Clarify "at line #" on exam

[Kevin O'Mara]

When the exam question says - what is true at line 14, does that mean before the code at line 14 is executed, or the code at line 14 has been executed?

[Byju Joy]

Right, there is ambiguity. Could you post that question?

[Ankit Garg]

Well it generally means that when the code at line 14 is getting executed . So basically you can say that before line 14 is executed. Actually it depends on the options. Lets take a dummy question

Double d = 10.0;
d = null;
double dd = d.doubleValue();

What is true at line 3
1. d is eligible for garbage collection - true
2. d is garbage collected - false as this is not guaranteed
3. an exception is thrown - true

[Kevin O'Mara]

I don't remember the exact code from the question - but it was something like:

class t1 {
	t1 t2;
}

public class LineExample {
	public static void main(String[] args) {
		LineExample le = new LineExample();
		t1 t21 = new t1();
		t1 t20 = le.getT1(t21);
	}

	t1 getT1(t1 t30) {
		t1 t10 = new t1(); t1 t11 = new t1(); t1 t12 = new t1();
		t1 t13 = new t1(); t1 t14 = new t1(); t1 t15 = new t1();
		t10.t2 = t15; t30.t2 = t12;
		t11 = t15; t13 = t12;
		return t10;
	}
}

In my example, the question would be phrased "how many objects are eligible for garbage collection at line 18? This is the closing brace of the method getT1(). I believe the answer is 2 if at line 18 means the JVM is about to execute line 18, but 3 if line 18 has been executed and the method has ended.

[Bert Bates]

The real exam probably does a better job than most mock exams in terms of avoiding such ambiguities. I think you'll see a couple of more or less standard approaches on the real exam:

15. m1.x = null;
16. // doStuff
17. }

When line 16 is reached...


or

16. // some code

After line 16 executes...

hth,

Bert

[Kevin O'Mara]

The example is from the real exam (more or less). The point I remember for sure is the at line # was the closing brace for the method - which is of course after the return statement. Obviously makes a big difference whether the method is totally over and the instance variables have been free'd - or if they are about to be free'd.

Is there anywhere one can go to get a definitive clarification?

[Bert Bates]

Hi Kevin,

No offense, but what you've described isn't on the SCJP 6 exam. So, there's some little detail that you've forgotten. I checked with Sun and, while there are questions similar to what you remember, in every case there is some important difference than what you've discussed.

hth,

Bert

[Kevin O'Mara]

Bert - I just took the SCJP 6 exam Monday. I don't remember the exact code snippet - and they have pretty strict rules about writing things down to take with you - LOL. I am certain that the question was "how many objects are eligible for garbage collection at line 14 (in the real test). And I am certain that line 14 was the closing brace for the method.

Maybe I overlooked some other trick that would have made the question of whether or not the method was over and "cleaned up" a moot point - e.g., line 14 was after the return. I answered "2" - using the analogy of a Debugger; if the Debugger was at line 14, it would be ready to "step into line 14" and end the method. Of course being the real exam, I also don't know if "2" was the correct answer.

Regardless, you mentioned that you checked with Sun - how did you do that? I've looked at the Prometric and Sun sites and don't see where I can pose such a question directly.

Thanks for your attention to this question. As you might guess, I did not pass - but was very close. When I retake the exam, I can't afford to miss any questions due to misunderstanding the question - not the concept.