# Class JPanel

java.lang.Object
java.awt.Component
java.awt.Container
javax.swing.JComponent
javax.swing.JPanel

All Implemented Interfaces:
  `ImageObserver, MenuContainer, Serializable, Accessible`

Direct Known Subclasses:
  `AbstractColorChooserPanel, JSpinner.DefaultEditor`

@JavaBean(defaultProperty="UI", description="A generic lightweight container.") public class JPanel extends JComponent implements Accessible
`JPanel` is a generic lightweight container. For examples and task-oriented documentation for JPanel, see How to Use Panels, a section in The Java Tutorial.

Warning: Swing is not thread safe. For more information see Swing's Threading Policy.

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 JavaBeans has been added to the `java.beans` package. Please see `XMLEncoder`.

Since:
  1.2

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `protected class`
  `JPanel.AccessibleJPanel`
  This class implements accessibility support for the `JPanel` class.

  ### Nested classes/interfaces declared in class JComponent

  `JComponent.AccessibleJComponent`

  ### Nested classes/interfaces declared in class Container

  `Container.AccessibleAWTContainer`

  ### Nested classes/interfaces declared in class Component

  `Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy`

- ## Field Summary

  ### Fields declared in class JComponent

  `listenerList, TOOL_TIP_TEXT_KEY, ui, UNDEFINED_CONDITION, WHEN_ANCESTOR_OF_FOCUSED_COMPONENT, WHEN_FOCUSED, WHEN_IN_FOCUSED_WINDOW`

  ### Fields declared in class Component

  `accessibleContext, BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT`

  ### Fields declared in interface ImageObserver

  `ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `JPanel()`
  Creates a new `JPanel` with a double buffer and a flow layout.
  `JPanel(boolean isDoubleBuffered)`
  Creates a new `JPanel` with `FlowLayout` and the specified buffering strategy.
  `JPanel(LayoutManager layout)`
  Create a new buffered JPanel with the specified layout manager
  `JPanel(LayoutManager layout, boolean isDoubleBuffered)`
  Creates a new JPanel with the specified layout manager and buffering strategy.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `AccessibleContext`
  `getAccessibleContext()`
  Gets the AccessibleContext associated with this JPanel.
  `PanelUI`
  `getUI()`
  Returns the look and feel (L&F) object that renders this component.
  `String`
  `getUIClassID()`
  Returns a string that specifies the name of the L&F class that renders this component.
  `protected String`
  `paramString()`
  Returns a string representation of this JPanel.
  `void`
  `setUI(PanelUI ui)`
  Sets the look and feel (L&F) object that renders this component.
  `void`
  `updateUI()`
  Resets the UI property with a value from the current look and feel.

  ### Methods declared in class JComponent

  `addAncestorListener, addNotify, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, disable, enable, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getActionMap, getAlignmentX, getAlignmentY, getAncestorListeners, getAutoscrolls, getBaseline, getBaselineResizeBehavior, getBorder, getBounds, getClientProperty, getComponentGraphics, getComponentPopupMenu, getConditionForKeyStroke, getDebugGraphicsOptions, getDefaultLocale, getFontMetrics, getGraphics, getHeight, getInheritsPopupMenu, getInputMap, getInputMap, getInputVerifier, getInsets, getInsets, getListeners, getLocation, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPopupLocation, getPreferredSize, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getTransferHandler, getVerifyInputWhenFocusTarget, getVetoableChangeListeners, getVisibleRect, getWidth, getX, getY, grabFocus, hide, isDoubleBuffered, isLightweightComponent, isManagingFocus, isOpaque, isOptimizedDrawingEnabled, isPaintingForPrint, isPaintingOrigin, isPaintingTile, isRequestFocusEnabled, isValidateRoot, paint, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, print, printAll, printBorder, printChildren, printComponent, processComponentKeyEvent, processKeyBinding, processKeyEvent, processMouseEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setActionMap, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setBorder, setComponentPopupMenu, setDebugGraphicsOptions, setDefaultLocale, setDoubleBuffered, setEnabled, setFocusTraversalKeys, setFont, setForeground, setInheritsPopupMenu, setInputMap, setInputVerifier, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setTransferHandler, setUI, setVerifyInputWhenFocusTarget, setVisible, unregisterKeyboardAction, update`

