JComboBox (Java 2 Platform SE v1.4.1_"07")

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JavaTM 2 Platform
Std. Ed. v1.4.1_"07"

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## javax.swing
Class JComboBox

    java.lang.Object
      |
      +--java.awt.Component
            |
            +--java.awt.Container
                  |
                  +--javax.swing.JComponent
                        |
                        +--javax.swing.JComboBox

All Implemented Interfaces:
  Accessible, ActionListener, EventListener, ImageObserver, ItemSelectable, ListDataListener, MenuContainer, Serializable

public class JComboBox
extends JComponent
implements ItemSelectable, ListDataListener, ActionListener, Accessible

A component that combines a button or editable field and a drop-down list. The user can select a value from the drop-down list, which appears at the user's request. If you make the combo box editable, then the combo box includes an editable field into which the user can type a value.

For the keyboard keys used by this component in the standard Look and Feel (L&F) renditions, see the `JComboBox` key assignments.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeansTM has been added to the `java.beans` package. Please see `XMLEncoder`.

See How to Use Combo Boxes in The Java Tutorial for further information.

See Also:
  `ComboBoxModel`, `DefaultComboBoxModel`

Nested Class Summary
`protected class` | `JComboBox.AccessibleJComboBox` This class implements accessibility support for the `JComboBox` class.
`static interface` | `JComboBox.KeySelectionManager` The interface that defines a `KeySelectionManager`.

Nested classes inherited from class javax.swing.JComponent
``

Nested classes inherited from class java.awt.Container
``

Nested classes inherited from class java.awt.Component
`Component.BltBufferStrategy, Component.FlipBufferStrategy`

Field Summary
`protected String` | `actionCommand` This protected field is implementation specific.
`protected ComboBoxModel` | `dataModel` This protected field is implementation specific.
`protected ComboBoxEditor` | `editor` This protected field is implementation specific.
`protected boolean` | `isEditable` This protected field is implementation specific.
`protected JComboBox.KeySelectionManager` | `keySelectionManager` This protected field is implementation specific.
`protected boolean` | `lightWeightPopupEnabled` This protected field is implementation specific.
`protected int` | `maximumRowCount` This protected field is implementation specific.
`protected ListCellRenderer` | `renderer` This protected field is implementation specific.
`protected Object` | `selectedItemReminder` This protected field is implementation specific.

Fields inherited from class javax.swing.JComponent
`accessibleContext, listenerList, TOOL_TIP_TEXT_KEY, ui, UNDEFINED_CONDITION, WHEN_ANCESTOR_OF_FOCUSED_COMPONENT, WHEN_FOCUSED, WHEN_IN_FOCUSED_WINDOW`

Fields inherited from class java.awt.Component
`BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT`

Fields inherited from interface java.awt.image.ImageObserver
`ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH`

Constructor Summary
`JComboBox()` Creates a `JComboBox` with a default data model.
`JComboBox(ComboBoxModel aModel)` Creates a `JComboBox` that takes it's items from an existing `ComboBoxModel`.
`JComboBox(Object[] items)` Creates a `JComboBox` that contains the elements in the specified array.
`JComboBox(Vector items)` Creates a `JComboBox` that contains the elements in the specified Vector.

