Applet (Java Platform SE 8 )
Keywords: java.applet.Applet class
Date: 2016-12-09

java.applet

## Class Applet

- java.lang.Object
- - java.awt.Component
  - - java.awt.Container
    - - java.awt.Panel
      - - java.applet.Applet

- All Implemented Interfaces:
    ImageObserver, MenuContainer, Serializable, Accessible
  Direct Known Subclasses:
    JApplet

      public class Applet
      extends Panel

  An applet is a small program that is intended not to be run on its own, but rather to be embedded inside another application.

  The `Applet` class must be the superclass of any applet that is to be embedded in a Web page or viewed by the Java Applet Viewer. The `Applet` class provides a standard interface between applets and their environment.

  Since:
    JDK1.0
  See Also:
    Serialized Form

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `protected class` | `Applet.AccessibleApplet` This class implements accessibility support for the `Applet` class.

    - ### Nested classes/interfaces inherited from class java.awt.Panel

      `Panel.AccessibleAWTPanel`

    - ### Nested classes/interfaces inherited from class java.awt.Container

      `Container.AccessibleAWTContainer`

    - ### Nested classes/interfaces inherited from class java.awt.Component

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

  - ### Field Summary

    - ### 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

    Constructors
    Constructor and Description
    `Applet()` Constructs a new Applet.

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `destroy()` Called by the browser or applet viewer to inform this applet that it is being reclaimed and that it should destroy any resources that it has allocated.
    `AccessibleContext` | `getAccessibleContext()` Gets the AccessibleContext associated with this Applet.
    `AppletContext` | `getAppletContext()` Determines this applet's context, which allows the applet to query and affect the environment in which it runs.
    `String` | `getAppletInfo()` Returns information about this applet.
    `AudioClip` | `getAudioClip(URL url)` Returns the `AudioClip` object specified by the `URL` argument.
    `AudioClip` | `getAudioClip(URL url, String name)` Returns the `AudioClip` object specified by the `URL` and `name` arguments.
    `URL` | `getCodeBase()` Gets the base URL.
    `URL` | `getDocumentBase()` Gets the URL of the document in which this applet is embedded.
    `Image` | `getImage(URL url)` Returns an `Image` object that can then be painted on the screen.
    `Image` | `getImage(URL url, String name)` Returns an `Image` object that can then be painted on the screen.
    `Locale` | `getLocale()` Gets the locale of the applet.
    `String` | `getParameter(String name)` Returns the value of the named parameter in the HTML tag.
    `String[][]` | `getParameterInfo()` Returns information about the parameters that are understood by this applet.
    `void` | `init()` Called by the browser or applet viewer to inform this applet that it has been loaded into the system.
    `boolean` | `isActive()` Determines if this applet is active.
    `boolean` | `isValidateRoot()` Indicates if this container is a validate root.
    `static AudioClip` | `newAudioClip(URL url)` Get an audio clip from the given URL.
    `void` | `play(URL url)` Plays the audio clip at the specified absolute URL.
    `void` | `play(URL url, String name)` Plays the audio clip given the URL and a specifier that is relative to it.
    `void` | `resize(Dimension d)` Requests that this applet be resized.
    `void` | `resize(int width, int height)` Requests that this applet be resized.
    `void` | `setStub(AppletStub stub)` Sets this applet's stub.
    `void` | `showStatus(String msg)` Requests that the argument string be displayed in the "status window".
    `void` | `start()` Called by the browser or applet viewer to inform this applet that it should start its execution.
    `void` | `stop()` Called by the browser or applet viewer to inform this applet that it should stop its execution.

