination, excluding .... (one of any combination is a, c or b, c)
-> The output cannot be determined

We understand the explanation but the question statement and answers are confussing and missleading. You can have a multiple choice option for this question

[Bhaskar]

The correct option does mention it. It says, "It may print any combination except: a, or b, or a, b, or b, a". This includes c a b and c b a.

HTH,
Paul.

'b, a' is a possible output because ConcurrentHashMap guarantees no order of elements right? i.e, [b,a,c] or [b,c,a] is a possible key entry in the Map.

[admin]

Correct.

[jost.boekemeier]

Yes, it can print "a, b, c". That is why option 3 is correct.

Well, if it can print a,b,c, then option 3 is certainly not correct, as its exclude list cannot be empty: "except: a, or b, or a, b, or b, a".

You could add "none" to the exclude list to fix this, but as it stands, option #1 is more correct than option #3.

[admin]

Yes, ideally, "none" could also be added to the exclude list.