- java.lang.Object
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- java.awt.Component
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- java.awt.Checkbox
 
 
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- All Implemented Interfaces:
- ImageObserver,- ItemSelectable,- MenuContainer,- Serializable,- Accessible
 
 public class Checkbox extends Component implements ItemSelectable, Accessible A check box is a graphical component that can be in either an "on" (true) or "off" (false) state. Clicking on a check box changes its state from "on" to "off," or from "off" to "on."The following code example creates a set of check boxes in a grid layout: setLayout(new GridLayout(3, 1)); add(new Checkbox("one", null, true)); add(new Checkbox("two")); add(new Checkbox("three"));
 This image depicts the check boxes and grid layout created by this code example:   The button labeled oneis in the "on" state, and the other two are in the "off" state. In this example, which uses theGridLayoutclass, the states of the three check boxes are set independently.Alternatively, several check boxes can be grouped together under the control of a single object, using the CheckboxGroupclass. In a check box group, at most one button can be in the "on" state at any given time. Clicking on a check box to turn it on forces any other check box in the same group that is on into the "off" state.- Since:
- 1.0
- See Also:
- GridLayout,- CheckboxGroup, Serialized Form
 
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Nested Class SummaryNested Classes Modifier and Type Class Description protected classCheckbox.AccessibleAWTCheckboxThis class implements accessibility support for theCheckboxclass.- 
Nested classes/interfaces declared in class java.awt.ComponentComponent.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy
 
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Field Summary- 
Fields declared in class java.awt.ComponentaccessibleContext, BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT
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Fields declared in interface java.awt.image.ImageObserverABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH
 
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Constructor SummaryConstructors Constructor Description Checkbox()Creates a check box with an empty string for its label.Checkbox(String label)Creates a check box with the specified label.Checkbox(String label, boolean state)Creates a check box with the specified label and sets the specified state.Checkbox(String label, boolean state, CheckboxGroup group)Constructs a Checkbox with the specified label, set to the specified state, and in the specified check box group.Checkbox(String label, CheckboxGroup group, boolean state)Creates a check box with the specified label, in the specified check box group, and set to the specified state.
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Method SummaryAll Methods Instance Methods Concrete Methods Modifier and Type Method Description voidaddItemListener(ItemListener l)Adds the specified item listener to receive item events from this check box.voidaddNotify()Creates the peer of the Checkbox.AccessibleContextgetAccessibleContext()Gets the AccessibleContext associated with this Checkbox.CheckboxGroupgetCheckboxGroup()Determines this check box's group.ItemListener[]getItemListeners()Returns an array of all the item listeners registered on this checkbox.StringgetLabel()Gets the label of this check box.<T extends EventListener>
 T[]getListeners(Class<T> listenerType)Returns an array of all the objects currently registered asFooListeners upon thisCheckbox.Object[]getSelectedObjects()Returns an array (length 1) containing the checkbox label or null if the checkbox is not selected.booleangetState()Determines whether this check box is in the "on" or "off" state.protected StringparamString()Returns a string representing the state of thisCheckbox.protected voidprocessEvent(AWTEvent e)Processes events on this check box.protected voidprocessItemEvent(ItemEvent e)Processes item events occurring on this check box by dispatching them to any registeredItemListenerobjects.voidremoveItemListener(ItemListener l)Removes the specified item listener so that the item listener no longer receives item events from this check box.voidsetCheckboxGroup(CheckboxGroup g)Sets this check box's group to the specified check box group.voidsetLabel(String label)Sets this check box's label to be the string argument.voidsetState(boolean state)Sets the state of this check box to the specified state.- 
Methods declared in class java.awt.Componentaction, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, createVolatileImage, createVolatileImage, deliverEvent, disable, disableEvents, dispatchEvent, doLayout, enable, enable, enableEvents, enableInputMethods, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getAlignmentX, getAlignmentY, getBackground, getBaseline, getBaselineResizeBehavior, getBounds, getBounds, getColorModel, getComponentAt, getComponentAt, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeys, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocale, getLocation, getLocation, getLocationOnScreen, getMaximumSize, getMinimumSize, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPreferredSize, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, invalidate, isBackgroundSet, isCursorSet, isDisplayable, isDoubleBuffered, isEnabled, isFocusable, isFocusCycleRoot, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isPreferredSizeSet, isShowing, isValid, isVisible, keyDown, keyUp, layout, list, list, list, list, list, locate, location, lostFocus, minimumSize, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paint, paintAll, postEvent, preferredSize, prepareImage, prepareImage, print, printAll, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, requestFocus, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, requestFocusInWindow, reshape, resize, resize, revalidate, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFocusable, setFocusTraversalKeys, setFocusTraversalKeysEnabled, setFont, setForeground, setIgnoreRepaint, setLocale, setLocation, setLocation, setMaximumSize, setMinimumSize, setMixingCutoutShape, setName, setPreferredSize, setSize, setSize, setVisible, show, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle, update, validate
 
