Questions/errata for Sybex OCP 17 Study Guide

[Guillaume Bailly]

Hi,

For online question tb864585.JaSE17SG.c09.15, I would suggest removing <Integer> on the left side and moving the type on the right side of the assignment.
This makes it clearer in my opinion that the blank refers to both the main type and the generics part.

Guillaume

[Guillaume Bailly]

Hi,

Question tb864585.JaSE17SG.c04.19 in the online test bank makes use of a static method in Arrrays (with three "r")
This is a minor concern, but I still wanted to add it for completeness.

Guillaume

[Val Martinez]

Thank you so much.
I also get confused, because I think option b is a correct overloading, but not overriding.

By the way, Jeanne; where did you wrote that long explanation?. I'd be interested on read it. Thanks

Jeanne Boyarsky wrote:

Guillaume Bailly wrote:Hi,

Spoiler alert, this is a question about the review questions at the end of chapter 9.

I don't really get why option B in question 7 is seen as valid (pages 524 and 940).
After all, if I were to declare Alpaca as an interface, this wouldn't be true.

Can someone enlighten me?

I wrote a whole long explanation of why and then got to the end and realized it was wrong. Logged as an errata.

The quick test is to use an @Override tag and see if it is allowed. It is not.

[Campbell Ritchie]

VM: Welcome to the Ranch

[Val Martinez]

Campbell Ritchie wrote:VM: Welcome to the Ranch

Thanks Ritchie

Another question.
I become a bit confused while studying chapter 10.

In the table 10.10, (page 571) where most of Collectors methods are shown, the groupingBy says it reutns a Map<k, List<T>>.  And that is not totally true. For example,  you can program this

LongStream.of(6, 8, 10).mapToInt(x-> (int)x).boxed().collect(Collectors.groupingBy(x ->x, Collectors.toSet())).entrySet().iterator();

and each value of the map collected will be a Set (and not a List).
So, I would appreciate to use other Generic Type or info to describe more exactly the returned type of each groupingBy version.

Thank you.

[Stephan van Hulst]

One of the overloads of groupingBy() DOES return a Map<K, List<T>>. That there exist other overloads that return something different doesn't make the former fact any less true.

If that is the only overload that is listed in the table, then I agree that it seems arbitrary to only list that return value, and not others as well.

[Val Martinez]

Stephan van Hulst wrote:... If that is the only overload that is listed in the table..

Exactly!, that's the thing.

Cheking the official API helped me to understand there were others versions/overloads that return different types (ie,  groupingBy )

[Mike Simmons]

None of the overloads returns Map<K,List<T>>.

One does return a  Collector<T,?,Map<K,List<T>>>

[Stephan van Hulst]

Yes, sorry, that's what I meant.

[Hector Beaujean]

Hi all.

I'm studiing for exam number 1Z0-829, using Sybex OCP 17 Study Guide.
I've already read the errata list of the book, but I still have concerns.

For example : Chapter 1, review questions page 55, question 5.
If an object is eligible for GC after line 13 (answer A), why saying it is also eligible for GC after line 14 is wrong (answer B) ?
Would the real exam say "...object become eligible for the first time after line..." ?

Regarding question 9, default value for primitive numerics is 0 (mathematical 0).
Will the exam ask to reply "0", "0.0", "0f", "0F" or "\u000", not simply "0" ? 0 will be wrong for everything but "int" ?

I Know I have to go back in my student shoes, proud of my sun developer certication (yes : sun !) !

Anyway, does any reader here find these questions interesting ?

Regards,
Hector

PS for Moderators.
As I'm new here, I hope I'm in the right place.
Feel free to confirme that to me, or to educate me !

[Guillaume Bailly]

Hector Beaujean wrote:For example : Chapter 1, review questions page 55, question 5.
If an object is eligible for GC after line 13 (answer A), why saying it is also eligible for GC after line 14 is wrong (answer B) ?
Would the real exam say "...object become eligible for the first time after line..." ?

I might have posted an answer for this question somewhere. Anyway, in such a case, you should assume the most restrictive. This is also the best way you (or the exam creators) can test your knowledge.

