On Wed, 15 Oct 2025 03:40:24 GMT, John Hendrikx <[email protected]> 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