    - ### Methods inherited from class java.awt.Panel

      `addNotify`

    - ### Methods inherited from class java.awt.Container

      `add, add, add, add, add, addContainerListener, addImpl, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getAlignmentX, getAlignmentY, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getComponentZOrder, getContainerListeners, getFocusTraversalKeys, getFocusTraversalPolicy, getInsets, getLayout, getListeners, getMaximumSize, getMinimumSize, getMousePosition, getPreferredSize, insets, invalidate, isAncestorOf, isFocusCycleRoot, isFocusCycleRoot, isFocusTraversalPolicyProvider, isFocusTraversalPolicySet, layout, list, list, locate, minimumSize, paint, paintComponents, paramString, preferredSize, print, printComponents, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, removeNotify, setComponentZOrder, setFocusCycleRoot, setFocusTraversalKeys, setFocusTraversalPolicy, setFocusTraversalPolicyProvider, setFont, setLayout, transferFocusDownCycle, update, 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, contains, createImage, createImage, createVolatileImage, createVolatileImage, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getBackground, getBaseline, getBaselineResizeBehavior, getBounds, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocation, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPeer, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, isBackgroundSet, isCursorSet, isDisplayable, isDoubleBuffered, isEnabled, isFocusable, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isPreferredSizeSet, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, printAll, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, reshape, revalidate, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFocusable, setFocusTraversalKeysEnabled, setForeground, setIgnoreRepaint, setLocale, setLocation, setLocation, setMaximumSize, setMinimumSize, setName, setPreferredSize, setSize, setSize, setVisible, show, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle`

    - ### Methods inherited from class java.lang.Object

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

- - ### Constructor Detail

    - #### Applet

          public Applet()
                 throws HeadlessException

      Constructs a new Applet.

      Note: Many methods in `java.applet.Applet` may be invoked by the applet only after the applet is fully constructed; applet should avoid calling methods in `java.applet.Applet` in the constructor.

      Throws:
        `HeadlessException` - if GraphicsEnvironment.isHeadless() returns true.
      Since:
        1.4
      See Also:
        `GraphicsEnvironment.isHeadless()`

  - ### Method Detail

    - #### setStub

          public final void setStub(AppletStub stub)

      Sets this applet's stub. This is done automatically by the system.

      If there is a security manager, its `checkPermission` method is called with the `AWTPermission("setAppletStub")` permission if a stub has already been set.

      Parameters:
        `stub` - the new stub.
      Throws:
        `SecurityException` - if the caller cannot set the stub

    - #### isActive

          public boolean isActive()

      Determines if this applet is active. An applet is marked active just before its `start` method is called. It becomes inactive just before its `stop` method is called.
      Returns:
        `true` if the applet is active; `false` otherwise.
      See Also:
        `start()`, `stop()`

    - #### getDocumentBase

          public URL getDocumentBase()

      Gets the URL of the document in which this applet is embedded. For example, suppose an applet is contained within the document:

      >         http://www.oracle.com/technetwork/java/index.html

      The document base is:

      >         http://www.oracle.com/technetwork/java/index.html

      Returns:
        the `URL` of the document that contains this applet.
      See Also:
        `getCodeBase()`

    - #### getCodeBase

          public URL getCodeBase()

      Gets the base URL. This is the URL of the directory which contains this applet.
      Returns:
        the base `URL` of the directory which contains this applet.
      See Also:
        `getDocumentBase()`

    - #### getParameter

          public String getParameter(String name)

      Returns the value of the named parameter in the HTML tag. For example, if this applet is specified as

      >      <applet code="Clock" width=50 height=50>
      >      <param name=Color value="blue">
      >      </applet>

      then a call to `getParameter("Color")` returns the value `"blue"`.

      The `name` argument is case insensitive.

      Parameters:
        `name` - a parameter name.
      Returns:
        the value of the named parameter, or `null` if not set.

    - #### getAppletContext

          public AppletContext getAppletContext()

      Determines this applet's context, which allows the applet to query and affect the environment in which it runs.

      This environment of an applet represents the document that contains the applet.

      Returns:
        the applet's context.