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Constructor Detail- 
Checkboxpublic Checkbox() throws HeadlessExceptionCreates a check box with an empty string for its label. The state of this check box is set to "off," and it is not part of any check box group.- Throws:
- HeadlessException- if GraphicsEnvironment.isHeadless() returns true
- See Also:
- GraphicsEnvironment.isHeadless()
 
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Checkboxpublic Checkbox(String label) throws HeadlessException Creates a check box with the specified label. The state of this check box is set to "off," and it is not part of any check box group.- Parameters:
- label- a string label for this check box, or- nullfor no label.
- Throws:
- HeadlessException- if- GraphicsEnvironment.isHeadlessreturns- true
- See Also:
- GraphicsEnvironment.isHeadless()
 
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Checkboxpublic Checkbox(String label, boolean state) throws HeadlessException Creates a check box with the specified label and sets the specified state. This check box is not part of any check box group.- Parameters:
- label- a string label for this check box, or- nullfor no label
- state- the initial state of this check box
- Throws:
- HeadlessException- if- GraphicsEnvironment.isHeadlessreturns- true
- See Also:
- GraphicsEnvironment.isHeadless()
 
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Checkboxpublic Checkbox(String label, boolean state, CheckboxGroup group) throws HeadlessException Constructs a Checkbox with the specified label, set to the specified state, and in the specified check box group.- Parameters:
- label- a string label for this check box, or- nullfor no label.
- state- the initial state of this check box.
- group- a check box group for this check box, or- nullfor no group.
- Throws:
- HeadlessException- if- GraphicsEnvironment.isHeadlessreturns- true
- Since:
- 1.1
- See Also:
- GraphicsEnvironment.isHeadless()
 
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Checkboxpublic Checkbox(String label, CheckboxGroup group, boolean state) throws HeadlessException Creates a check box with the specified label, in the specified check box group, and set to the specified state.- Parameters:
- label- a string label for this check box, or- nullfor no label.
- group- a check box group for this check box, or- nullfor no group.
- state- the initial state of this check box.
- Throws:
- HeadlessException- if- GraphicsEnvironment.isHeadlessreturns- true
- Since:
- 1.1
- See Also:
- GraphicsEnvironment.isHeadless()
 
 
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Method Detail- 
addNotifypublic void addNotify() Creates the peer of the Checkbox. The peer allows you to change the look of the Checkbox without changing its functionality.- Overrides:
- addNotifyin class- Component
- See Also:
- Component.getToolkit()
 
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getLabelpublic String getLabel() Gets the label of this check box.- Returns:
- the label of this check box, or nullif this check box has no label.
- See Also:
- setLabel(String)
 
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setLabelpublic void setLabel(String label) Sets this check box's label to be the string argument.- Parameters:
- label- a string to set as the new label, or- nullfor no label.
- See Also:
- getLabel()
 
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getStatepublic boolean getState() Determines whether this check box is in the "on" or "off" state. The boolean valuetrueindicates the "on" state, andfalseindicates the "off" state.- Returns:
- the state of this check box, as a boolean value
- See Also:
- setState(boolean)
 
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setStatepublic void setState(boolean state) Sets the state of this check box to the specified state. The boolean valuetrueindicates the "on" state, andfalseindicates the "off" state.Note that this method should be primarily used to initialize the state of the checkbox. Programmatically setting the state of the checkbox will not trigger an ItemEvent. The only way to trigger anItemEventis by user interaction.- Parameters:
- state- the boolean state of the check box
- See Also:
- getState()
 
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getSelectedObjectspublic Object[] getSelectedObjects() Returns an array (length 1) containing the checkbox label or null if the checkbox is not selected.- Specified by:
- getSelectedObjectsin interface- ItemSelectable
- Returns:
- the list of selected objects, or null
- See Also:
- ItemSelectable
 
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getCheckboxGrouppublic CheckboxGroup getCheckboxGroup() Determines this check box's group.- Returns:
- this check box's group, or nullif the check box is not part of a check box group.
- See Also:
- setCheckboxGroup(CheckboxGroup)
 