Method Summary
`void` | `actionPerformed(ActionEvent e)` This method is public as an implementation side effect.
`void` | `addActionListener(ActionListener l)` Adds an `ActionListener`.
`void` | `addItem(Object anObject)` Adds an item to the item list.
`void` | `addItemListener(ItemListener aListener)` Adds an `ItemListener`.
`void` | `addPopupMenuListener(PopupMenuListener l)` Adds a `PopupMenu` listener which will listen to notification messages from the popup portion of the combo box.
`void` | `configureEditor(ComboBoxEditor anEditor, Object anItem)` Initializes the editor with the specified item.
`protected void` | `configurePropertiesFromAction(Action a)` Factory method which sets the `ActionEvent` source's properties according to values from the `Action` instance.
`void` | `contentsChanged(ListDataEvent e)` This method is public as an implementation side effect.
`protected PropertyChangeListener` | `createActionPropertyChangeListener(Action a)` Factory method which creates the `PropertyChangeListener` used to update the `ActionEvent` source as properties change on its `Action` instance.
`protected JComboBox.KeySelectionManager` | `createDefaultKeySelectionManager()` Returns an instance of the default key-selection manager.
`protected void` | `fireActionEvent()` Notifies all listeners that have registered interest for notification on this event type.
`protected void` | `fireItemStateChanged(ItemEvent e)` Notifies all listeners that have registered interest for notification on this event type.
`void` | `firePopupMenuCanceled()` Notifies `PopupMenuListener`s that the popup portion of the combo box has been canceled.
`void` | `firePopupMenuWillBecomeInvisible()` Notifies `PopupMenuListener`s that the popup portion of the combo box has become invisible.
`void` | `firePopupMenuWillBecomeVisible()` Notifies `PopupMenuListener`s that the popup portion of the combo box will become visible.
`AccessibleContext` | `getAccessibleContext()` Gets the AccessibleContext associated with this JComboBox.
`Action` | `getAction()` Returns the currently set `Action` for this `ActionEvent` source, or `null` if no `Action` is set.
`String` | `getActionCommand()` Returns the action command that is included in the event sent to action listeners.
`ActionListener[]` | `getActionListeners()` Returns an array of all the `ActionListener`s added to this JComboBox with addActionListener().
`ComboBoxEditor` | `getEditor()` Returns the editor used to paint and edit the selected item in the `JComboBox` field.
`Object` | `getItemAt(int index)` Returns the list item at the specified index.
`int` | `getItemCount()` Returns the number of items in the list.
`ItemListener[]` | `getItemListeners()` Returns an array of all the `ItemListener`s added to this JComboBox with addItemListener().
`JComboBox.KeySelectionManager` | `getKeySelectionManager()` Returns the list's key-selection manager.
`int` | `getMaximumRowCount()` Returns the maximum number of items the combo box can display without a scrollbar
`ComboBoxModel` | `getModel()` Returns the data model currently used by the `JComboBox`.
`PopupMenuListener[]` | `getPopupMenuListeners()` Returns an array of all the `PopupMenuListener`s added to this JComboBox with addPopupMenuListener().
`Object` | `getPrototypeDisplayValue()` Returns the "prototypical display" value - an Object used for the calculation of the display height and width.
`ListCellRenderer` | `getRenderer()` Returns the renderer used to display the selected item in the `JComboBox` field.
`int` | `getSelectedIndex()` Returns the first item in the list that matches the given item.
`Object` | `getSelectedItem()` Returns the current selected item.
`Object[]` | `getSelectedObjects()` Returns an array containing the selected item.
`ComboBoxUI` | `getUI()` Returns the L&F object that renders this component.
`String` | `getUIClassID()` Returns the name of the L&F class that renders this component.
`void` | `hidePopup()` Causes the combo box to close its popup window.
`void` | `insertItemAt(Object anObject, int index)` Inserts an item into the item list at a given index.
`protected void` | `installAncestorListener()`
`void` | `intervalAdded(ListDataEvent e)` This method is public as an implementation side effect.
`void` | `intervalRemoved(ListDataEvent e)` This method is public as an implementation side effect.
`boolean` | `isEditable()` Returns true if the `JComboBox` is editable.
`boolean` | `isLightWeightPopupEnabled()` Gets the value of the `lightWeightPopupEnabled` property.
`boolean` | `isPopupVisible()` Determines the visibility of the popup.
`protected String` | `paramString()` Returns a string representation of this `JComboBox`.
`void` | `processKeyEvent(KeyEvent e)` Handles `KeyEvent`s, looking for the Tab key.
`void` | `removeActionListener(ActionListener l)` Removes an `ActionListener`.
`void` | `removeAllItems()` Removes all items from the item list.
`void` | `removeItem(Object anObject)` Removes an item from the item list.
`void` | `removeItemAt(int anIndex)` Removes the item at `anIndex` This method works only if the `JComboBox` uses a mutable data model.
`void` | `removeItemListener(ItemListener aListener)` Removes an `ItemListener`.
`void` | `removePopupMenuListener(PopupMenuListener l)` Removes a `PopupMenuListener`.
`protected void` | `selectedItemChanged()` This protected method is implementation specific.
`boolean` | `selectWithKeyChar(char keyChar)` Selects the list item that corresponds to the specified keyboard character and returns true, if there is an item corresponding to that character.
`void` | `setAction(Action a)` Sets the `Action` for the `ActionEvent` source.
`void` | `setActionCommand(String aCommand)` Sets the action command that should be included in the event sent to action listeners.
`void` | `setEditable(boolean aFlag)` Determines whether the `JComboBox` field is editable.
`void` | `setEditor(ComboBoxEditor anEditor)` Sets the editor used to paint and edit the selected item in the `JComboBox` field.
`void` | `setEnabled(boolean b)` Enables the combo box so that items can be selected.
`void` | `setKeySelectionManager(JComboBox.KeySelectionManager aManager)` Sets the object that translates a keyboard character into a list selection.
`void` | `setLightWeightPopupEnabled(boolean aFlag)` Sets the `lightWeightPopupEnabled` property, which provides a hint as to whether or not a lightweight `Component` should be used to contain the `JComboBox`, versus a heavyweight `Component` such as a `Panel` or a `Window`.
`void` | `setMaximumRowCount(int count)` Sets the maximum number of rows the `JComboBox` displays.
`void` | `setModel(ComboBoxModel aModel)` Sets the data model that the `JComboBox` uses to obtain the list of items.
`void` | `setPopupVisible(boolean v)` Sets the visibility of the popup.
`void` | `setPrototypeDisplayValue(Object prototypeDisplayValue)` Sets the prototype display value used to calculate the size of the display for the UI portion.
`void` | `setRenderer(ListCellRenderer aRenderer)` Sets the renderer that paints the list items and the item selected from the list in the JComboBox field.
`void` | `setSelectedIndex(int anIndex)` Selects the item at index `anIndex`.
`void` | `setSelectedItem(Object anObject)` Sets the selected item in the combo box display area to the object in the argument.
`void` | `setUI(ComboBoxUI ui)` Sets the L&F object that renders this component.
`void` | `showPopup()` Causes the combo box to display its popup window.
`void` | `updateUI()` Resets the UI property to a value from the current look and feel.

