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Access to private members
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vijayk kumar
Greenhorn
Joined: Jul 29, 2006
Posts: 18
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Can the object refernce be used to access a private member?
If so in what situations?
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Ernest Friedman-Hill
author and iconoclast
Marshal
Joined: Jul 08, 2003
Posts: 24081
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Only from code in the same class; any instance of class X can access the private members of any other instance of class X, but no code in any other classes can.
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[Jess in Action][AskingGoodQuestions]
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vijayk kumar
Greenhorn
Joined: Jul 29, 2006
Posts: 18
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Yes , I get it .Now I will try with an example.
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Pratibha Malhotra
Ranch Hand
Joined: Dec 21, 2003
Posts: 199
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But is not illegal to happen.  I mean private variables should only available for owner only.
Is it a bug or an expected behaviour. 
[ July 31, 2006: Message edited by: Rewa Dev ]
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~ Pratibha Malhotra<br /> <br />Sun Certified Java Programmer<br />SCEA 1.4 (In Progress)<br />~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />"Many of life's failures are people who did not realize how close they were to success when they gave up!!"
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Ilja Preuss
author
Sheriff
Joined: Jul 11, 2001
Posts: 14112
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It's expected behaviour.
The reason to make fields private is so that code outside the class doesn't get coupled to implementation details.
With other words, the purpose of access modifiers is mainly to manage the static structure of the source code, not to manage runtime dependencies of objects.
Does that sound reasonable?
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The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus
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Ernest Friedman-Hill
author and iconoclast
Marshal
Joined: Jul 08, 2003
Posts: 24081
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Originally posted by Rewa Dev: Is it a bug or an expected behaviour.
It is definitely expected behavior. Some languages (Java, C++, and others) have class-based encapsulation, in which the class is the level of protection. Others (Ruby is a good example) have object-based encapsulation, in which one object can't call the private members of another; this is rather rarer. Both have their advantages; note that writing comparison methods, clone methods, etc, can be difficult in object-based encapsulation systems.
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subject: Access to private members
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