Call for feedback -- enhanced switch

[Jeyvison Nascimento]

Oh, thanks Brian. Got it totally wrong before.

El mié., 6 mar. 2019 5:55, Brian Goetz <brian.goetz at oracle.com> escribió:

> Just to clarify my request — I was looking for feedback on the _actual
> experience of writing code with it_, now that a GA build is imminent and
> there is IDE support.
>
> People often ask how they can contribute to the process.  One of the
> easiest ways is to try out these new features _on real code_ and share your
> experiences.
>
> Sent from my MacBook Wheel
>
> On Mar 5, 2019, at 8:28 PM, Jeyvison Nascimento <jeynoronha at gmail.com>
> wrote:
>
> Hey all. I'd like to share a few impressions from what I saw about the
> Enhanced switch.
>
> The JEP is really good and it makes the code a lot cleaner. I don't know
> if we still have time to suggest something but I'd like to suggest three
> things to be added to it. I'm sorry if it was already discussed but I'm
> pretty new on this list.
>
> *Type Comparison when arg is Object*
>
> Imagine we are calculating an insurance risk based on the type of the
> vehicle we wanna get a quote. So we wanna cal different methods and perform
> different operations if this vehicle is a boat, a car or a bus.
>
> I know we can rely on String for that, adding the type as String attribute
> or relying on *.getClass().getName()),  but the former is error-prone and
> later is very repetitive.
> We can also use Enums for that, but again it becomes an instance attribute
> and there are situations when we cannot use Enums( trust me, it's a thing).
>
> We could have some code that looks like this:
>
> int insuranceRisk = switch (vehicle){
>     case Boat -> 3 * analyzeManufacturingDate(vehicle); //vehicle casted to Boat
>     case Bus -> 2 * vehicle.numberOfPassengers(); // vehicle casted to Bus.
>     case Car -> analyzeSeatBeltsAndTires(vehicle); // vehicle casted to Car.
>     default -> 0;
> };
>
>
> We compare the type of the instance arg and autocast it at the right of
> "case L".
>
> *Calling default value when no value is returned from expression.*
>
> TBH this one is not very clear to me if it's really necessary/good but
> I'll leave it here if you guys have something to say about this. In resume,
> there can be some situations when we wanna perform different operations but
> return the same value and it can be a little repetitive.
>
> We could have something like this:
>
> int taxes = switch(taxes_type){
>     case TaxesType.FEDERAL_TAXES -> voidLogFederalTaxes();
>     case TaxesType.STATE_TAXES -> intCalculateStateTaxes();
>     case TaxesType.CITY_TAXES ->  voidCallCityTaxesAPI();
>     default -> calculateCommonTaxes();
> };
>
>
> The first and third cases call a void method that performs a specific
> operation. Of course, I could make then break and return
> *calculateCommomTaxes()* but you can see that it can get repetitive(as in
> code duplication) over time.
>
> *Break to Break-with*
>
> A minor sugestion. * Break value* and * break-with* *value* doesn't seem
> very descriptive to me. Maybe *break-return value*?
>
>
> *Resume*
>
> In resume, all these suggestions are from someone that has no idea if it
> was already discussed or the implementation cost of it but i'd like to hear
> what you folks hate
> to say about it :)
>
> Thanks a lot.
>
> Em seg, 4 de mar de 2019 às 07:24, Ben Evans <
> benjamin.john.evans at gmail.com> escreveu:
>
>> Hi Brian,
>>
>> Can you explain the urgency here?
>>
>> If this is going to be a permanent feature as of Java 13, the deadline
>> for confirming that is surely months away, and I thought that one of
>> the points of Preview Features was that the promotion to permanent was
>> supposed to be a quick flick of the switch (no pun intended).
>>
>> On the other hand, Java 12 isn't even out yet! So no-one who isn't an
>> avid early adopter, or subscribed to this group (& I posit that we're
>> not exactly normal Java developers, for the most part) has tried this
>> feature in anger.
>>
>> As Martijn pointed out, this feature has just landed in the nightly
>> builds of IntelliJ - perhaps Trish or one of the other JetBrains folks
>> can give us an idea of how many downloads they see for the nightlies?
>> - that might give us some idea of how many developers have actually
>> tried out the feature (although, of course, they are still a
>> self-selecting early adopter group).
>>
>> Thanks,
>>
>> Ben
>>
>> On Fri, 1 Mar 2019 at 22:55, Brian Goetz <brian.goetz at oracle.com> wrote:
>> >
>> > We would like to promote enhanced switch to a permanent feature in Java
>> 13.  So far, the only change we are anticipating is:
>> >
>> >     - change “break value” to “break-with value”.
>> >
>> > This is the time for people to try it out on their codebases (there’s
>> even refactoring support in IDEA!) and provide feedback on what works, what
>> doesn’t, and what was surprising.
>> >
>> >
>>
>
>
> --
> Jeyvison Nascimento
>
>