Methods inherited from class javax.swing.JComponent
`addAncestorListener, addNotify, addPropertyChangeListener, addPropertyChangeListener, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, disable, enable, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getActionMap, getAlignmentX, getAlignmentY, getAncestorListeners, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getConditionForKeyStroke, getDebugGraphicsOptions, getDefaultLocale, getGraphics, getHeight, getInputMap, getInputMap, getInputVerifier, getInsets, getInsets, getListeners, getLocation, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPreferredSize, getPropertyChangeListeners, getPropertyChangeListeners, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getTransferHandler, getVerifyInputWhenFocusTarget, getVetoableChangeListeners, getVisibleRect, getWidth, getX, getY, grabFocus, isDoubleBuffered, isLightweightComponent, isManagingFocus, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isOptimizedDrawingEnabled, isPaintingTile, isPreferredSizeSet, isRequestFocusEnabled, isValidateRoot, paint, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, print, printAll, printBorder, printChildren, printComponent, processComponentKeyEvent, processKeyBinding, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setActionMap, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setBorder, setDebugGraphicsOptions, setDefaultLocale, setDoubleBuffered, setFont, setForeground, setInputMap, setInputVerifier, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setTransferHandler, setUI, setVerifyInputWhenFocusTarget, setVisible, unregisterKeyboardAction, update`

Methods inherited from class java.awt.Container
`add, add, add, add, add, addContainerListener, addImpl, applyComponentOrientation, areFocusTraversalKeysSet, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getContainerListeners, getFocusTraversalKeys, getFocusTraversalPolicy, getLayout, insets, invalidate, isAncestorOf, isFocusCycleRoot, isFocusCycleRoot, isFocusTraversalPolicySet, layout, list, list, locate, minimumSize, paintComponents, preferredSize, printComponents, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, setFocusCycleRoot, setFocusTraversalKeys, setFocusTraversalPolicy, setLayout, transferFocusBackward, transferFocusDownCycle, validate, validateTree`

Methods inherited from class java.awt.Component
`action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, bounds, checkImage, checkImage, coalesceEvents, contains, createImage, createImage, createVolatileImage, createVolatileImage, disableEvents, dispatchEvent, enable, enableEvents, enableInputMethods, getBackground, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphicsConfiguration, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocale, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMouseWheelListeners, getName, getParent, getPeer, getSize, getToolkit, getTreeLock, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, isBackgroundSet, isCursorSet, isDisplayable, isEnabled, isFocusable, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processMouseEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, repaint, repaint, repaint, resize, resize, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setFocusable, setFocusTraversalKeysEnabled, setIgnoreRepaint, setLocale, setLocation, setLocation, setName, setSize, setSize, show, show, size, toString, transferFocus, transferFocusUpCycle`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

### dataModel

    protected ComboBoxModel dataModel

  This protected field is implementation specific. Do not access directly or override. Use the accessor methods instead.

  See Also:
    `getModel()`, `setModel(javax.swing.ComboBoxModel)`

### renderer

    protected ListCellRenderer renderer

  This protected field is implementation specific. Do not access directly or override. Use the accessor methods instead.

  See Also:
    `getRenderer()`, `setRenderer(javax.swing.ListCellRenderer)`

### editor

    protected ComboBoxEditor editor

  This protected field is implementation specific. Do not access directly or override. Use the accessor methods instead.

  See Also:
    `getEditor()`, `setEditor(javax.swing.ComboBoxEditor)`

### maximumRowCount

    protected int maximumRowCount

  This protected field is implementation specific. Do not access directly or override. Use the accessor methods instead.

  See Also:
    `getMaximumRowCount()`, `setMaximumRowCount(int)`

### isEditable

    protected boolean isEditable

  This protected field is implementation specific. Do not access directly or override. Use the accessor methods instead.

  See Also:
    `isEditable`, `setEditable(boolean)`

### keySelectionManager

    protected JComboBox.KeySelectionManager keySelectionManager

  This protected field is implementation specific. Do not access directly or override. Use the accessor methods instead.

