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From: =?UTF-8?Q?Arne_Vajh=c3=b8j?= <arne@vajhoej.dk>
Newsgroups: comp.lang.java.programmer
Subject: Re: Generics and downcasts
Date: Tue, 25 Apr 2017 19:54:31 -0400
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On 4/25/2017 4:35 PM, Eric Douglas wrote:
> On Tuesday, April 25, 2017 at 4:21:08 PM UTC-4, Arne Vajhøj wrote:
>> <quote> Like many myths about Java performance, the erroneous
>> belief that declaring classes or methods as final results in better
>> performance is widely held but rarely examined. The argument goes
>> that declaring a method or class as final means that the compiler
>> can inline method calls more aggressively, because it knows that at
>> run time this is definitely the version of the method that's going
>> to be called. But this is simply not true. Just because class X is
>> compiled against final class Y doesn't mean that the same version
>> of class Y will be loaded at run time. So the compiler cannot
>> inline such cross-class method calls safely, final or not. Only if
>> a method is private can the compiler inline it freely, and in that
>> case, the final keyword would be redundant. </quote>
>
> Eclipse Cleanup adds final modifiers all over the place.  I don't
> recall if these are supposed to help performance.  All I know is 3 of
> the purposes for final.  1) declaring a public, usually static
> constant variable 2) declaring a class that should never be extended
> and 3) declaring a variable in a class that needs to pass directly
> into something, like a SwingWorker.

There are reasons to use final. Just not performance optimization.

Arne