Sybex Study Guide 1Z0-815 Page 486 Review Question #7

[Christian Schulz]

Hi,

I have a question about review question #7 on page 486 of the Study Guide for exam 1Z0-815.

The review question asks:

Suppose module puppy depends on module dog and module dog depends on module animal. Which two lines allow module puppy to access the animal.behavior package in module anima? (Choose two)

module animal {
  exports animal.behavior to dog;
}
module dog {
  ___ animal; // line S
}
module puppy {
  ___ dog; // line T
}

The correct answer according to page 526 are D (requires on line T) and G (requires transitive on line S).

As I see it, the package animal.behavior can never be accessed from within module puppy directly, because it is only exported explicitly to module dog.
I have the following code:

animal/
├── animal
│   └── behavior
│       └── Behavior.java
└── module-info.java

module animal {
	exports animal.behavior to dog;
}

// animal.behavior.Behavior.java
package animal.behavior;

public class Behavior {
	public void behave() {
		System.out.println("behave!");
	}
}

dog/
├── dog
└── module-info.java

module dog {
	requires transitive animal;
}

puppy/
├── module-info.java
└── puppy
    └── MyPuppy.java

module puppy {
	requires dog;
}

// puppy.MyPuppy.java
package puppy;
import animal.behavior.*;

public class MyPuppy {
	public static void main(String[] args) {
		var behavior = new Behavior();
		behavior.behave();
	}
}

When compiling the puppy module, I get the following error

$ javac -p mods/ -d puppy/ puppy/puppy/MyPuppy.java puppy/module-info.java 
puppy/puppy/MyPuppy.java:2: error: package animal.behavior is not visible
import animal.behavior.*;
             ^
  (package animal.behavior is declared in module animal, which does not export it to module puppy)
1 error

When I change the module-info.java from module animal so that it only reads "exports animal.behavior" (without the "to dog" at the end). The code runs successfully and prints "behave!".
Am I missing something?

[Jeanne Boyarsky]

Christian,
You are correct. This is an error. Adding to the errata now. (It shouldn't say "to dog")

[Christian Schulz]

Jeanne,

thanks for your reply. Glad I understood it correctly.

[Gerson Freitas]

Shouldn't

requires transitive dog;

be considered?

Putting transitive or not, the requires does import the dog module.

Making "G and H" a valid option either.  

[Jesse Silverman]

Gerson Freitas wrote:Shouldn't

requires transitive dog;

be considered?

Putting transitive or not, the requires does import the dog module.

Making "G and H" a valid option either.  

I agree.  If Gerson and myself are not confused, this was an example of a question that posed three correct answers and told us to choose two.

While the requires transitive says more than what is needed, it would as far as I can see compile fine and work fine for this purpose.

Whether it would be necessary for the overall situation or not would only be known by seeing more information than given in the problem, but it would certainly be sufficient to allow puppy to access animal.behavior.

The tests are already so full of tricks, this is rough.  Either three answers should be accepted (and in fact required) or one of either the requires transitive dog or requires dog choices should be removed.

[Jeanne Boyarsky]

This particular question says "choose two." We all agree on one of them> That leaves you deciding between which of the requires is the best choice. I would argue that the more specific one is better.

Jesse: Where's your lawyer hat?