  See Also:
    `setKeySelectionManager(javax.swing.JComboBox.KeySelectionManager)`, `getKeySelectionManager()`

### actionCommand

    protected String actionCommand

  This protected field is implementation specific. Do not access directly or override. Use the accessor methods instead.

  See Also:
    `setActionCommand(java.lang.String)`, `getActionCommand()`

### lightWeightPopupEnabled

    protected boolean lightWeightPopupEnabled

  This protected field is implementation specific. Do not access directly or override. Use the accessor methods instead.

  See Also:
    `setLightWeightPopupEnabled(boolean)`, `isLightWeightPopupEnabled()`

### selectedItemReminder

    protected Object selectedItemReminder

  This protected field is implementation specific. Do not access directly or override.

Constructor Detail

### JComboBox

    public JComboBox(ComboBoxModel aModel)

  Creates a `JComboBox` that takes it's items from an existing `ComboBoxModel`. Since the `ComboBoxModel` is provided, a combo box created using this constructor does not create a default combo box model and may impact how the insert, remove and add methods behave.

Parameters:
  `aModel` - the `ComboBoxModel` that provides the displayed list of items
See Also:
  `DefaultComboBoxModel`

### JComboBox

    public JComboBox(Object[] items)

  Creates a `JComboBox` that contains the elements in the specified array. By default the first item in the array (and therefore the data model) becomes selected.

Parameters:
  `items` - an array of objects to insert into the combo box
See Also:
  `DefaultComboBoxModel`

### JComboBox

    public JComboBox(Vector items)

  Creates a `JComboBox` that contains the elements in the specified Vector. By default the first item in the vector and therefore the data model) becomes selected.

Parameters:
  `items` - an array of vectors to insert into the combo box
See Also:
  `DefaultComboBoxModel`

### JComboBox

    public JComboBox()

  Creates a `JComboBox` with a default data model. The default data model is an empty list of objects. Use `addItem` to add items. By default the first item in the data model becomes selected.

See Also:
  `DefaultComboBoxModel`

Method Detail

### installAncestorListener

    protected void installAncestorListener()

### setUI

    public void setUI(ComboBoxUI ui)

  Sets the L&F object that renders this component.

  Parameters:
    `ui` - the `ComboBoxUI` L&F object
  See Also:
    `UIDefaults.getUI(javax.swing.JComponent)`

### updateUI

    public void updateUI()

  Resets the UI property to a value from the current look and feel.

  Overrides:
    `updateUI` in class `JComponent`
  See Also:
    `JComponent.updateUI()`

### getUIClassID

    public String getUIClassID()

  Returns the name of the L&F class that renders this component.

  Overrides:
    `getUIClassID` in class `JComponent`
  Returns:
    the string "ComboBoxUI"
  See Also:
    `JComponent.getUIClassID()`, `UIDefaults.getUI(javax.swing.JComponent)`

### getUI

    public ComboBoxUI getUI()

  Returns the L&F object that renders this component.

  Returns:
    the ComboBoxUI object that renders this component

### setModel

    public void setModel(ComboBoxModel aModel)

  Sets the data model that the `JComboBox` uses to obtain the list of items.

  Parameters:
    `aModel` - the `ComboBoxModel` that provides the displayed list of items

### getModel

    public ComboBoxModel getModel()

  Returns the data model currently used by the `JComboBox`.

  Returns:
    the `ComboBoxModel` that provides the displayed list of items

### setLightWeightPopupEnabled

    public void setLightWeightPopupEnabled(boolean aFlag)

  Sets the `lightWeightPopupEnabled` property, which provides a hint as to whether or not a lightweight `Component` should be used to contain the `JComboBox`, versus a heavyweight `Component` such as a `Panel` or a `Window`. The decision of lightweight versus heavyweight is ultimately up to the `JComboBox`. Lightweight windows are more efficient than heavyweight windows, but lightweight and heavyweight components do not mix well in a GUI. If your application mixes lightweight and heavyweight components, you should disable lightweight popups. The default value for the `lightWeightPopupEnabled` property is `true`, unless otherwise specified by the look and feel. Some look and feels always use heavyweight popups, no matter what the value of this property.

  See the article Mixing Heavy and Light Components on The Swing Connection This method fires a property changed event.

  Parameters:
    `aFlag` - if `true`, lightweight popups are desired

### isLightWeightPopupEnabled

    public boolean isLightWeightPopupEnabled()

  Gets the value of the `lightWeightPopupEnabled` property.

  Returns:
    the value of the `lightWeightPopupEnabled` property
  See Also:
    `setLightWeightPopupEnabled(boolean)`

### setEditable

    public void setEditable(boolean aFlag)

  Determines whether the `JComboBox` field is editable. An editable `JComboBox` allows the user to type into the field or selected an item from the list to initialize the field, after which it can be edited. (The editing affects only the field, the list item remains intact.) A non editable `JComboBox` displays the selected item in the field, but the selection cannot be modified.

