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Mistake in GuideBook for SCJP Java 6.0, Chapter 10, Self Test question 11

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Given the following directory structure:

And given the contents of and

If the current directory is "test", and myApp/Foo.class is placed in a JAR file called MyJar.jar
located in test, which set(s) of commands will compile and produce the output 8?
(Choose all that apply.)

A is correct. Given the current directory and where the necessary files are located, these
are the correct command line statements.

B and D are wrong because javac MyJar.jar is incorrect syntax. C is wrong
because the -classpath in the java invocation does not include the test directory.
(Objective 7.5)

The A answer is not correct, because the Foo class cannot be found when executing the GetJar. None of the answers is correct.
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Hi Tomasz, welcome to javaranch.

This error has been noticed before and has been reported here. You can submit any other error that you find in the book in that topic created by Bert Bates...
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I'm having trouble with this one too.

The other thread linked above says "GetJar refers to "Foo.d" but does not either import myApp.* or refer to Foo.d by its fully qualified name. There is no way to get this code to compile." That is not the case in my book, or in the OP's (Original Poster). My book also has the following which uses the fully qualified name.

Furthermore, option "A" compiles the code fine on my machine, so long as the directory structure is preserved in the Jar file.

The jar can be created with after compiling the the java file using
javac -classpath MyJar.jar
jar -cf myJar.jar myApp/Foo.class

However my issue is that the explanation for option C seems incorrect.

1st) there is no "" in option C. It should be "MyJar.jar"
2nd) even if it was written correctly I would take this to mean

java -classpath test/Myjar.jar GetJar

which is not the reason it would not work.

3rd) I think what it is trying to say is that the Jar file (MyJar.jar) does not include the GetJar.class file (which is in the test directory).

A jar that contains this file can be created using the following command. This will allow option C to run and be correct as well. But it was not specifically said that these files were or were not in the Jar file.

jar -cf MyJar.jar GetJar.class myApp/Foo.class


jar -cf MyJar.jar *

So really C could also be correct, unless we assume that the only class in the Jar is myApp/Foo.class
perhaps giving the jar file creation command (and location executed) in place of the statement that "myApp/Foo.class is placed in a JAR file called MyJar.jar" would be much more clear.
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I think the correct answer should be:


when I compile and run the program as above it prints 8.
I've got no option but to sell you all for scientific experiments. Or a tiny ad:
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