RFR: 8274771: Map, FlatMap and OrElse fluent bindings for ObservableValue [v11]

[John Hendrikx]

On Fri, 18 Mar 2022 11:12:55 GMT, Tom Schindl <tschindl at openjdk.org> wrote:

>> John Hendrikx has updated the pull request incrementally with five additional commits since the last revision:
>> 
>>  - Reword flat map docs a bit and fixed a link
>>  - Add missing javadoc tags
>>  - Clean up docs in Subscription
>>  - Fix code blocks
>>  - Add line feed at last line where it was missing
>
> modules/javafx.base/src/main/java/com/sun/javafx/binding/Subscription.java line 57:
> 
>> 55:      * Cancels this subscription.
>> 56:      */
>> 57:     void unsubscribe();
> 
> to me `unsubscribe` feels not natural, I'm not unsubscribing a `Subscription` but I'm eg disposing it, hence to me `dispose` would feel better but I'm not a native speaker.
> 
> Another pattern I see often is that I store a subscription in a field and recreate it under certain conditions:
> 
> 
> private Subscription mySubscription;
> 
> void refresh() {
>    if( this.mySubscription != null ) {
>      this.mySubscription.dispos();
>    }
>    this.mySubscription = ....
> }
> 
> 
> if Subscription would provide
> 
> ```java 
> static void dispose(Subscription subscription) {
>   if( subscription != null ) {
>     subscription.dispose();
>   }
> }
> 
> 
> this would safe the user a null-check.

This API is not going to be public for now, so we still have some time to work out the details.  Another option would be to use `cancel` instead of `unsubscribe` or `dispose` (an internal class in the JDK uses `cancel`, reactfx uses `unsubcribe`).  

    Subscription.dispose(subscription);

I'm not sure how I feel about a helper method like that to do a `null` check; I feel that `null` checks are the callers responsibility (in almost all situations).  It is also not really OO, it feels like `void *x = malloc(1000)` and `free(x)` instead of getting an object and calling `free` on the object.

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PR: https://git.openjdk.java.net/jfx/pull/675