    - #### resize

          public void resize(int width,
                             int height)

      Requests that this applet be resized.
      Overrides:
        `resize` in class `Component`
      Parameters:
        `width` - the new requested width for the applet.
        `height` - the new requested height for the applet.

    - #### resize

          public void resize(Dimension d)

      Requests that this applet be resized.
      Overrides:
        `resize` in class `Component`
      Parameters:
        `d` - an object giving the new width and height.

    - #### isValidateRoot

          public boolean isValidateRoot()

      Indicates if this container is a validate root.

      `Applet` objects are the validate roots, and, therefore, they override this method to return `true`.

      Overrides:
        `isValidateRoot` in class `Container`
      Returns:
        `true`
      Since:
        1.7
      See Also:
        `Container.isValidateRoot()`

    - #### showStatus

          public void showStatus(String msg)

      Requests that the argument string be displayed in the "status window". Many browsers and applet viewers provide such a window, where the application can inform users of its current state.
      Parameters:
        `msg` - a string to display in the status window.

    - #### getImage

          public Image getImage(URL url)

      Returns an `Image` object that can then be painted on the screen. The `url` that is passed as an argument must specify an absolute URL.

      This method always returns immediately, whether or not the image exists. When this applet attempts to draw the image on the screen, the data will be loaded. The graphics primitives that draw the image will incrementally paint on the screen.

      Parameters:
        `url` - an absolute URL giving the location of the image.
      Returns:
        the image at the specified URL.
      See Also:
        `Image`

    - #### getImage

          public Image getImage(URL url,
                                String name)

      Returns an `Image` object that can then be painted on the screen. The `url` argument must specify an absolute URL. The `name` argument is a specifier that is relative to the `url` argument.

      This method always returns immediately, whether or not the image exists. When this applet attempts to draw the image on the screen, the data will be loaded. The graphics primitives that draw the image will incrementally paint on the screen.

      Parameters:
        `url` - an absolute URL giving the base location of the image.
        `name` - the location of the image, relative to the `url` argument.
      Returns:
        the image at the specified URL.
      See Also:
        `Image`

    - #### newAudioClip

          public static final AudioClip newAudioClip(URL url)

      Get an audio clip from the given URL.
      Parameters:
        `url` - points to the audio clip
      Returns:
        the audio clip at the specified URL.
      Since:
        1.2

    - #### getAudioClip

          public AudioClip getAudioClip(URL url)

      Returns the `AudioClip` object specified by the `URL` argument.

      This method always returns immediately, whether or not the audio clip exists. When this applet attempts to play the audio clip, the data will be loaded.

      Parameters:
        `url` - an absolute URL giving the location of the audio clip.
      Returns:
        the audio clip at the specified URL.
      See Also:
        `AudioClip`

    - #### getAudioClip

          public AudioClip getAudioClip(URL url,
                                        String name)

      Returns the `AudioClip` object specified by the `URL` and `name` arguments.

      This method always returns immediately, whether or not the audio clip exists. When this applet attempts to play the audio clip, the data will be loaded.

      Parameters:
        `url` - an absolute URL giving the base location of the audio clip.
        `name` - the location of the audio clip, relative to the `url` argument.
      Returns:
        the audio clip at the specified URL.
      See Also:
        `AudioClip`

    - #### getAppletInfo

          public String getAppletInfo()

      Returns information about this applet. An applet should override this method to return a `String` containing information about the author, version, and copyright of the applet.

      The implementation of this method provided by the `Applet` class returns `null`.

      Returns:
        a string containing information about the author, version, and copyright of the applet.

    - #### getLocale

          public Locale getLocale()

      Gets the locale of the applet. It allows the applet to maintain its own locale separated from the locale of the browser or appletviewer.
      Overrides:
        `getLocale` in class `Component`
      Returns:
        the locale of the applet; if no locale has been set, the default locale is returned.
      Since:
        JDK1.1
      See Also:
        `Component.setLocale(java.util.Locale)`

    - #### getParameterInfo

          public String[][] getParameterInfo()

      Returns information about the parameters that are understood by this applet. An applet should override this method to return an array of `Strings` describing these parameters.

