Marking method parameter final, value of

Question

In this example, what value does declaring Object final offer?

private void doSomethingClever(final Object o) {

}

score 3 · Answer 1 · answered May 05 '12 at 01:56

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What this does is it allows someone else who comes along and visits your code to know the parameter cannot be changed. Resulting in a compilier error if they set a value.

answered May 05 '12 at 01:56

Justin

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score 2 · Accepted Answer · edited May 23 '17 at 10:34

2

That is to say that using it tells readers and the compiler that that parameter will not be modified in the method.

Useful Links:

edited May 23 '17 at 10:34

Community

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answered May 05 '12 at 01:57

Naveed

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Thanks Naveed. Good reference – James Raitsev May 05 '12 at 02:05

MByD · Answer 3 · 2012-05-05T02:01:21.197

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You will not be able to assign to o in the method.

It is very useful when having an inner class such as listener or some runnable accessing this local variable.

edited May 05 '12 at 02:01

answered May 05 '12 at 01:56

MByD

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score 0 · Answer 4 · edited May 12 '12 at 23:11

To be honest I don't really see the point of using final in method parameters. final will only guarantee that the variable will not be pointing to another object, not that the object itself will not be immutable... You can change the state of Object o, you just cant assign o to another object like B

o = new Object();

or

Object b = new Object();
o=b;

but invoking

o.doSomething();

is just fine. So why clutter the code with ugly final keywords everywhere??

As for performance optimization I believe that modern compilers will analyze and optimize the code even without the final keyword in method parameters. Would anyone care to correct me on this as I'm not 100% sure about that point!

Marking method parameter final, value of

4 Answers4