do expression

[Remi Forax]

Hi Tagir, 
There already a syntax for that in Java, 
we are using it for lambda and switch, the arrow block syntax. 

static final String FIELD = -> { 
try { 
yield initializeField(); 
} 
catch(CheckedException e) { 
throw new RuntimeException(e); 
} 
}; 

Rémi 

> De: "Tagir Valeev" <amaembo at gmail.com>
> À: "amber-spec-experts" <amber-spec-experts at openjdk.java.net>
> Envoyé: Mardi 24 Mars 2020 03:23:10
> Objet: do expression

> Hello!

> Now we have a legal way to execute several statements within an expression,
> yielding the result with a yield statement. This could be done via `switch`
> expression.

> Sometimes it's desired to do this without any switch. One may abuse the switch
> expression feature writing `switch(0) { default -> { ... code block ending with
> 'yield' }}`.

> How about creating a special syntax for such kind of expression. It could look
> like `do { ... code block ending with 'yield' }`?

> E.g. consider:

> class X {
> static final String field;

> // now we are forced to split field declaration and initialization
> // also initializer could be long and it could be not evident that its main
> purpose
> // is to initialize the field
> static {
> try {
> field = initializeField();
> }
> catch(CheckedException e) {
> throw new RuntimeException(e);
> }
> }
> }

> Since Java 14 we can write

> class X {
> // field declaration and initialization in the same place: easier to navigate
> through code
> // though we are abusing the switch expression
> static final String field = switch(0) { default -> {
> try {
> yield initializeField();
> }
> catch(CheckedException e) {
> throw new RuntimeException(e);
> }
> }};
> }

> It could be like

> class X {
> // concise syntax. Now we know that the main block purpose
> // is to initialize the field
> static final String field = do {
> try {
> yield initializeField();
> }
> catch(CheckedException e) {
> throw new RuntimeException(e);
> }
> };
> }

> It's similar to Perl 'do BLOCK' expression
> [ https://perldoc.perl.org/functions/do.html |
> https://perldoc.perl.org/functions/do.html ]

> What do you think?

> With best regards,
> Tagir Valeev
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