Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.
Returns: the component argument
Parameters:
- comp - the component to be added
Throws:
- NullPointerException - if {@code comp} is {@code null}
See Also: Container.addImpl(java.awt.Component, java.lang.Object, int), Container.validate(), JComponent.revalidate(),

Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.
Returns: the component comp
Parameters:
- comp - the component to be added
- index - the position at which to insert the component, or -1 to append the component to the end
Throws:
- NullPointerException - if {@code comp} is {@code null}
- IllegalArgumentException - if {@code index} is invalid (see {@link #addImpl} for details)
See Also: Container.addImpl(java.awt.Component, java.lang.Object, int), Container.remove(int), Container.validate(), JComponent.revalidate(),

Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.
Parameters:
- comp - the component to be added
- constraints - an object expressing layout contraints for this component
Throws:
- NullPointerException - if {@code comp} is {@code null}
Since: JDK1.1
See Also: Container.addImpl(java.awt.Component, java.lang.Object, int), Container.validate(), JComponent.revalidate(), LayoutManager,

Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.
Parameters:
- comp - the component to be added
- constraints - an object expressing layout contraints for this
- index - the position in the container's list at which to insert the component; -1 means insert at the end component
Throws:
- NullPointerException - if {@code comp} is {@code null}
- IllegalArgumentException - if {@code index} is invalid (see {@link #addImpl} for details)
See Also: Container.addImpl(java.awt.Component, java.lang.Object, int), Container.validate(), JComponent.revalidate(), Container.remove(int), LayoutManager,

This method is obsolete as of 1.1. Please use the method add(Component, Object) instead.
Throws:
- NullPointerException - if {@code comp} is {@code null}
See Also: Container.add(Component, Object),

Refer to AWT Threading Issues for details on AWT's threading model.
Parameters:
- l - the component listener
Since: JDK1.1
See Also: ComponentEvent, ComponentListener, Component.removeComponentListener(java.awt.event.ComponentListener), Component.getComponentListeners(),

Refer to AWT Threading Issues for details on AWT's threading model.
Parameters:
- l - the container listener
See Also: Container.removeContainerListener(java.awt.event.ContainerListener), Container.getContainerListeners(),

Refer to AWT Threading Issues for details on AWT's threading model.
Parameters:
- l - the focus listener
Since: JDK1.1
See Also: FocusEvent, FocusListener, Component.removeFocusListener(java.awt.event.FocusListener), Component.getFocusListeners(),

Refer to AWT Threading Issues for details on AWT's threading model.
Parameters:
- l - the hierarchy bounds listener
Since: 1.3
See Also: HierarchyEvent, HierarchyBoundsListener, Component.removeHierarchyBoundsListener(java.awt.event.HierarchyBoundsListener), Component.getHierarchyBoundsListeners(),

Refer to AWT Threading Issues for details on AWT's threading model.
Parameters:
- l - the hierarchy listener
Since: 1.3
See Also: HierarchyEvent, HierarchyListener, Component.removeHierarchyListener(java.awt.event.HierarchyListener), Component.getHierarchyListeners(),

The constraints are defined by the particular layout manager being used. For example, the BorderLayout class defines five constraints: BorderLayout.NORTH, BorderLayout.SOUTH, BorderLayout.EAST, BorderLayout.WEST, and BorderLayout.CENTER.

The GridBagLayout class requires a GridBagConstraints object. Failure to pass the correct type of constraints object results in an IllegalArgumentException.

If the current layout manager implements LayoutManager2, then LayoutManager2.addLayoutComponent(Component,Object) is invoked on it. If the current layout manager does not implement LayoutManager2, and constraints is a String, then LayoutManager.addLayoutComponent(String,Component) is invoked on it.

If the component is not an ancestor of this container and has a non-null parent, it is removed from its current parent before it is added to this container.