[Guillaume Bailly]

Hector Beaujean wrote:Regarding question 9, default value for primitive numerics is 0 (mathematical 0).
Will the exam ask to reply "0", "0.0", "0f", "0F" or "\u000", not simply "0" ? 0 will be wrong for everything but "int" ?

I passed the test recently, the exam creators are not that mean, no. There is also no real difference in the code, unless you format and print the value somewhere.

[Hector Beaujean]

Guillaume Bailly wrote:

Hector Beaujean wrote:For example : Chapter 1, review questions page 55, question 5.
If an object is eligible for GC after line 13 (answer A), why saying it is also eligible for GC after line 14 is wrong (answer B) ?
Would the real exam say "...object become eligible for the first time after line..." ?

I might have posted an answer for this question somewhere. Anyway, in such a case, you should assume the most restrictive. This is also the best way you (or the exam creators) can test your knowledge.

Thanks for your reply.
I'm note sure of what you mean by

Guillaume Bailly wrote:the most restrictive

(excuse my english).

The question say "is eligible after line..." not "become eligible after line...".
In the real exam, I have to say "no, the object is not eligible for CG at this point" even if it is ?
If so, it's awkward for me...

[Guillaume Bailly]

Hector Beaujean wrote:The question say "is eligible after line..." not "become eligible after line...".
In the real exam, I have to say "no, the object is not eligible for CG at this point" even if it is ?
If so, it's awkward for me...

No no, you're right, and in that sense you could consider both options to be correct.
If it's eligible for GC somewhere in the code, it will always be so later on in the same code.
Hope it's clear now, otherwise let me know.

You can find my original answer here: https://coderanch.com/t/752987/certification/Errata-OCP-Developer-Study-Guide

[Hector Beaujean]

Guillaume Bailly wrote:

Hector Beaujean wrote:Regarding question 9, default value for primitive numerics is 0 (mathematical 0).
Will the exam ask to reply "0", "0.0", "0f", "0F" or "\u000", not simply "0" ? 0 will be wrong for everything but "int" ?

I passed the test recently, the exam creators are not that mean, no. There is also no real difference in the code, unless you format and print the value somewhere.

In the book p9, the review question 6 says :
"A. An instance variable of type float defaults to 0.".
The answer to the review questions p911 says :
"A. is incorrect because float should have a decimal point.".

But :

float f = 0.0; //Don't even compile

, delault value is mathematical 0 (litetal to say that for float is 0f or 0F) and

float f = 0f; //Compile

I think quesion and/or answer have to be rephrase.

Do you agree ?
Should I propose an erratum ?

[Guillaume Bailly]

Hector Beaujean wrote:In the book p9, the review question 6 says :
"A. An instance variable of type float defaults to 0.".
The answer to the review questions p911 says :
"A. is incorrect because float should have a decimal point.".

But :

float f = 0.0; //Don't even compile

, delault value is mathematical 0 (litetal to say that for float is 0f or 0F) and

float f = 0f; //Compile

I think quesion and/or answer have to be rephrase.

Do you agree ?
Should I propose an erratum ?

Well, when you look at option C, it's rather clear what is expected from the question. In this sense, option A remains a wrong option.
But I agree that the answer might have been a little bit more precise, it's true. A float defaults to 0.0f. Just saying a decimal point is required might not be precise enough.
Now, the fact that 0f compiles is because 0 is an int and an int can implicitly be cast to a float. This has nothing to do with default values.

[Caleb Josue Ruiz Torres]

Hello there,

There is a missing colon in Figure 3.3 (Chapter 3, Applying switch Statements - section). Here's an image depicting this report.


If the image isn't viewing inline over this post, you can actually see it at: (https://drive.google.com/file/d/1N0GjrnKdFyqDCK5sqIKkvI4HLX9vuO7s/view)



--
Caleb Josue Ruiz Torres
(https://www.calebjosue.com)

[Caleb Josue Ruiz Torres]

Chapter 3 - The Switch Expression (Section).

Figure 3.4 (The structure of a switch expression). Is missing a required semicolon at the end of the Switch Expression.


Image:


Again, if the image isn't displaying inline (I am starting to think this has to do with the internal image viewer on Google Drive instead of being a link directly to an image).

Here's the image URL: https://drive.google.com/file/d/1CZjJ7CjAZTBNbK4pn0y_C2erqo3BHEMV/view

Thanks.