  Parameters:
    `aFlag` - a boolean value, where true indicates that the field is editable

### isEditable

    public boolean isEditable()

  Returns true if the `JComboBox` is editable. By default, a combo box is not editable.

  Returns:
    true if the `JComboBox` is editable, else false

### setMaximumRowCount

    public void setMaximumRowCount(int count)

  Sets the maximum number of rows the `JComboBox` displays. If the number of objects in the model is greater than count, the combo box uses a scrollbar.

  Parameters:
    `count` - an integer specifying the maximum number of items to display in the list before using a scrollbar

### getMaximumRowCount

    public int getMaximumRowCount()

  Returns the maximum number of items the combo box can display without a scrollbar

  Returns:
    an integer specifying the maximum number of items that are displayed in the list before using a scrollbar

### setRenderer

    public void setRenderer(ListCellRenderer aRenderer)

  Sets the renderer that paints the list items and the item selected from the list in the JComboBox field. The renderer is used if the JComboBox is not editable. If it is editable, the editor is used to render and edit the selected item.

  The default renderer displays a string or an icon. Other renderers can handle graphic images and composite items.

  To display the selected item, `aRenderer.getListCellRendererComponent` is called, passing the list object and an index of -1.

  Parameters:
    `aRenderer` - the `ListCellRenderer` that displays the selected item
  See Also:
    `setEditor(javax.swing.ComboBoxEditor)`

### getRenderer

    public ListCellRenderer getRenderer()

  Returns the renderer used to display the selected item in the `JComboBox` field.

  Returns:
    the `ListCellRenderer` that displays the selected item.

### setEditor

    public void setEditor(ComboBoxEditor anEditor)

  Sets the editor used to paint and edit the selected item in the `JComboBox` field. The editor is used only if the receiving `JComboBox` is editable. If not editable, the combo box uses the renderer to paint the selected item.

  Parameters:
    `anEditor` - the `ComboBoxEditor` that displays the selected item
  See Also:
    `setRenderer(javax.swing.ListCellRenderer)`

### getEditor

    public ComboBoxEditor getEditor()

  Returns the editor used to paint and edit the selected item in the `JComboBox` field.

  Returns:
    the `ComboBoxEditor` that displays the selected item

### setSelectedItem

    public void setSelectedItem(Object anObject)

  Sets the selected item in the combo box display area to the object in the argument. If `anObject` is in the list, the display area shows `anObject` selected.

  If `anObject` is not in the list and the combo box is uneditable, it will not change the current selection. For editable combo boxes, the selection will change to `anObject`.

  If this constitutes a change in the selected item, `ItemListener`s added to the combo box will be notified with one or two `ItemEvent`s. If there is a current selected item, an `ItemEvent` will be fired and the state change will be `ItemEvent.DESELECTED`. If `anObject` is in the list and is not currently selected then an `ItemEvent` will be fired and the state change will be `ItemEvent.SELECTED`.

  `ActionListener`s added to the combo box will be notified with an `ActionEvent` when this method is called.

  Parameters:
    `anObject` - the list object to select; use `null` to clear the selection

### getSelectedItem

    public Object getSelectedItem()

  Returns the current selected item.

  If the combo box is editable, then this value may not have been added to the combo box with `addItem`, `insertItemAt` or the data constructors.

  Returns:
    the current selected Object
  See Also:
    `setSelectedItem(java.lang.Object)`

### setSelectedIndex

    public void setSelectedIndex(int anIndex)

  Selects the item at index `anIndex`.

  Parameters:
    `anIndex` - an integer specifying the list item to select, where 0 specifies the first item in the list and -1 indicates no selection
  Throws:
    `IllegalArgumentException` - if `anIndex` < -1 or `anIndex` is greater than or equal to size

### getSelectedIndex

    public int getSelectedIndex()

  Returns the first item in the list that matches the given item. The result is not always defined if the `JComboBox` allows selected items that are not in the list. Returns -1 if there is no selected item or if the user specified an item which is not in the list.

  Returns:
    an integer specifying the currently selected list item, where 0 specifies the first item in the list; or -1 if no item is selected or if the currently selected item is not in the list

### getPrototypeDisplayValue

    public Object getPrototypeDisplayValue()

  Returns the "prototypical display" value - an Object used for the calculation of the display height and width.

  Returns:
    the value of the `prototypeDisplayValue` property
  Since:
    1.4
  See Also:
    `setPrototypeDisplayValue(java.lang.Object)`

### setPrototypeDisplayValue

    public void setPrototypeDisplayValue(Object prototypeDisplayValue)

  Sets the prototype display value used to calculate the size of the display for the UI portion.