This is the method to override if a program needs to track every add request to a container as all other add methods defer to this one. An overriding method should usually include a call to the superclass's version of the method:

super.addImpl(comp, constraints, index)

Parameters:
- comp - the component to be added
- constraints - an object expressing layout constraints for this component
- index - the position in the container's list at which to insert the component, where -1 means append to the end
Throws:
- IllegalArgumentException - if {@code index} is invalid; if {@code comp} is a child of this container, the valid range is {@code [-1, getComponentCount()-1]}; if component is not a child of this container, the valid range is {@code [-1, getComponentCount()]}
- IllegalArgumentException - if {@code comp} is an ancestor of this container
- IllegalArgumentException - if adding a window to a container
- NullPointerException - if {@code comp} is {@code null}
Since: JDK1.1
See Also: Container.add(Component), Container.add(Component, int), Container.add(Component, java.lang.Object), LayoutManager, LayoutManager2,

Refer to AWT Threading Issues for details on AWT's threading model.
Parameters:
- l - the input method listener
Since: 1.2
See Also: InputMethodEvent, InputMethodListener, Component.removeInputMethodListener(java.awt.event.InputMethodListener), Component.getInputMethodListeners(), Component.getInputMethodRequests(),

Refer to AWT Threading Issues for details on AWT's threading model.
Parameters:
- l - the key listener.
Since: JDK1.1
See Also: KeyEvent, KeyListener, Component.removeKeyListener(java.awt.event.KeyListener), Component.getKeyListeners(),

Refer to AWT Threading Issues for details on AWT's threading model.
Parameters:
- l - the mouse listener
Since: JDK1.1
See Also: MouseEvent, MouseListener, Component.removeMouseListener(java.awt.event.MouseListener), Component.getMouseListeners(),

Refer to AWT Threading Issues for details on AWT's threading model.
Parameters:
- l - the mouse motion listener
Since: JDK1.1
See Also: MouseEvent, MouseMotionListener, Component.removeMouseMotionListener(java.awt.event.MouseMotionListener), Component.getMouseMotionListeners(),

For information on how mouse wheel events are dispatched, see the class description for MouseWheelEvent.

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.
Parameters:
- l - the mouse wheel listener
Since: 1.4
See Also: MouseWheelEvent, MouseWheelListener, Component.removeMouseWheelListener(java.awt.event.MouseWheelListener), Component.getMouseWheelListeners(),

• this Container's font ("font")
• this Container's background color ("background")
• this Container's foreground color ("foreground")
• this Container's focusability ("focusable")
• this Container's focus traversal keys enabled state ("focusTraversalKeysEnabled")
• this Container's Set of FORWARD_TRAVERSAL_KEYS ("forwardFocusTraversalKeys")
• this Container's Set of BACKWARD_TRAVERSAL_KEYS ("backwardFocusTraversalKeys")
• this Container's Set of UP_CYCLE_TRAVERSAL_KEYS ("upCycleFocusTraversalKeys")
• this Container's Set of DOWN_CYCLE_TRAVERSAL_KEYS ("downCycleFocusTraversalKeys")
• this Container's focus traversal policy ("focusTraversalPolicy")
• this Container's focus-cycle-root state ("focusCycleRoot")

If listener is null, no exception is thrown and no action is performed.
Parameters:
- listener - the PropertyChangeListener to be added
See Also: Component.removePropertyChangeListener(java.beans.PropertyChangeListener), Container.addPropertyChangeListener(java.lang.String,java.beans.PropertyChangeListener),

• this Container's font ("font")
• this Container's background color ("background")
• this Container's foreground color ("foreground")
• this Container's focusability ("focusable")
• this Container's focus traversal keys enabled state ("focusTraversalKeysEnabled")
• this Container's Set of FORWARD_TRAVERSAL_KEYS ("forwardFocusTraversalKeys")
• this Container's Set of BACKWARD_TRAVERSAL_KEYS ("backwardFocusTraversalKeys")
• this Container's Set of UP_CYCLE_TRAVERSAL_KEYS ("upCycleFocusTraversalKeys")
• this Container's Set of DOWN_CYCLE_TRAVERSAL_KEYS ("downCycleFocusTraversalKeys")
• this Container's focus traversal policy ("focusTraversalPolicy")
• this Container's focus-cycle-root state ("focusCycleRoot")
• this Container's focus-traversal-policy-provider state("focusTraversalPolicyProvider")
• this Container's focus-traversal-policy-provider state("focusTraversalPolicyProvider")

