Call for feedback -- switch expressions in JDK 12

[Manoj Palat]

Hi Alex,
Please find our feedback from Eclipse Java Dev.

   1)	For the break expression part we would be happy to have the
      “overloading” of break replaced by something else ? since this is
      already in the cards, no additional comment on this part.

   2)	Thanks to Remi Forax raising a bug in ecj [
      https://bugs.eclipse.org/bugs/show_bug.cgi?id=545716] and the
      following discussions, we believe that there could be a bug [in spec,
      javac as well as ecj] ? see this comment from Stephan Herrmann
      https://bugs.eclipse.org/bugs/show_bug.cgi?id=545716#c16 specifically
      for the findings. [@Alex: I am taking the liberty of pointing to the
      bug link rather than summarizing here since you have mentioned that a
      blog pointer should also be fine]

   Regards,

   Manoj

   Eclipse Java Dev, IBM




From:	Alex Buckley <alex.buckley at oracle.com>
To:	jdk-dev at openjdk.java.net
Date:	04/17/2019 11:23 PM
Subject:	Re: Call for feedback -- switch expressions in JDK 12
Sent by:	"jdk-dev" <jdk-dev-bounces at openjdk.java.net>



The feedback we're looking for is "I tried switch expressions in my code
and observed ...". For example:

https://urldefense.proofpoint.com/v2/url?u=https-3A__mail.openjdk.java.net_pipermail_amber-2Ddev_2019-2DMarch_004199.html&d=DwIFaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=A51zLdywEjS50U7u2UMWvsDIrUGEJ5IDXskL5MxIEjA&m=yINx0-noxNSSsm-dLx2P9YD7dvF6187FW7CStT07mp4&s=9at0fZB0bQpeEPI5L2IWbMSlUqcdgEsfF5944Rfjaxo&e=


If anyone is blogging about their experience with switch expressions,
feel free to share the URL here. For example, here's a great writeup of
using switch expressions in lambdas:

https://urldefense.proofpoint.com/v2/url?u=http-3A__minborgsjavapot.blogspot.com_2019_03_java-2D12-2Dmapping-2Dwith-2Dswitch-2Dexpressions.html&d=DwIFaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=A51zLdywEjS50U7u2UMWvsDIrUGEJ5IDXskL5MxIEjA&m=yINx0-noxNSSsm-dLx2P9YD7dvF6187FW7CStT07mp4&s=JE0ESlf3gLQJ5-QzuOU1uR_xMLngiysxuz0o948ZlW4&e=


Alex

On 4/16/2019 8:24 PM, Netroby wrote:
>     int numLetters = switch (day) {
>         case MONDAY, FRIDAY, SUNDAY -> 6,
>         case TUESDAY                -> 7,
>         case THURSDAY, SATURDAY     -> 8,
>         case WEDNESDAY              -> 9,
>         _ -> 0,
>     };
>
> Should we using  comma , instead of ;
>
> comma , means these cases the same switch.
>
> Another point, should we have an default match pattern ? using _ or
default
>
>
> idea from rust match
> ```rust
> fn main() {
>      let number = 13;
>      // TODO ^ Try different values for `number`
>
>      println!("Tell me about {}", number);
>      match number {
>          // Match a single value
>          1 => println!("One!"),
>          // Match several values
>          2 | 3 | 5 | 7 | 11 => println!("This is a prime"),
>          // Match an inclusive range
>          13...19 => println!("A teen"),
>          // Handle the rest of cases
>          _ => println!("Ain't special"),
>      }
>
>      let boolean = true;
>      // Match is an expression too
>      let binary = match boolean {
>          // The arms of a match must cover all the possible values
>          false => 0,
>          true => 1,
>          // TODO ^ Try commenting out one of these arms
>      };
>
>      println!("{} -> {}", boolean, binary);
> }
>
> ```
>
> Appreciate your time.
> ----------------------------
> Netroby
>
> Alex Buckley <alex.buckley at oracle.com> 于2019年4月17日周三 上午10:00写
道：
>>
>> An easy way to help move Java forward is to try out new features on real
>> code and share your experiences. We're asking for feedback on how you
>> use switch expressions, the new language feature in JDK 12:
>>
>>     int numLetters = switch (day) {
>>         case MONDAY, FRIDAY, SUNDAY -> 6;
>>         case TUESDAY                -> 7;
>>         case THURSDAY, SATURDAY     -> 8;
>>         case WEDNESDAY              -> 9;
>>     };
>>
>>     // Multiple labels per case (also allowed in switch statements)
>>     // No fallthrough with the -> form (also allowed in switch
statements)
>>
>> Do you find switch expressions useful? Is anything surprising? Did you
>> turn any switch statements into switch expressions? Please let us know
>> on this list, even if the answer is "Tried it. Works fine."
>>
>> To enable switch expressions in your environment:
>> - IntelliJ IDEA 2019.1
>>
https://urldefense.proofpoint.com/v2/url?u=https-3A__blog.jetbrains.com_idea_2019_02_java-2D12-2Dand-2Dintellij-2Didea_&d=DwIFaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=A51zLdywEjS50U7u2UMWvsDIrUGEJ5IDXskL5MxIEjA&m=yINx0-noxNSSsm-dLx2P9YD7dvF6187FW7CStT07mp4&s=-WsqDARpX60gLIBem_6IqycbQFRWL5bzkTNGVV322aU&e=

>> - Eclipse 4.11
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.eclipse.org_eclipse_news_4.11_jdt.php-23Java12&d=DwIFaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=A51zLdywEjS50U7u2UMWvsDIrUGEJ5IDXskL5MxIEjA&m=yINx0-noxNSSsm-dLx2P9YD7dvF6187FW7CStT07mp4&s=zClnCpCg04gt1vZS1Zz8j64uam6ZkpnGMVe4M5kCYd0&e=

>> - Apache NetBeans 11.0
>>
https://urldefense.proofpoint.com/v2/url?u=https-3A__cwiki.apache.org_confluence_pages_viewpage.action-3FpageId-3D103091452&d=DwIFaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=A51zLdywEjS50U7u2UMWvsDIrUGEJ5IDXskL5MxIEjA&m=yINx0-noxNSSsm-dLx2P9YD7dvF6187FW7CStT07mp4&s=5RLv6qs5qiU3r9dJ8KjnT4aPKRyz8hxXvNN0w5Z6x94&e=

>> - jshell in JDK 12  run with `--enable-preview`
>> - javac in JDK 12  run with `--release 12 --enable-preview`
>>
>> Alex