  If a prototype display value is specified, the preferred size of the combo box is calculated by configuring the renderer with the prototype display value and obtaining its preferred size. Specifying the preferred display value is often useful when the combo box will be displaying large amounts of data. If no prototype display value has been specified, the renderer must be configured for each value from the model and its preferred size obtained, which can be relatively expensive.

  Parameters:
    `prototypeDisplayValue` -
  Since:
    1.4
  See Also:
    `getPrototypeDisplayValue()`

### addItem

    public void addItem(Object anObject)

  Adds an item to the item list. This method works only if the `JComboBox` uses a mutable data model.

  Warning: Focus and keyboard navigation problems may arise if you add duplicate String objects. A workaround is to add new objects instead of String objects and make sure that the toString() method is defined. For example:

         comboBox.addItem(makeObj("Item 1"));
         comboBox.addItem(makeObj("Item 1"));
         ...
         private Object makeObj(final String item)  {
           return new Object() { public String toString() { return item; } };
         }

  Parameters:
    `anObject` - the Object to add to the list
  See Also:
    `MutableComboBoxModel`

### insertItemAt

    public void insertItemAt(Object anObject,
                             int index)

  Inserts an item into the item list at a given index. This method works only if the `JComboBox` uses a mutable data model.

  Parameters:
    `anObject` - the `Object` to add to the list
    `index` - an integer specifying the position at which to add the item
  See Also:
    `MutableComboBoxModel`

### removeItem

    public void removeItem(Object anObject)

  Removes an item from the item list. This method works only if the `JComboBox` uses a mutable data model.

  Parameters:
    `anObject` - the object to remove from the item list
  See Also:
    `MutableComboBoxModel`

### removeItemAt

    public void removeItemAt(int anIndex)

  Removes the item at `anIndex` This method works only if the `JComboBox` uses a mutable data model.

  Parameters:
    `anIndex` - an int specifying the index of the item to remove, where 0 indicates the first item in the list
  See Also:
    `MutableComboBoxModel`

### removeAllItems

    public void removeAllItems()

  Removes all items from the item list.

### showPopup

    public void showPopup()

  Causes the combo box to display its popup window.

  See Also:
    `setPopupVisible(boolean)`

### hidePopup

    public void hidePopup()

  Causes the combo box to close its popup window.

  See Also:
    `setPopupVisible(boolean)`

### setPopupVisible

    public void setPopupVisible(boolean v)

  Sets the visibility of the popup.

### isPopupVisible

    public boolean isPopupVisible()

  Determines the visibility of the popup.

  Returns:
    true if the popup is visible, otherwise returns false

### addItemListener

    public void addItemListener(ItemListener aListener)

  Adds an `ItemListener`.

  `aListener` will receive one or two `ItemEvent`s when the selected item changes.

  Specified by:
    `addItemListener` in interface `ItemSelectable`
  Parameters:
    `aListener` - the `ItemListener` that is to be notified
  See Also:
    `setSelectedItem(java.lang.Object)`

### removeItemListener

    public void removeItemListener(ItemListener aListener)

  Removes an `ItemListener`.

  Specified by:
    `removeItemListener` in interface `ItemSelectable`
  Parameters:
    `aListener` - the `ItemListener` to remove
  See Also:
    `ItemEvent`

### getItemListeners

    public ItemListener[] getItemListeners()

  Returns an array of all the `ItemListener`s added to this JComboBox with addItemListener().

  Returns:
    all of the `ItemListener`s added or an empty array if no listeners have been added
  Since:
    1.4

### addActionListener

    public void addActionListener(ActionListener l)

  Adds an `ActionListener`.

  The `ActionListener` will receive an `ActionEvent` when a selection has been made. If the combo box is editable, then an `ActionEvent` will be fired when editing has stopped.

  Parameters:
    `l` - the `ActionListener` that is to be notified
  See Also:
    `setSelectedItem(java.lang.Object)`

### removeActionListener

    public void removeActionListener(ActionListener l)

  Removes an `ActionListener`.

  Parameters:
    `l` - the `ActionListener` to remove

### getActionListeners

    public ActionListener[] getActionListeners()

  Returns an array of all the `ActionListener`s added to this JComboBox with addActionListener().

  Returns:
    all of the `ActionListener`s added or an empty array if no listeners have been added
  Since:
    1.4

### addPopupMenuListener

    public void addPopupMenuListener(PopupMenuListener l)

  Adds a `PopupMenu` listener which will listen to notification messages from the popup portion of the combo box.

  For all standard look and feels shipped with Java 2, the popup list portion of combo box is implemented as a `JPopupMenu`. A custom look and feel may not implement it this way and will therefore not receive the notification.