[Emil Posmyk]

Hello all,

on the page lvii in assesment test, in the question 30 is:
catch (Exception e || RuntimeException e)
and you mention: 'Finally, line 10 does not compile as RuntimeException is a subclass of Exception in the multi-catch block, making it redundant'
which is totally fine, but it seems that even that, the double argument inside ('e') is incorrect  - can be only one and logical OR || shouldn't be there.

--
Emil

[Campbell Ritchie]

Emil Posmyk wrote:. . . the double argument inside ('e') is incorrect  - can be only one and logical OR || shouldn't be there.
Emil

I think that is correct

And . . . . . welcome to the Ranch

[Jeanne Boyarsky]

Guillaume Bailly wrote:Hi,

For online flashcard "fc864585.JaSE17SG.1.025" with following content:

"Besides itself, which primitive types can be implicitly cast to double?"

I would add char to the answer (not a "natural" numeric type, but still holds true for completeness).

Guillaume

I would not. It's not a numeric type and too obscure for the exam.

Cristian Uceda Garrido wrote:Hi,

Chapter 6, Q.34:

I understand that there are no true good choices here as all of them are useless. It gets down to pick the least worse 2 options among them.

Valid solutions are B and E. I agree with E but not with B. I think they should be D and E.

I disagree D has a side effect. But as you noted, no good choices.

Guillaume Bailly wrote:Hi,

On page 624, the first paragraph in "Formatting Numbers" mentions a NumberFormat interface.
Actually, NumberFormat is an abstract class.

Guillaume

So it is. Adding to errata

[Jeanne Boyarsky]

Guillaume Bailly wrote:Hi,

Regarding online question tb864585.JaSE17SG.c04.14, the answer mentions new Instant() as a valid option.
There is no public no-arg constructor for Instant actually, so this answer should be removed.

Guillaume

The book doesn't have B as correct. Will let the publisher know for the website

[Jeanne Boyarsky]

Guillaume Bailly wrote:Hi,

Question tb864585.JaSE17SG.c04.19 in the online test bank makes use of a static method in Arrrays (with three "r")
This is a minor concern, but I still wanted to add it for completeness.

Guillaume

Arrrg. Also right in the printed book. I'll let the publisher know about the website. I'm wondering now if they uploaded an early draft of the book to the web!

[Jeanne Boyarsky]

Val Martinez wrote:Thank you so much.
I also get confused, because I think option b is a correct overloading, but not overriding.

By the way, Jeanne; where did you wrote that long explanation?. I'd be interested on read it. Thanks

In a textbox on this forum. I didn't save/submit it because I realized while typing that my attempt at an explanation was wrong!

[Jeanne Boyarsky]

Val Martinez wrote:

Stephan van Hulst wrote:... If that is the only overload that is listed in the table..

Exactly!, that's the thing.

Cheking the official API helped me to understand there were others versions/overloads that return different types (ie,  groupingBy )

Noted and will figure out what to do next edition

[Jeanne Boyarsky]

Caleb Josue Ruiz Torres wrote:Hello there,

There is a missing colon in Figure 3.3 (Chapter 3, Applying switch Statements - section). Here's an image depicting this report.

Ooh. Good catch. Added to errata and credited you.

[Jeanne Boyarsky]

Caleb Josue Ruiz Torres wrote:Chapter 3 - The Switch Expression (Section).

Figure 3.4 (The structure of a switch expression). Is missing a required semicolon at the end of the Switch Expression.


Image:


Again, if the image isn't displaying inline (I am starting to think this has to do with the internal image viewer on Google Drive instead of being a link directly to an image).

Here's the image URL: https://drive.google.com/file/d/1CZjJ7CjAZTBNbK4pn0y_C2erqo3BHEMV/view

Thanks.

Agreed and added to errata. Thanks for the annotated screenshots. Makes it super easy to see what's wrong in the diagram.

[Jeanne Boyarsky]

Emil Posmyk wrote:Hello all,

on the page lvii in assesment test, in the question 30 is:
catch (Exception e || RuntimeException e)
and you mention: 'Finally, line 10 does not compile as RuntimeException is a subclass of Exception in the multi-catch block, making it redundant'
which is totally fine, but it seems that even that, the double argument inside ('e') is incorrect  - can be only one and logical OR || shouldn't be there.