If listener is null, no exception is thrown and no action is performed.
Parameters:
- propertyName - one of the property names listed above
- listener - the PropertyChangeListener to be added
See Also: Container.addPropertyChangeListener(java.beans.PropertyChangeListener), Component.removePropertyChangeListener(java.beans.PropertyChangeListener),

This method does not cause the image to begin loading. An application must use the prepareImage method to force the loading of an image.

Information on the flags returned by this method can be found with the discussion of the ImageObserver interface.
Returns: the bitwise inclusive OR of ImageObserver flags indicating what information about the image is currently available
Parameters:
- image - the Image object whose status is being checked
- observer - the ImageObserver object to be notified as the image is being prepared
Since: JDK1.0
See Also: Component.prepareImage(Image, int, int, java.awt.image.ImageObserver), Toolkit.checkImage(Image, int, int, java.awt.image.ImageObserver), ImageObserver,

This method does not cause the image to begin loading. An application must use the prepareImage method to force the loading of an image.

The checkImage method of Component calls its peer's checkImage method to calculate the flags. If this component does not yet have a peer, the component's toolkit's checkImage method is called instead.

Information on the flags returned by this method can be found with the discussion of the ImageObserver interface.
Returns: the bitwise inclusive OR of ImageObserver flags indicating what information about the image is currently available
Parameters:
- image - the Image object whose status is being checked
- width - the width of the scaled version whose status is to be checked
- height - the height of the scaled version whose status is to be checked
- observer - the ImageObserver object to be notified as the image is being prepared
Since: JDK1.0
See Also: Component.prepareImage(Image, int, int, java.awt.image.ImageObserver), Toolkit.checkImage(Image, int, int, java.awt.image.ImageObserver), ImageObserver,

This implementation of coalesceEvents coalesces two event types: mouse move (and drag) events, and paint (and update) events. For mouse move events the last event is always returned, causing intermediate moves to be discarded. For paint events, the new event is coalesced into a complex RepaintArea in the peer. The new AWTEvent is always returned.
Returns: a coalesced event, or null indicating that no coalescing was done
Parameters:
- existingEvent - the event already on the EventQueue
- newEvent - the event being posted to the EventQueue

Event types are automatically enabled when a listener for that event type is added to the component.

This method only needs to be invoked by subclasses of Component which desire to have the specified event types delivered to processEvent regardless of whether or not a listener is registered.
Parameters:
- eventsToEnable - the event mask defining the event types
Since: JDK1.1
See Also: Component.processEvent(java.awt.AWTEvent), Component.disableEvents(long), AWTEvent,

The findComponentAt method is different from getComponentAt in that getComponentAt only searches the Container's immediate children; if the containing component is a Container, findComponentAt will search that child to find a nested component.
Returns: null if the component does not contain the position. If there is no child component at the requested point and the point is within the bounds of the container the container itself is returned.
Parameters:
- x - the x coordinate
- y - the y coordinate
Since: 1.2
See Also: Component.contains(int, int), Container.getComponentAt(int, int),

The findComponentAt method is different from getComponentAt in that getComponentAt only searches the Container's immediate children; if the containing component is a Container, findComponentAt will search that child to find a nested component.
Returns: null if the component does not contain the position. If there is no child component at the requested point and the point is within the bounds of the container the container itself is returned.
Parameters:
- p - the point.
Since: 1.2
See Also: Component.contains(int, int), Container.getComponentAt(int, int),

