Immutable class in java

Question

I made my class immutable by following all java standards

A. Defined class as final
B. declared all fields as private and final
C. No setter method
D. No method changes the state of object
E. declared all method as final
F. Safer/defencieve copying of collection/ non mutable object fields.

These are the priliminary checkpoints I made when desigining immutable class.

But one question left, my object can still be modified by java reflection, am I right? Or is there any point I missed in the class?

Thanks in advance.

You can set a security manager and prevent objects from being modified via reflection. — Edwin Dalorzo, Oct 20 '12 at 03:45
see "How to limit setAccessible to only “legitimate” uses?" http://stackoverflow.com/questions/2481862/how-to-limit-setaccessible-to-only-legitimate-uses — ewernli, Oct 20 '12 at 03:51
@Bhesh,I have collection classes used in my class, along with declaring them as final, put extra measures to prevent any changes to it. — Satheesh Cheveri, Oct 20 '12 at 03:57
Aren't all methods of a final class implicitly final? Isn't it redundant to declare all methods as final? — mneri, Nov 30 '15 at 17:58

score 8 · Accepted Answer · answered Oct 20 '12 at 03:44

8

There's no hiding from reflection - even immutable classes are not immune. There is nothing you can do about it, though, so "cannot be modified through reflection" is not one of the criteria of immutability.

answered Oct 20 '12 at 03:44

Sergey Kalinichenko

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re: 'Nothing you can do about it', what about installing a SecurityManager to prevent reflection? – Grundlefleck Oct 20 '12 at 15:45

score 3 · Answer 2 · answered Oct 20 '12 at 05:20

Yes. Reflection can still access / change it. You can't really plan against that. If someone's altering your object with reflection, I would doubt the quality of code they're writing.

Immutable classes are fantastic to ensure thread safe applications. Immutable objects are ALWAYS thread safe. If you're looking for more great information, please read Effective Java. It's a MUST READ for any Java developer.

score 1 · Answer 3 · answered Oct 20 '12 at 03:44

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Yes, still it can be modified through reflection. Apart from that it seems you took required care to make it immutable.

answered Oct 20 '12 at 03:44

kosa

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Immutable class in java

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