If we add this API, I like addListener(InvalidationListener, boolean) better than ensureListener().


On 2014-01-22 8:20 AM, Ali Ebrahimi wrote:
I suggest adding another overload for addListener method taking boolean
parameter  "duplicateAllowed" or "duplicateNotAllowed".

On Wed, Jan 22, 2014 at 3:00 PM, Richard Bair <richard.b...@oracle.com>wrote:

The default implementation (for Observable) would look like this:

public default void ensureListener(InvalidationListener listener) {

subclasses might do something more effective. The same would apply to
ObservableValue and ChangeListener and Observable[List|Set|Map] and
Well this would destroy the order! I expect listeners to be called in
the correct order not?
That’s a good point :-(

Why doing a remove and not simply check if the
listener has already been added?
Because there is no way to check, except in the implementation. From the
Observable interface level, there is no way to a) force all implementations
of the interface to implement the method correctly (without breaking source
compatibility anyway), or b) to provide a reasonable default implementation.

Maybe this is one of those things we can’t fix on the Observable interface
and just have to provide implementations of on our concrete properties.


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