RFR: 8258777: SkinBase: add api to un-/register invalidation-/listChange listeners [v2]

[Kevin Rushforth]

On Wed, 24 Mar 2021 23:30:03 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

>> Jeanette Winzenburg has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fixed missing/incorrect @since tags in new api doc
>
> modules/javafx.controls/src/main/java/javafx/scene/control/SkinBase.java line 273:
> 
>> 271:      * @since 17
>> 272:      */
>> 273:     protected final Consumer<Observable> unregisterInvalidationListeners(Observable observable) {
> 
> Is `null` check on `observable` needed?

`unregisterInvalidationListeners` does the `null` check

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PR: https://git.openjdk.java.net/jfx/pull/409