  ### Methods declared in class Container

  `add, add, add, add, add, addContainerListener, addImpl, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getComponentZOrder, getContainerListeners, getFocusTraversalKeys, getFocusTraversalPolicy, getLayout, getMousePosition, insets, invalidate, isAncestorOf, isFocusCycleRoot, isFocusCycleRoot, isFocusTraversalPolicyProvider, isFocusTraversalPolicySet, layout, list, list, locate, minimumSize, paintComponents, preferredSize, printComponents, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, setComponentZOrder, setFocusCycleRoot, setFocusTraversalPolicy, setFocusTraversalPolicyProvider, setLayout, transferFocusDownCycle, validate, validateTree`

  ### Methods declared in class 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, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getBackground, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getForeground, getGraphicsConfiguration, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocale, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getToolkit, getTreeLock, gotFocus, handleEvent, hasFocus, imageUpdate, inside, isBackgroundSet, isCursorSet, isDisplayable, isEnabled, isFocusable, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isPreferredSizeSet, 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, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, requestFocus, requestFocus, requestFocusInWindow, resize, resize, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setFocusable, setFocusTraversalKeysEnabled, setIgnoreRepaint, setLocale, setLocation, setLocation, setMixingCutoutShape, setName, setSize, setSize, show, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle`

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### JPanel

    public JPanel(LayoutManager layout, boolean isDoubleBuffered)
    Creates a new JPanel with the specified layout manager and buffering strategy.
    Parameters:
      `layout` - the LayoutManager to use
      `isDoubleBuffered` - a boolean, true for double-buffering, which uses additional memory space to achieve fast, flicker-free updates

  - ### JPanel

    public JPanel(LayoutManager layout)
    Create a new buffered JPanel with the specified layout manager
    Parameters:
      `layout` - the LayoutManager to use

  - ### JPanel

    public JPanel(boolean isDoubleBuffered)
    Creates a new `JPanel` with `FlowLayout` and the specified buffering strategy. If `isDoubleBuffered` is true, the `JPanel` will use a double buffer.
    Parameters:
      `isDoubleBuffered` - a boolean, true for double-buffering, which uses additional memory space to achieve fast, flicker-free updates

  - ### JPanel

    public JPanel()
    Creates a new `JPanel` with a double buffer and a flow layout.

- ## Method Details

  - ### updateUI

    public void updateUI()
    Resets the UI property with a value from the current look and feel.
    Overrides:
      `updateUI` in class `JComponent`
    See Also:
      - `JComponent.updateUI()`

  - ### getUI

    public PanelUI getUI()
    Returns the look and feel (L&F) object that renders this component.
    Overrides:
      `getUI` in class `JComponent`
    Returns:
      the PanelUI object that renders this component
    Since:
      1.4

  - ### setUI

    @BeanProperty(hidden=true, visualUpdate=true, description="The UI object that implements the Component's LookAndFeel.") public void setUI(PanelUI ui)
    Sets the look and feel (L&F) object that renders this component.
    Parameters:
      `ui` - the PanelUI L&F object
    Since:
      1.4
    See Also:
      - `UIDefaults.getUI(JComponent)`

  - ### getUIClassID

    @BeanProperty(bound=false, expert=true, description="A string that specifies the name of the L&F class.") public String getUIClassID()
    Returns a string that specifies the name of the L&F class that renders this component.
    Overrides:
      `getUIClassID` in class `JComponent`
    Returns:
      the string "PanelUI"
    See Also:
      - `JComponent.getUIClassID()`
      - `UIDefaults.getUI(JComponent)`

  - ### paramString

    protected String paramString()
    Returns a string representation of this JPanel. 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 JPanel.

  - ### getAccessibleContext

    @BeanProperty(bound=false) public AccessibleContext getAccessibleContext()
    Gets the AccessibleContext associated with this JPanel. For JPanels, the AccessibleContext takes the form of an AccessibleJPanel. A new AccessibleJPanel instance is created if necessary.
    Specified by:
      `getAccessibleContext` in interface `Accessible`
    Overrides:
      `getAccessibleContext` in class `Component`
    Returns:
      an AccessibleJPanel that serves as the AccessibleContext of this JPanel