Is volatile is only for instance variable? (error on ExamLab test 3)

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posted 13 years ago

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Hi,
on examlab test 3, reviewing my answers, I've read that volatile is a keyword applicable only to instance variables.

In fact, this is false, because if you try to compile a program with a static volatile variable, the program perfectly compile, and also in the javadoc there are sun examples of static volatile variables:

http://java.sun.com/docs/books/jls/second_edition/html/classes.doc.html

Can someone confirm this to me ?

Thanks.

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Jan Cumps

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posted 13 years ago

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I have moved this post to our Mock Exam Errata forum.
That forum is dedicated to "problems with mock exams everywhere".

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Jim Hoglund

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posted 13 years ago

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Good point. The question should have been about member variables,
as compared to stack or local variables. And it's not just primitives.
Remember that a reference variable can be volatile too.

Jim ... ...

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Devaka Cooray

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posted 13 years ago

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Emanuele,

Thanks for the feedback, and sorry, I didn't see this post before
Can you please tell me the question number where you found this problem - if so, I can make it correct with the next release of ExamLab. For me, I couldn't find a statement like that in practice exam 3.

Thanks,

Devaka

Author of ExamLab - a free SCJP / OCPJP exam simulator
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M. White

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posted 13 years ago

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same goes with volatile modifier, it compiles on a static member. As stated is K&B Study Guide 6 Page 72:

The transient modifier applies only to instance variables.
The volatile modifier applies only to instance variables.

As stated also in the url you given by Emanuele:

FieldModifiers:
FieldModifier
FieldModifiers FieldModifier

FieldModifier: one of
public protected private
static final transient volatile

Im not sure if this should be on a separate thread .

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