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setCheckboxGrouppublic void setCheckboxGroup(CheckboxGroup g) Sets this check box's group to the specified check box group. If this check box is already in a different check box group, it is first taken out of that group.If the state of this check box is trueand the new group already has a check box selected, this check box's state is changed tofalse. If the state of this check box istrueand the new group has no check box selected, this check box becomes the selected checkbox for the new group and its state istrue.- Parameters:
- g- the new check box group, or- nullto remove this check box from any check box group
- See Also:
- getCheckboxGroup()
 
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addItemListenerpublic void addItemListener(ItemListener l) Adds the specified item listener to receive item events from this check box. Item events are sent to listeners in response to user input, but not in response to calls to setState(). If l is null, no exception is thrown and no action is performed.Refer to AWT Threading Issues for details on AWT's threading model. - Specified by:
- addItemListenerin interface- ItemSelectable
- Parameters:
- l- the item listener
- Since:
- 1.1
- See Also:
- removeItemListener(java.awt.event.ItemListener),- getItemListeners(),- setState(boolean),- ItemEvent,- ItemListener
 
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removeItemListenerpublic void removeItemListener(ItemListener l) Removes the specified item listener so that the item listener no longer receives item events from this check box. If l is null, no exception is thrown and no action is performed.Refer to AWT Threading Issues for details on AWT's threading model. - Specified by:
- removeItemListenerin interface- ItemSelectable
- Parameters:
- l- the item listener
- Since:
- 1.1
- See Also:
- addItemListener(java.awt.event.ItemListener),- getItemListeners(),- ItemEvent,- ItemListener
 
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getItemListenerspublic ItemListener[] getItemListeners() Returns an array of all the item listeners registered on this checkbox.- Returns:
- all of this checkbox's ItemListeners or an empty array if no item listeners are currently registered
- Since:
- 1.4
- See Also:
- addItemListener(java.awt.event.ItemListener),- removeItemListener(java.awt.event.ItemListener),- ItemEvent,- ItemListener
 
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getListenerspublic <T extends EventListener> T[] getListeners(Class<T> listenerType) Returns an array of all the objects currently registered asFooListeners upon thisCheckbox.FooListeners are registered using theaddFooListenermethod.You can specify the listenerTypeargument with a class literal, such asFooListener.class. For example, you can query aCheckbox cfor its item listeners with the following code:ItemListener[] ils = (ItemListener[])(c.getListeners(ItemListener.class)); If no such listeners exist, this method returns an empty array.- Overrides:
- getListenersin class- Component
- Type Parameters:
- T- the type of the listeners
- Parameters:
- listenerType- the type of listeners requested; this parameter should specify an interface that descends from- java.util.EventListener
- Returns:
- an array of all objects registered as
          FooListeners on this checkbox, or an empty array if no such listeners have been added
- Throws:
- ClassCastException- if- listenerTypedoesn't specify a class or interface that implements- java.util.EventListener
- Since:
- 1.3
- See Also:
- getItemListeners()
 
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processEventprotected void processEvent(AWTEvent e) Processes events on this check box. If the event is an instance ofItemEvent, this method invokes theprocessItemEventmethod. Otherwise, it calls its superclass'sprocessEventmethod.Note that if the event parameter is nullthe behavior is unspecified and may result in an exception.- Overrides:
- processEventin class- Component
- Parameters:
- e- the event
- Since:
- 1.1
- See Also:
- ItemEvent,- processItemEvent(java.awt.event.ItemEvent)
 
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processItemEventprotected void processItemEvent(ItemEvent e) Processes item events occurring on this check box by dispatching them to any registeredItemListenerobjects.This method is not called unless item events are enabled for this component. Item events are enabled when one of the following occurs: - An ItemListenerobject is registered viaaddItemListener.
- Item events are enabled via enableEvents.
 Note that if the event parameter is nullthe behavior is unspecified and may result in an exception.- Parameters:
- e- the item event
- Since:
- 1.1
- See Also:
- ItemEvent,- ItemListener,- addItemListener(java.awt.event.ItemListener),- Component.enableEvents(long)
 
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paramStringprotected String paramString() Returns a string representing the state of thisCheckbox. 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 benull.- Overrides:
- paramStringin class- Component
- Returns:
- the parameter string of this check box
 
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getAccessibleContextpublic AccessibleContext getAccessibleContext() Gets the AccessibleContext associated with this Checkbox. For checkboxes, the AccessibleContext takes the form of an AccessibleAWTCheckbox. A new AccessibleAWTCheckbox is created if necessary.- Specified by:
- getAccessibleContextin interface- Accessible
- Overrides:
- getAccessibleContextin class- Component
- Returns:
- an AccessibleAWTCheckbox that serves as the AccessibleContext of this Checkbox
- Since:
- 1.3
 
 
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