--
Emil

This is true. It's already in the errata though.

I think I replied to everything in this thread now.

[Chris Fo]

Jeanne Boyarsky wrote:

Guillaume Bailly wrote:Hi,

On page 624, the first paragraph in "Formatting Numbers" mentions a NumberFormat interface.
Actually, NumberFormat is an abstract class.

Guillaume

So it is. Adding to errata

Errataception here :-) - on the errata website it says page 525 for this above, which isn't even in chapter 11.

[Campbell Ritchie]

Wrong page number? Good grief!
And welcome to the Ranch

[Emil Posmyk]

Jeanne Boyarsky wrote:

Emil Posmyk wrote:Hello all,

on the page lvii in assesment test, in the question 30 is:
catch (Exception e || RuntimeException e)
and you mention: 'Finally, line 10 does not compile as RuntimeException is a subclass of Exception in the multi-catch block, making it redundant'
which is totally fine, but it seems that even that, the double argument inside ('e') is incorrect  - can be only one and logical OR || shouldn't be there.

--
Emil

This is true. It's already in the errata though.

I think I replied to everything in this thread now.

I don't see it there. I was checking only here (I thought all correctly reported issues were there :-)):
https://www.selikoff.net/ocp17/

Thanks
Emil

[Saranya Eswaralal]

Hi,

Regarding online question tb864585.JaSE17SG.c02.09, the answer mentioned is the code compiles successfully and provides output.
But, When I tried executing in IDE, it provides java: illegal character: '\u02c3', please me to understand, which is correct option.

[Campbell Ritchie]

Welcome to the Ranch

Please show us who don't have that book/site the whole question.

[Chris Fo]

Chris Fo wrote:

Jeanne Boyarsky wrote:

Guillaume Bailly wrote:Hi,

On page 624, the first paragraph in "Formatting Numbers" mentions a NumberFormat interface.
Actually, NumberFormat is an abstract class.

Guillaume

So it is. Adding to errata

Errataception here :-) - on the errata website it says page 525 for this above, which isn't even in chapter 11.

Isn't this the place to give the feedback? Since it's not a new discovery but what was linked from errata page I didn't create a new thread but maybe I need for it to be seen?

[Jeanne Boyarsky]

Guillaume Bailly wrote:For online question tb864585.JaSE17SG.c09.15, I would suggest removing <Integer> on the left side and moving the type on the right side of the assignment.
This makes it clearer in my opinion that the blank refers to both the main type and the generics part.

That would change what are testing here. var cares greatly what is on the right side.

Guillaume Bailly wrote:Question tb864585.JaSE17SG.c04.19 in the online test bank makes use of a static method in Arrrays (with three "r")
This is a minor concern, but I still wanted to add it for completeness.

rrr. It's right in the printed book. Weird. Reported as an online only errata

[Jeanne Boyarsky]

Chris Fo wrote:Errataception here :-) - on the errata website it says page 525 for this above, which isn't even in chapter 11.

Fixed

Chris Fo wrote:Isn't this the place to give the feedback? Since it's not a new discovery but what was linked from errata page I didn't create a new thread but maybe I need for it to be seen?

I read new threads and replies at the same time. I've just been busy

[Jeanne Boyarsky]

Saranya Eswaralal wrote:Hi,

Regarding online question tb864585.JaSE17SG.c02.09, the answer mentioned is the code compiles successfully and provides output.
But, When I tried executing in IDE, it provides java: illegal character: '\u02c3', please me to understand, which is correct option.

You probably copy/pasted which gave you a mdash (smart dash) or the like. THere's no funky characters in the code.

[Carlo Maffi]

Hello,

on Chapter 11, page 639, paragraph "Specifying a Locale Category",
The paragraph ends with this sentence:
"You should also know that calling Locale.setDefault(us) after the previous code snippet will change both locale..."

However, "us" in Locale.setDefault(us) is not defined in the previous code snippet.
I believe this should change to
Locale.setDefault(new Locale("en", "US"))

Thank you

[Campbell Ritchie]

Welcome to the Ranch

I think the authors wanted you to impute a us variable of type Locale.