I’ll offer this alternative: perhaps shorter method bodies obviate the need for explicit final vars.
Anthony > On Jun 18, 2019, at 10:30 AM, Ernest Burghardt <eburgha...@pivotal.io> wrote: > > +1 to auto-enforcement (if possible) post-consensus > > On Tue, Jun 18, 2019 at 8:33 AM Murtuza Boxwala <mboxw...@pivotal.io> wrote: > >> final in Java does not guarantee immutability. It would be AWESOME if it >> did but all it guarantees is that the variable cannot be reassigned. In >> most cases the variable points to an object’s location (memory address), so >> you can still call methods on it, e.g. >> >> final var = new Foo(); >> var.mutateState(); >> >> final variables like these are in no way thread safe. To make objects >> immutable, the objects themselves need to follow a pattern that guarantees >> that. Something like the ValueObject < >> https://martinfowler.com/bliki/ValueObject.html> pattern. >> >> Mutability may well be the enemy, but I don’t think this is the construct >> that gets us much/if any closer. >> >> In local variables and parameters final feels like noise to me, and in >> fact may make things more difficult to reason about, if we start assuming >> variables with final are thread safe. >> >> But I may be missing something. I am more curious to see how we come to >> consensus on something like this, because the worst outcome from all this >> will be to have some folks actively adding final and some actively removing >> it, which will add noise to PRs and to the code. And once we reach >> consensus, how do we enforce somethings like this? ./gradlew spA? >> >>> On Jun 17, 2019, at 8:55 PM, Jacob Barrett <jbarr...@pivotal.io> wrote: >>> >>> I too am in camp final too. You could say `final boolean useFinal = >> true`. For all the same reasons Bill stated below. >>> >>>> On Jun 17, 2019, at 5:33 PM, Bill Burcham <bburc...@pivotal.io> wrote: >>>> >>>> The final keyword is not redundant—quite the opposite—it's extremely >> valuable. >>>> >>>> Local variables are not, in general, final, unless you declare them as >> such. That being the case, it is not redundant to declare local variables >> "final". >>>> >>>> What the compiler will do for you, is _if_ it can ensure that a local >> variable (or method parameter) is never modified (after initialization) >> then that variable is treated as "effectively final". Variables that are >> explicitly declared final, or are determined to be "effectively final" may >> be referenced in lambdas. That's a nice thing. >>>> >>>> I would like to offer a counter-recommendation: final should be the >> default everywhere for fields, for method parameters (on classes, not on >> interfaces), and for local variables. >>>> >>>> Many benefits would accrue to us, should we adopt this default: >>>> >>>> 1. final fields must be initialized in a constructor and never mutated >> again. This makes reasoning about those fields easier. >>>> 2. classes that have all their fields final are immutable and hence >> easier to reason about: they can be passed between threads, for instance, >> with no need to protect from races >>>> 3. final method parameters can never be mutated, making them easier to >> reason about >>>> 4. final local variables can never be mutated, making them easier to >> reason about >>>> >>>> When final is the rule, non-final is the exception. Another way of >> saying that is that when final is the rule, mutability is the exception. >> That is as it should be. Mutability is the enemy. >>>> >>>> I have turned on a couple IntelliJ settings that make this the default >> for me. I encourage you to do the same: >>>> >>>> First there are these two "Code style issues" in the Java inspections: >>>> >>>> "Field may be 'final'" >>>> "Local variable or parameter can be final" >>>> >>>> >>>> >>>> Then there is this setting will cause newly-defined variables created >> via the "Extract variable" refactoring: >>>> >>>> If you select that check box (after selecting those inspections >> settings above), it'll declare the newly-introduced variable "final" and >> it'll remember the setting the next time you invoke "Extract variable" >> refactoring >>>> >>>> >> >>
