Some minor typos in chapter 5 (Java OCA 8 Programmer I Study Guide, Sybex)

[Mushfiq Mammadov]

1. On page 244, "Calling Inherited Class Members" section, the second paragraph:

To reference a member in a parent class, you can just call it directly, as in the following example with the output function displaySharkDetails():

Maybe function should be method.


2. On page 254, "Overriding vs. Hiding Methods" section, the second paragraph, the second sentence:
Maybe ParentClassName.method() should be new ParentClassName().method() . Because we call static methods with this syntax - ParentClassName.method(). But in this case we refer overriden method.


3. On page 272, second code example, Bear class:

    public class Bear implements Herbivore, Omnivore {  // line 1
       public int eatPlants() {      // DOES NOT COMPILE
           System.out.println("Eating plants: 10");
           return 10;
       }
       public void eatPlants() {     // DOES NOT COMPILE
          System.out.println("Eating plants");
       }
    }

line 1 does not compile too. It may be added comment to this line.


4. On page 276, the last paragraph:

For example, the following class overrides one default interface method and redeclares a second interface method as abstract:

class should be interface, because there are no class in the following example, both of them are interface.


5. On page 286, the code output:
"Feeding: " should be "Feeding reptile "


6. On page 347, the first sentence of mock explanation #8:
We know that interface variables are public, static and final. In the explanation public and static are noted but final isn't.


7. On page 349, the second sentence of mock explanation #18:
"..since int is not a subclass of String." should be "..since String is not a subclass of int."


Online materials

8. Chapter Tests --> Chapter 5 --> the explanation of test 5:
"Option C" should be "Option A"



9. Chapter Tests --> Chapter 5 --> the explanation of test 10:
extend should be extends.

[Roel De Nijs]

Mushfiq Mammadov wrote:1. On page 244, "Calling Inherited Class Members" section, the second paragraph:

To reference a member in a parent class, you can just call it directly, as in the following example with the output function displaySharkDetails():

Maybe function should be method.

Yep, that's probably a better choice of words.

Mushfiq Mammadov wrote:2. On page 254, "Overriding vs. Hiding Methods" section, the second paragraph, the second sentence:
Maybe ParentClassName.method() should be new ParentClassName().method() . Because we call static methods with this syntax - ParentClassName.method(). But in this case we refer overriden method.

Definitely agree! ParentClassName.method() is the syntax to invoke a static method. But from the context of that paragraph new ParentClassName().method() is also not correct (because you are creating a new instance of the parent class, instead of using the method of the current object). You must use super.method() to explicitly invoke (and execute) a parent method when it's overridden. As illustrated in this code snippet

class AlternateFuel {
    int getRating() { return 42; }
    void go() { System.out.println("go:" + getRating()); }
}
class BioDiesel extends AlternateFuel {
    int getRating() { return 65; }
    void go2() { System.out.println("go2:" + super.getRating()); }
    public static void main(String[] args) {
        new BioDiesel().go();
        new BioDiesel().go2();
    }
}

Output:
go:65
go2:42

Mushfiq Mammadov wrote:3. On page 272, second code example, Bear class:
...
line 1 does not compile too. It may be added comment to this line.

True! (By the way, that's a difference with Java 7, because if you compile the Bear class you only have two compiler errors)

Mushfiq Mammadov wrote:4. On page 276, the last paragraph:

For example, the following class overrides one default interface method and redeclares a second interface method as abstract:

class should be interface, because there are no class in the following example, both of them are interface.

You are spot-on!

Mushfiq Mammadov wrote:5. On page 286, the code output:
"Feeding: " should be "Feeding reptile "

Correct! Or the feed() method of the ZooWorker class can be changed as well to match with the output

Mushfiq Mammadov wrote:6. On page 347, the first sentence of mock explanation #8:
We know that interface variables are public, static and final. In the explanation public and static are noted but final isn't.

True! final is missing and should be added to the list.

Mushfiq Mammadov wrote:7. On page 349, the second sentence of mock explanation #18:
"..since int is not a subclass of String." should be "..since String is not a subclass of int."

Correct again! The method defined in the interface has int as return type.

Mushfiq Mammadov wrote:8. Chapter Tests --> Chapter 5 --> the explanation of test 5:
"Option C" should be "Option A"

Indeed!

Mushfiq Mammadov wrote:9. Chapter Tests --> Chapter 5 --> the explanation of test 10:
extend should be extends.

If C is intended to be a correct answer, the answer option must be changed as well (and not only the text in the explanation). Because currently option C is an incorrect answer (as the keyword is extends and not extend)

Hope it helps!
Kind regards,
Roel

[Jeanne Boyarsky]

1) While method would be better, function and method tend to get used interchangeably so don't worry about it.

2,3, 4) Agreed. Logged as errata.

5) Roel's fix is what we intended.

6, 7) Agreed. Logged as errata

8, 9) Agreed. Interestingly both are right in the printed book. Which means that error doesn't belong to Scott or myself.

[Jeanne Boyarsky]

Roel De Nijs wrote:If C is intended to be a correct answer, the answer option must be changed as well (and not only the text in the explanation). Because currently option C is an incorrect answer (as the keyword is extends and not extend)

Agreed. And that's more significant than the reported problem!

[Mushfiq Mammadov]

Roel De Nijs wrote: Definitely agree! ParentClassName.method() is the syntax to invoke a static method. But from the context of that paragraph new ParentClassName().method() is also not correct (because you are creating a new instance of the parent class, instead of using the method of the current object). You must use super.method() to explicitly invoke (and execute) a parent method when it's overridden.

You are right, Roel, I forgot super keyword

Roel De Nijs wrote: If C is intended to be a correct answer, the answer option must be changed as well (and not only the text in the explanation). Because currently option C is an incorrect answer (as the keyword is extends and not extend)

I didn't write it, because I reported it in this thread

[Roel De Nijs]

Mushfiq Mammadov wrote:

Roel De Nijs wrote: If C is intended to be a correct answer, the answer option must be changed as well (and not only the text in the explanation). Because currently option C is an incorrect answer (as the keyword is extends and not extend)

I didn't write it, because I reported it in this thread

But that's the book and this is online It's strange to see that the explanation in the printed book is correct (using extends), but in the explanation online it's not. Or maybe the online publisher noticed the "C is correct" part and noticed extend in option C, and helped the authors by fixing that "typo" and replaced extends with extend

[Mushfiq Mammadov]

In this thread I noted that the same typos which were reported for paper book existed for online materials. Therefore I didn't note that online typos which were already reported for paper book.
Sometimes I notice that there is a bit difference between online materials and paper book. I think such maybe the paper book were read again once and were edited before printing

[Roel De Nijs]

Mushfiq Mammadov wrote:In this thread I noted that the same typos which were reported for paper book existed for online materials. Therefore I didn't note that online typos which were already reported for paper book.

Yeah, now I remember it again you should have added that thread to your previous post as well. You should never rely on my drastically fading memory

[Mushfiq Mammadov]

Roel De Nijs wrote:Yeah, now I remember it again You should have added that thread to your previous post as well. You should never rely on my drastically fading memory

Don't worry for your memory because you were on holiday when I wrote that post Maybe you read all new posts very quickly after holiday so you don't remember it instantly

[Jeanne Boyarsky]

Mushfiq Mammadov wrote:Sometimes I notice that there is a bit difference between online materials and paper book. I think such maybe the paper book were read again once and were edited before printing

Maybe, but no. I actually checked our original manuscripts and they didn't contain that error. Which means it was only introduced in the online version. I'm guessing someone was trying to be helpful.