RFR: JDK-8304439: Subscription based listeners [v13]

[John Hendrikx]

On Thu, 13 Jul 2023 00:21:19 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

>> John Hendrikx has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix ObservableSubscriptionsTest
>
> modules/javafx.base/src/main/java/javafx/beans/Observable.java line 101:
> 
>> 99:      * {@code invalidationSubscriber} whenever it becomes invalid. If the same
>> 100:      * subscriber is subscribed more than once, then it will be notified more
>> 101:      * than once. That is, no check is made to ensure uniqueness.
> 
> Similar to the comments on `ObservableValue`:
> 
> Creates a {@code Subscription} on this {@code Observable} that calls the given
> {@code invalidationSubscriber}  whenever it becomes invalid. This {@code Subscription}
> is akin to an {@code InvalidationListener} without the {@code Observable} parameter.

Added this, but reworded as:

`The provided subscriber is akin ... `

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PR Review Comment: https://git.openjdk.org/jfx/pull/1069#discussion_r1263053110