  Parameters:
    `l` - the `PopupMenuListener` to add
  Since:
    1.4

### removePopupMenuListener

    public void removePopupMenuListener(PopupMenuListener l)

  Removes a `PopupMenuListener`.

  Parameters:
    `l` - the `PopupMenuListener` to remove
  Since:
    1.4
  See Also:
    `addPopupMenuListener(javax.swing.event.PopupMenuListener)`

### getPopupMenuListeners

    public PopupMenuListener[] getPopupMenuListeners()

  Returns an array of all the `PopupMenuListener`s added to this JComboBox with addPopupMenuListener().

  Returns:
    all of the `PopupMenuListener`s added or an empty array if no listeners have been added
  Since:
    1.4

### firePopupMenuWillBecomeVisible

    public void firePopupMenuWillBecomeVisible()

  Notifies `PopupMenuListener`s that the popup portion of the combo box will become visible.

  This method is public but should not be called by anything other than the UI delegate.

  Since:
    1.4
  See Also:
    `addPopupMenuListener(javax.swing.event.PopupMenuListener)`

### firePopupMenuWillBecomeInvisible

    public void firePopupMenuWillBecomeInvisible()

  Notifies `PopupMenuListener`s that the popup portion of the combo box has become invisible.

  This method is public but should not be called by anything other than the UI delegate.

  Since:
    1.4
  See Also:
    `addPopupMenuListener(javax.swing.event.PopupMenuListener)`

### firePopupMenuCanceled

    public void firePopupMenuCanceled()

  Notifies `PopupMenuListener`s that the popup portion of the combo box has been canceled.

  This method is public but should not be called by anything other than the UI delegate.

  Since:
    1.4
  See Also:
    `addPopupMenuListener(javax.swing.event.PopupMenuListener)`

### setActionCommand

    public void setActionCommand(String aCommand)

  Sets the action command that should be included in the event sent to action listeners.

  Parameters:
    `aCommand` - a string containing the "command" that is sent to action listeners; the same listener can then do different things depending on the command it receives

### getActionCommand

    public String getActionCommand()

  Returns the action command that is included in the event sent to action listeners.

  Returns:
    the string containing the "command" that is sent to action listeners.

### setAction

    public void setAction(Action a)

  Sets the `Action` for the `ActionEvent` source. The new `Action` replaces any previously set `Action` but does not affect `ActionListeners` independently added with `addActionListener`. If the `Action` is already a registered `ActionListener` for the `ActionEvent` source, it is not re-registered.

  A side-effect of setting the `Action` is that the `ActionEvent` source's properties are immedately set from the values in the `Action` (performed by the method `configurePropertiesFromAction`) and subsequently updated as the `Action`'s properties change (via a `PropertyChangeListener` created by the method `createActionPropertyChangeListener`.

  Parameters:
    `a` - the `Action` for the `JComboBox`, or `null`.
  Since:
    1.3
  See Also:
    `Action`, `getAction()`, `configurePropertiesFromAction(javax.swing.Action)`, `createActionPropertyChangeListener(javax.swing.Action)`

### getAction

    public Action getAction()

  Returns the currently set `Action` for this `ActionEvent` source, or `null` if no `Action` is set.

  Returns:
    the `Action` for this `ActionEvent` source; or `null`
  Since:
    1.3
  See Also:
    `Action`, `setAction(javax.swing.Action)`

### configurePropertiesFromAction

    protected void configurePropertiesFromAction(Action a)

  Factory method which sets the `ActionEvent` source's properties according to values from the `Action` instance. The properties which are set may differ for subclasses. By default, the properties which get set are `Enabled` and `ToolTipText`.

  Parameters:
    `a` - the `Action` from which to get the properties, or `null`
  Since:
    1.3
  See Also:
    `Action`, `setAction(javax.swing.Action)`

### createActionPropertyChangeListener

    protected PropertyChangeListener createActionPropertyChangeListener(Action a)

  Factory method which creates the `PropertyChangeListener` used to update the `ActionEvent` source as properties change on its `Action` instance. Subclasses may override this in order to provide their own `PropertyChangeListener` if the set of properties which should be kept up to date differs from the default properties (Text, Icon, Enabled, ToolTipText). Note that `PropertyChangeListeners` should avoid holding strong references to the `ActionEvent` source, as this may hinder garbage collection of the `ActionEvent` source and all components in its containment hierarchy.

  Since:
    1.3
  See Also:
    `Action`, `setAction(javax.swing.Action)`

### fireItemStateChanged

    protected void fireItemStateChanged(ItemEvent e)

  Notifies all listeners that have registered interest for notification on this event type.

  Parameters:
    `e` - the event of interest
  See Also:
    `EventListenerList`

### fireActionEvent

    protected void fireActionEvent()

  Notifies all listeners that have registered interest for notification on this event type.