      Each element of the array should be a set of three `Strings` containing the name, the type, and a description. For example:

      >      String pinfo[][] = {
      >        {"fps",    "1-10",    "frames per second"},
      >        {"repeat", "boolean", "repeat image loop"},
      >        {"imgs",   "url",     "images directory"}
      >      };

      The implementation of this method provided by the `Applet` class returns `null`.

      Returns:
        an array describing the parameters this applet looks for.

    - #### play

          public void play(URL url)

      Plays the audio clip at the specified absolute URL. Nothing happens if the audio clip cannot be found.
      Parameters:
        `url` - an absolute URL giving the location of the audio clip.

    - #### play

          public void play(URL url,
                           String name)

      Plays the audio clip given the URL and a specifier that is relative to it. Nothing happens if the audio clip cannot be found.
      Parameters:
        `url` - an absolute URL giving the base location of the audio clip.
        `name` - the location of the audio clip, relative to the `url` argument.

    - #### init

          public void init()

      Called by the browser or applet viewer to inform this applet that it has been loaded into the system. It is always called before the first time that the `start` method is called.

      A subclass of `Applet` should override this method if it has initialization to perform. For example, an applet with threads would use the `init` method to create the threads and the `destroy` method to kill them.

      The implementation of this method provided by the `Applet` class does nothing.

      See Also:
        `destroy()`, `start()`, `stop()`

    - #### start

          public void start()

      Called by the browser or applet viewer to inform this applet that it should start its execution. It is called after the `init` method and each time the applet is revisited in a Web page.

      A subclass of `Applet` should override this method if it has any operation that it wants to perform each time the Web page containing it is visited. For example, an applet with animation might want to use the `start` method to resume animation, and the `stop` method to suspend the animation.

      Note: some methods, such as `getLocationOnScreen`, can only provide meaningful results if the applet is showing. Because `isShowing` returns `false` when the applet's `start` is first called, methods requiring `isShowing` to return `true` should be called from a `ComponentListener`.

      The implementation of this method provided by the `Applet` class does nothing.

      See Also:
        `destroy()`, `init()`, `stop()`, `Component.isShowing()`, `ComponentListener.componentShown(java.awt.event.ComponentEvent)`

    - #### stop

          public void stop()

      Called by the browser or applet viewer to inform this applet that it should stop its execution. It is called when the Web page that contains this applet has been replaced by another page, and also just before the applet is to be destroyed.

      A subclass of `Applet` should override this method if it has any operation that it wants to perform each time the Web page containing it is no longer visible. For example, an applet with animation might want to use the `start` method to resume animation, and the `stop` method to suspend the animation.

      The implementation of this method provided by the `Applet` class does nothing.

      See Also:
        `destroy()`, `init()`

    - #### destroy

          public void destroy()

      Called by the browser or applet viewer to inform this applet that it is being reclaimed and that it should destroy any resources that it has allocated. The `stop` method will always be called before `destroy`.

      A subclass of `Applet` should override this method if it has any operation that it wants to perform before it is destroyed. For example, an applet with threads would use the `init` method to create the threads and the `destroy` method to kill them.

      The implementation of this method provided by the `Applet` class does nothing.

      See Also:
        `init()`, `start()`, `stop()`

    - #### getAccessibleContext

          public AccessibleContext getAccessibleContext()

      Gets the AccessibleContext associated with this Applet. For applets, the AccessibleContext takes the form of an AccessibleApplet. A new AccessibleApplet instance is created if necessary.
      Specified by:
        `getAccessibleContext` in interface `Accessible`
      Overrides:
        `getAccessibleContext` in class `Panel`
      Returns:
        an AccessibleApplet that serves as the AccessibleContext of this Applet
      Since:
        1.3

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