List Model Controls - The Definitive Guide to Java Swing - page 451

Or, if you want to work with all elements as an array, use either public Object[] toArray() or
public void copyInto(Object anArray[]) . You can also check for the existence of an element
within a model with methods such as public boolean contains(Object element) , public int
indexOf(Object element) , public int indexOf(Object element, int index) , public int
lastIndexOf(Object element) , and public int lastIndexOf(Object element, int index) .

Tip Once you're finished adding elements to the data model, it's a good idea to trim its length with public void
trimToSize() . This removes any extra preallocated space within the internal data structure. In addition, if you
know the size of the data model in advance, you can call public void ensureCapacity(int minCapacity) to
preallocate space. Both of these methods work only with DefaultListModel .

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ComboBoxModel Interface
The ComboBoxModel interface extends the ListModel interface. The key reason for this extension
is that the classes that implement the ComboBoxModel interface need to manage the selected
item internally through a selectedItem property, as shown by the interface definition.

public interface ComboBoxModel extends ListModel {
// Properties
public Object getSelectedItem();
public void setSelectedItem(Object anItem);
}

MutableComboBoxModel Interface
In addition to the ComboBoxModel interface, another data model interface,
MutableComboBoxModel , extends ComboBoxModel to make methods available to modify the
data model.

public interface MutableComboBoxModel extends ComboBoxModel {
// Other methods
public void addElement(Object obj);
public void insertElementAt(Object obj, int index);
public void removeElement(Object obj);
public void removeElementAt(int index);
}

The JComboBox component uses an implementation of this interface by default.

DefaultComboBoxModel Class
The DefaultComboBoxModel class extends the AbstractListModel class to provide an appropriate
data model for the JComboBox . Because of this extension, it inherits the managing of the
ListDataListener list.