Hi Florian,
Hi Pavel,
I start here a new thread for the "get/setSelectedItem(Object) methods of JComboBox and
ComboBoxModel" discussion.
After further analysis of the code and your sample application I think we can and should generify
the get/setSelectedItem(Object) methods of JComboBox and ComboBoxModel.
Yes, the Javadoc says that JComboBox/ ComboBoxModel supports selected values not managed by the
underlying list model. But this does not prohibit to optionally limit the type by using generics und
thus to increase type safety.
If you need to allow other types from editor than the ones in the list model,
you still can use:
JComboBox<Object> (or JComboBox, but this is not recommended)
So there should be no backward compatibility problem.
When using a JComboBox, usually you are interested in the selected value and since you want to do
something with it you expect it to have some specific type. So if we generify the
get/setSelectedItem(Object), you can profit from that in most cases.
Even in cases where you have an initial text in an editable combo box you can profit from that, if
you use a "null" value as the selected value, which according to the API is used for "no selection",
and a custom editor for rendering that null value. (see attachement; I used your sample application
as a base; delete the text to set the selected value to null again).
I agree that generification of the get/setSelectedItem(Object) methods
will be useful. But than we will have another generification
disadvantage. I tried to summarize benefits of two solutions below.
*Generified get/setSelectedItem:*
a. Simplified usage read-only comboboxes or non read-only comboboxes
with special editor
b. Disadvantage: if you use generified editable combobox *without*
editor then ClassCastException will be thrown in runtime
*Not generified get/setSelectedItem:*
a. A possibility to generify the javax.swing.JComboBox#dataModel as
ComboBoxModel<? extends E>. It give us more flexible usage of ComboBox:
ComboBoxModel<Integer> cbModel = ....;
JComboBox<Number> cb = new JComboBox<Number>(cbModel);
Note that it's the main benefit that forced us to suggest not generified
methods
b. To use not read-only combobox with generified model
So I believe that not generified get/setSelectedItem methods give more
benefits and less disadvantages.
What do you think about that?
Regards, Pavel
