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List:       openjdk-swing-dev
Subject:    <Swing Dev> 6179357: Generics: JList: Constructors & Model
From:       fbrunnerlist () gmx ! ch (Florian Brunner)
Date:       2009-02-26 21:25:03
Message-ID: 200902262225.03571.fbrunnerlist () gmx ! ch
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So, which approach do we take? I'm tending now more towards approach 1) but approach 2) would be 
fine for me, too? 

Pavel? Anyone else?

-Florian

Am Samstag, 21. Februar 2009 schrieb Florian Brunner:
> In the case of JComboBox I think it's not even possible to define something
> like:
>
>  class JComboBox<E>{
>  ComboBoxModel<? extends E> getModel();
>  setModel(ComboBoxModel<? extends E>);
>  }
>
> because JComboBox internally uses the ComboBoxModel.setSelectedItem method.
>
> So the question is what do you think is better:
>
> 1) To look at each component individually and try to make each as flexible
> as possible. So in the JList/ JComboBox case this would mean:
>
>  class JList<E>{
>  ListModel<? extends E> getModel();
>  setModel(ListModel<? extends E>);
>  }
>
> but
>
>  class JComboBox<E>{
>  ComboBoxModel<E> getModel();
>  setModel(ComboBoxModel<E>);
>  }
>
> 2) Make the interfaces as consistent as possible over all components.
> This would mean for the JList case to use somethink like:
>  class JList<E>{
>  ListModel<E> getModel();
>  setModel(ListModel<E>);
>  }
>
> This approach is slightly less flexible than the approach 1), but cases
> where one could benefit from approach 1) are probably rare and there are
> various work-arounds (like: wrapping the model/ use a common base class for
> the generic parameter/ use raw type/... )
>
> So what do you think? Approach 1) or 2)?
>
> -Florian
>
> Am Donnerstag, 19. Februar 2009 schrieb Florian Brunner:
> > Well, there is probably no big issue with JList, because the ListModel is
> > immutable.
> >
> > But when we add generics to JComboBox, which is similar to JList, the
> > situation is a bit more controversial, because the ComboBoxModel is
> > mutable.
> >
> > So if we have something like this:
> > class JComboBox<E>{
> > ComboBoxModel<? extends E> getModel();
> > setModel(ComboBoxModel<? extends E>);
> > }
> >
> > then something like this is not possible:
> > JComboBox<Foo> cb = new JComboBox<Foo>(...);
> > ...
> > Foo foo;
> > ComboBoxModel<? extends Foo> model = cb.getModel();
> > model.setSelectedItem(foo); -> compile time error
> >
> > You would need to do an unchecked (-> not type-safe) cast first:
> > ComboBoxModel<Foo> model = (ComboBoxModel<Foo>) cb.getModel();
> >
> > And type-safty is what generics is all about.
> >
> > -Florian
> >
> > Am Dienstag, 3. Februar 2009 schrieb Pavel Porvatov:
> > > Hi Florian,
> > >
> > > > ----------------------------------------
> > > >
> > > > public JList(ListModel dataModel)
> > > >
> > > > {
> > > >
> > > > if (dataModel == null) {
> > > >
> > > > throw new IllegalArgumentException("dataModel must be non null");
> > > >
> > > > }
> > > >
> > > > // Register with the ToolTipManager so that tooltips from the
> > > >
> > > > // renderer show through.
> > > >
> > > > ToolTipManager toolTipManager = ToolTipManager.sharedInstance();
> > > >
> > > > toolTipManager.registerComponent(this);
> > > >
> > > > layoutOrientation = VERTICAL;
> > > >
> > > > this.dataModel = dataModel;
> > > >
> > > > selectionModel = createSelectionModel();
> > > >
> > > > setAutoscrolls(true);
> > > >
> > > > setOpaque(true);
> > > >
> > > > updateUI();
> > > >
> > > > }
> > > >
> > > > --->
> > > >
> > > > public JList(ListModel<E> dataModel)
> > > >
> > > > {
> > > >
> > > > if (dataModel == null) {
> > > >
> > > > throw new IllegalArgumentException("dataModel must be non null");
> > > >
> > > > }
> > > >
> > > > // Register with the ToolTipManager so that tooltips from the
> > > >
> > > > // renderer show through.
> > > >
> > > > ToolTipManager toolTipManager = ToolTipManager.sharedInstance();
> > > >
> > > > toolTipManager.registerComponent(this);
> > > >
> > > > layoutOrientation = VERTICAL;
> > > >
> > > > this.dataModel = dataModel;
> > > >
> > > > selectionModel = createSelectionModel();
> > > >
> > > > setAutoscrolls(true);
> > > >
> > > > setOpaque(true);
> > > >
> > > > updateUI();
> > > >
> > > > }
> > > >
> > > > We could define the signature also like this:
> > > >
> > > > public JList(ListModel<? extends E> dataModel)
> > > >
> > > > but then we would have to define the dataModel-field also with:
> > > >
> > > > private ListModel<? extends E> dataModel
> > > >
> > > > as well as the model-property. I don't think this would be a good
> > > > idea and thus define the signature as:
> > > >
> > > > public JList(ListModel<E> dataModel)
> > > >
> > > > What do you think?
> > >
> > > Why do you think that "private ListModel<? extends E> dataModel" is not
> > > a very good idea?
> > >
> > > Regards, Pavel




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