This method calls into the ComponentUI method of the same name. If this component does not have a ComponentUI -1 will be returned. If a value >= 0 is returned, then the component has a valid baseline for any size >= the minimum size and getBaselineResizeBehavior can be used to determine how the baseline changes with size.
Throws:
- IllegalArgumentException - {@inheritDoc}
Since: 1.6
See Also: JComponent.getBaselineResizeBehavior(), FontMetrics,

This method calls into the ComponentUI method of the same name. If this component does not have a ComponentUI BaselineResizeBehavior.OTHER will be returned. Subclasses should never return null; if the baseline can not be calculated return BaselineResizeBehavior.OTHER. Callers should first ask for the baseline using getBaseline and if a value >= 0 is returned use this method. It is acceptable for this method to return a value other than BaselineResizeBehavior.OTHER even if getBaseline returns a value less than 0.
Since: 1.6
See Also: JComponent.getBaseline(int, int),

For Java 2 platform v1.3, a KeyStroke can be associated with more than one condition. For example, 'a' could be bound for the two conditions WHEN_FOCUSED and WHEN_IN_FOCUSED_WINDOW condition.
Returns: the action-keystroke condition

• DebugGraphics.LOG_OPTION - causes a text message to be printed.
• DebugGraphics.FLASH_OPTION - causes the drawing to flash several times.
• DebugGraphics.BUFFERED_OPTION - creates an ExternalWindow that displays the operations performed on the View's offscreen buffer.
• DebugGraphics.NONE_OPTION disables debugging.
• A value of 0 causes no changes to the debugging options.

If a Set of traversal keys has not been explicitly defined for this Container, then this Container's parent's Set is returned. If no Set has been explicitly defined for any of this Container's ancestors, then the current KeyboardFocusManager's default Set is returned.
Returns: the Set of AWTKeyStrokes for the specified operation. The Set will be unmodifiable, and may be empty. null will never be returned.
Parameters:
- id - one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS
Throws:
- IllegalArgumentException - if id is not one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS
Since: 1.4
See Also: Container.setFocusTraversalKeys(int, java.util.Set), KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS,

• JComponent.FOCUS_INPUTMAP_CREATED
• JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT
• JComponent.WHEN_IN_FOCUSED_WINDOW

You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a JComponent c for its mouse listeners with the following code:

MouseListener[] mls = (MouseListener[])(c.getListeners(MouseListener.class));

Due to the asynchronous nature of native event handling, this method can return outdated values (for instance, after several calls of setLocation() in rapid succession). For this reason, the recommended method of obtaining a component's position is within java.awt.event.ComponentListener.componentMoved(), which is called after the operating system has finished moving the component.

For Containers it returns a non-null value if the mouse is above the Container itself or above any of its descendants. Use Container.getMousePosition(boolean) if you need to exclude children.

Sometimes the exact mouse coordinates are not important, and the only thing that matters is whether a specific Component is under the mouse pointer. If the return value of this method is null, mouse pointer is not directly above the Component.
Returns: mouse coordinates relative to this Component, or null
Throws:
- HeadlessException - if GraphicsEnvironment.isHeadless() returns true
Since: 1.5
See Also: Component.isShowing(), Container.getMousePosition(boolean),

Returns the Component set by a prior call to setNextFocusableComponent(Component) on this JComponent.
Returns: the Component that will follow this JComponent in the focus traversal cycle, or null if none has been explicitly specified
See Also: JComponent.setNextFocusableComponent(java.awt.Component),

This method is intended for use by focus implementations. Client code should not use this method; instead, it should use requestFocusInWindow().
See Also: JComponent.requestFocusInWindow(),

The imageUpdate method of Component incrementally draws an image on the component as more of the bits of the image are available.

If the system property awt.image.incrementaldraw is missing or has the value true, the image is incrementally drawn. If the system property has any other value, then the image is not drawn until it has been completely loaded.

Also, if incremental drawing is in effect, the value of the system property awt.image.redrawrate is interpreted as an integer to give the maximum redraw rate, in milliseconds. If the system property is missing or cannot be interpreted as an integer, the redraw rate is once every 100ms.

