RFR: 8091429: ObservableList<E>#setAll(int from, int to, Collection<? extends E> col)

[Michael Strauß]

On Wed, 15 Oct 2025 03:40:24 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

> This PR implements two new default methods on `ObservableList` to be able to replace elements at a given position or within a specified range.
> 
> Justification for this change is to allow an `ObservableList` to be bulk modified resulting in a single `ListChangeListener` call back.  In this way the callbacks don't observe the list changing its size from S to S-X back to S again(*). Currently the only way to bulk replace a range of items is to remove X items then add X items, resulting in two listener callbacks in between which the size of the list can be observed to change.
> 
> The other alternative is to call `set` individually for each item, which results in many change notifications.
> 
> With the addition of this PR, and the changes in `ModifiableObservableListBase`, replacing a range of items becomes a single change callback.
> 
> (*) The list may indeed change size still as plain `List` does not have `setAll` operations; size listeners may observe this, but it will no longer be observable from a `ListChangeListener` due to multiple separate callbacks.

modules/javafx.base/src/main/java/javafx/collections/ObservableList.java line 92:

> 90:      *
> 91:      * @param index the start index at which to replace elements, must be in
> 92:      *              {@code 0 .. size() - col.size()}

This seems to be an unnecessary limitation. It means that as a result of this operation, ~~the list can only be shorter, but not longer~~ the size of the list must stay the same. The `setAll(int, int, Collection)` overload doesn't have this limitation.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1937#discussion_r2432315088