  See Also:
    `EventListenerList`

### selectedItemChanged

    protected void selectedItemChanged()

  This protected method is implementation specific. Do not access directly or override.

### getSelectedObjects

    public Object[] getSelectedObjects()

  Returns an array containing the selected item. This method is implemented for compatibility with `ItemSelectable`.

  Specified by:
    `getSelectedObjects` in interface `ItemSelectable`
  Returns:
    an array of `Objects` containing one element -- the selected item

### actionPerformed

    public void actionPerformed(ActionEvent e)

  This method is public as an implementation side effect. do not call or override.

  Specified by:
    `actionPerformed` in interface `ActionListener`

### contentsChanged

    public void contentsChanged(ListDataEvent e)

  This method is public as an implementation side effect. do not call or override.

  Specified by:
    `contentsChanged` in interface `ListDataListener`
  Parameters:
    `e` - a `ListDataEvent` encapsulating the event information

### intervalAdded

    public void intervalAdded(ListDataEvent e)

  This method is public as an implementation side effect. do not call or override.

  Specified by:
    `intervalAdded` in interface `ListDataListener`
  Parameters:
    `e` - a `ListDataEvent` encapsulating the event information

### intervalRemoved

    public void intervalRemoved(ListDataEvent e)

  This method is public as an implementation side effect. do not call or override.

  Specified by:
    `intervalRemoved` in interface `ListDataListener`
  Parameters:
    `e` - a `ListDataEvent` encapsulating the event information

### selectWithKeyChar

    public boolean selectWithKeyChar(char keyChar)

  Selects the list item that corresponds to the specified keyboard character and returns true, if there is an item corresponding to that character. Otherwise, returns false.

  Parameters:
    `keyChar` - a char, typically this is a keyboard key typed by the user

### setEnabled

    public void setEnabled(boolean b)

  Enables the combo box so that items can be selected. When the combo box is disabled, items cannot be selected and values cannot be typed into its field (if it is editable).

  Overrides:
    `setEnabled` in class `JComponent`
  Parameters:
    `b` - a boolean value, where true enables the component and false disables it
  See Also:
    `Component.isEnabled()`, `Component.isLightweight()`

### configureEditor

    public void configureEditor(ComboBoxEditor anEditor,
                                Object anItem)

  Initializes the editor with the specified item.

  Parameters:
    `anEditor` - the `ComboBoxEditor` that displays the list item in the combo box field and allows it to be edited
    `anItem` - the object to display and edit in the field

### processKeyEvent

    public void processKeyEvent(KeyEvent e)

  Handles `KeyEvent`s, looking for the Tab key. If the Tab key is found, the popup window is closed.

  Overrides:
    `processKeyEvent` in class `JComponent`
  Parameters:
    `e` - the `KeyEvent` containing the keyboard key that was pressed
  See Also:
    `KeyEvent`, `KeyListener`, `Component.addKeyListener(java.awt.event.KeyListener)`, `Component.enableEvents(long)`, `Component.isShowing()`

### setKeySelectionManager

    public void setKeySelectionManager(JComboBox.KeySelectionManager aManager)

  Sets the object that translates a keyboard character into a list selection. Typically, the first selection with a matching first character becomes the selected item.

### getKeySelectionManager

    public JComboBox.KeySelectionManager getKeySelectionManager()

  Returns the list's key-selection manager.

  Returns:
    the `KeySelectionManager` currently in use

### getItemCount

    public int getItemCount()

  Returns the number of items in the list.

  Returns:
    an integer equal to the number of items in the list

### getItemAt

    public Object getItemAt(int index)

  Returns the list item at the specified index. If `index` is out of range (less than zero or greater than or equal to size) it will return `null`.

  Parameters:
    `index` - an integer indicating the list position, where the first item starts at zero
  Returns:
    the `Object` at that list position; or `null` if out of range

### createDefaultKeySelectionManager

    protected JComboBox.KeySelectionManager createDefaultKeySelectionManager()

  Returns an instance of the default key-selection manager.

  Returns:
    the `KeySelectionManager` currently used by the list
  See Also:
    `setKeySelectionManager(javax.swing.JComboBox.KeySelectionManager)`

### paramString

    protected String paramString()

  Returns a string representation of this `JComboBox`. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be `null`.

  Overrides:
    `paramString` in class `JComponent`
  Returns:
    a string representation of this `JComboBox`

### getAccessibleContext

    public AccessibleContext getAccessibleContext()

  Gets the AccessibleContext associated with this JComboBox. For combo boxes, the AccessibleContext takes the form of an AccessibleJComboBox. A new AccessibleJComboBox instance is created if necessary.

  Specified by:
    `getAccessibleContext` in interface `Accessible`
  Overrides:
    `getAccessibleContext` in class `JComponent`
  Returns:
    an AccessibleJComboBox that serves as the AccessibleContext of this JComboBox

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