The interpretation of the x, y, width, and height arguments depends on the value of the infoflags argument.
Returns: false if the infoflags indicate that the image is completely loaded; true otherwise.
Parameters:
- img - the image being observed
- infoflags - see imageUpdate for more information
- x - the x coordinate
- y - the y coordinate
- w - the width
- h - the height
Since: JDK1.0
See Also: ImageObserver, Graphics.drawImage(Image, int, int, Color, java.awt.image.ImageObserver), Graphics.drawImage(Image, int, int, java.awt.image.ImageObserver), Graphics.drawImage(Image, int, int, int, int, Color, java.awt.image.ImageObserver), Graphics.drawImage(Image, int, int, int, int, java.awt.image.ImageObserver), ImageObserver.imageUpdate(java.awt.Image, int, int, int, int, int),

If the LayoutManager installed on this container is an instance of LayoutManager2, then LayoutManager2.invalidateLayout(Container) is invoked on it supplying this Container as the argument.
See Also: Container.validate(), Container.layout(), LayoutManager, LayoutManager2.invalidateLayout(Container),

A component is made displayable either when it is added to a displayable containment hierarchy or when its containment hierarchy is made displayable. A containment hierarchy is made displayable when its ancestor window is either packed or made visible.

A component is made undisplayable either when it is removed from a displayable containment hierarchy or when its containment hierarchy is made undisplayable. A containment hierarchy is made undisplayable when its ancestor window is disposed.
Returns: true if the component is displayable, false otherwise
Since: 1.2
See Also: Container.add(Component), Window.pack(), Window.show(), Container.remove(Component), Window.dispose(),

This method will always return false if this component is not displayable because it is impossible to determine the weight of an undisplayable component.
Returns: true if this component has a lightweight peer; false if it has a native peer or no peer
Since: 1.2
See Also: Component.isDisplayable(),

Changes this JComponent's focus traversal keys to CTRL+TAB and CTRL+SHIFT+TAB. Also prevents SortingFocusTraversalPolicy from considering descendants of this JComponent when computing a focus traversal cycle.
See Also: Component.setFocusTraversalKeys(int, java.util.Set), SortingFocusTraversalPolicy,

An opaque component paints every pixel within its rectangular bounds. A non-opaque component paints only a subset of its pixels or none at all, allowing the pixels underneath it to "show through". Therefore, a component that does not fully paint its pixels provides a degree of transparency.

Subclasses that guarantee to always completely paint their contents should override this method and return true.
Returns: true if this component is completely opaque
See Also: JComponent.setOpaque(boolean),

You can detect changes in the value of this property by listening for property change events on this component with name "paintingForPrint".

Note: This method provides complimentary functionality to that provided by other high level Swing printing APIs. However, it deals strictly with painting and should not be confused as providing information on higher level print processes. For example, a JTable.print() operation doesn't necessarily result in a continuous rendering of the full component, and the return value of this method can change multiple times during that operation. It is even possible for the component to be painted to the screen while the printing process is ongoing. In such a case, the return value of this method is true when, and only when, the table is being painted as part of the printing process.
Returns: true if the current painting operation on this component is part of a print operation
Since: 1.6
See Also: JComponent.print(java.awt.Graphics),

Please see How to Use the Focus Subsystem, a section in The Java Tutorial, for more information.
Returns: true if this component should get focus, otherwise returns false
See Also: JComponent.setRequestFocusEnabled(boolean), Focus Specification, Component.isFocusable(),

Note: sometimes there is no way to detect whether the Component is actually visible to the user. This can happen when:

• the component has been added to a visible ScrollPane but the Component is not currently in the scroll pane's view port.
• the Component is obscured by another Component or Container.

The immediate children of the container are printed with an indentation of indent+1. The children of those children are printed at indent+2 and so on.
Parameters:
- out - a print stream
- indent - the number of spaces to indent
Since: JDK1.0
See Also: Component.list(java.io.PrintStream, int),