/* * Copyright (c) 1995, 2006, Oracle and/or its affiliates. All rights reserved. * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. * * * * * * * * * * * * * * * * * * * * */package java.applet; import java.awt.*;import java.awt.image.ColorModel;import java.io.IOException;import java.io.ObjectInputStream;import java.net.URL;import java.net.MalformedURLException;import java.util.Hashtable;import java.util.Locale;import javax.accessibility.*; /** * An applet is a small program that is intended not to be run on * its own, but rather to be embedded inside another application. * <p> * The <code>Applet</code> 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 <code>Applet</code> class provides a standard * interface between applets and their environment. * * @author      Arthur van Hoff * @author      Chris Warth * @since       JDK1.0 */public class Applet extends Panel {     /**     * Constructs a new Applet.     * <p>     * Note: Many methods in <code>java.applet.Applet</code>     * may be invoked by the applet only after the applet is     * fully constructed; applet should avoid calling methods     * in <code>java.applet.Applet</code> in the constructor.     *     * @exception HeadlessException if GraphicsEnvironment.isHeadless()     * returns true.     * @see java.awt.GraphicsEnvironment#isHeadless     * @since 1.4     */    public Applet() throws HeadlessException {        if (GraphicsEnvironment.isHeadless()) {            throw new HeadlessException();        }    }     /**     * Applets can be serialized but the following conventions MUST be followed:     *     * Before Serialization:     * An applet must be in STOPPED state.     *     * After Deserialization:     * The applet will be restored in STOPPED state (and most clients will     * likely move it into RUNNING state).     * The stub field will be restored by the reader.     */    transient private AppletStub stub;     /* version ID for serialized form. */    private static final long serialVersionUID = -5836846270535785031L;     /**     * Read an applet from an object input stream.     * @exception HeadlessException if     * <code>GraphicsEnvironment.isHeadless()</code> returns     * <code>true</code>     * @serial     * @see java.awt.GraphicsEnvironment#isHeadless     * @since 1.4     */    private void readObject(ObjectInputStream s)        throws ClassNotFoundException, IOException, HeadlessException {        if (GraphicsEnvironment.isHeadless()) {            throw new HeadlessException();        }        s.defaultReadObject();    }     /**     * Sets this applet's stub. This is done automatically by the system.     * <p>If there is a security manager, its <code> checkPermission </code>     * method is called with the     * <code>AWTPermission("setAppletStub")</code>     * permission if a stub has already been set.     * @param   stub   the new stub.     * @exception SecurityException if the caller cannot set the stub     */    public final void setStub(AppletStub stub) {        if (this.stub != null) {            SecurityManager s = System.getSecurityManager();            if (s != null) {                s.checkPermission(new AWTPermission("setAppletStub"));            }        }        this.stub = (AppletStub)stub;    }     /**     * Determines if this applet is active. An applet is marked active     * just before its <code>start</code> method is called. It becomes     * inactive just before its <code>stop</code> method is called.     *     * @return  <code>true</code> if the applet is active;     *          <code>false</code> otherwise.     * @see     java.applet.Applet#start()     * @see     java.applet.Applet#stop()     */    public boolean isActive() {        if (stub != null) {            return stub.isActive();        } else {        // If stub field not filled in, applet never active            return false;        }    }     /**     * Gets the URL of the document in which this applet is embedded.     * For example, suppose an applet is contained     * within the document:     * <blockquote><pre>     *    http://java.sun.com/products/jdk/1.2/index.html     * </pre></blockquote>     * The document base is:     * <blockquote><pre>     *    http://java.sun.com/products/jdk/1.2/index.html     * </pre></blockquote>     *     * @return  the {@link java.net.URL} of the document that contains this     *          applet.     * @see     java.applet.Applet#getCodeBase()     */    public URL getDocumentBase() {        return stub.getDocumentBase();    }     /**     * Gets the base URL. This is the URL of the directory which contains this applet.     *     * @return  the base {@link java.net.URL} of     *          the directory which contains this applet.     * @see     java.applet.Applet#getDocumentBase()     */    public URL getCodeBase() {        return stub.getCodeBase();    }     /**     * Returns the value of the named parameter in the HTML tag. For     * example, if this applet is specified as     * <blockquote><pre>     * &lt;applet code="Clock" width=50 height=50&gt;     * &lt;param name=Color value="blue"&gt;     * &lt;/applet&gt;     * </pre></blockquote>     * <p>     * then a call to <code>getParameter("Color")</code> returns the     * value <code>"blue"</code>.     * <p>     * The <code>name</code> argument is case insensitive.     *     * @param   name   a parameter name.     * @return  the value of the named parameter,     *          or <code>null</code> if not set.     */     public String getParameter(String name) {         return stub.getParameter(name);     }     /**     * Determines this applet's context, which allows the applet to     * query and affect the environment in which it runs.     * <p>     * This environment of an applet represents the document that     * contains the applet.     *     * @return  the applet's context.     */    public AppletContext getAppletContext() {        return stub.getAppletContext();    }     /**     * Requests that this applet be resized.     *     * @param   width    the new requested width for the applet.     * @param   height   the new requested height for the applet.     */    public void resize(int width, int height) {        Dimension d = size();        if ((d.width != width) || (d.height != height)) {            super.resize(width, height);            if (stub != null) {                stub.appletResize(width, height);            }        }    }     /**     * Requests that this applet be resized.     *     * @param   d   an object giving the new width and height.     */    public void resize(Dimension d) {        resize(d.width, d.height);    }     /**     * Indicates if this container is a validate root.     * <p>     * {@code Applet} objects are the validate roots, and, therefore, they     * override this method to return {@code true}.     *     * @return {@code true}     * @since 1.7     * @see java.awt.Container#isValidateRoot     */    @Override    public boolean isValidateRoot() {        return true;    }     /**     * 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.     *     * @param   msg   a string to display in the status window.     */    public void showStatus(String msg) {        getAppletContext().showStatus(msg);    }     /**     * Returns an <code>Image</code> object that can then be painted on     * the screen. The <code>url</code> that is passed as an argument     * must specify an absolute URL.     * <p>     * 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.     *     * @param   url   an absolute URL giving the location of the image.     * @return  the image at the specified URL.     * @see     java.awt.Image     */    public Image getImage(URL url) {        return getAppletContext().getImage(url);    }     /**     * Returns an <code>Image</code> object that can then be painted on     * the screen. The <code>url</code> argument must specify an absolute     * URL. The <code>name</code> argument is a specifier that is     * relative to the <code>url</code> argument.     * <p>     * 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.     *     * @param   url    an absolute URL giving the base location of the image.     * @param   name   the location of the image, relative to the     *                 <code>url</code> argument.     * @return  the image at the specified URL.     * @see     java.awt.Image     */    public Image getImage(URL url, String name) {        try {            return getImage(new URL(url, name));        } catch (MalformedURLException e) {            return null;        }    }     /**     * Get an audio clip from the given URL.     *     * @param url points to the audio clip     * @return the audio clip at the specified URL.     *     * @since       1.2     */    public final static AudioClip newAudioClip(URL url) {        return new sun.applet.AppletAudioClip(url);    }     /**     * Returns the <code>AudioClip</code> object specified by the     * <code>URL</code> argument.     * <p>     * 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.     *     * @param   url  an absolute URL giving the location of the audio clip.     * @return  the audio clip at the specified URL.     * @see     java.applet.AudioClip     */    public AudioClip getAudioClip(URL url) {        return getAppletContext().getAudioClip(url);    }     /**     * Returns the <code>AudioClip</code> object specified by the     * <code>URL</code> and <code>name</code> arguments.     * <p>     * 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.     *     * @param   url    an absolute URL giving the base location of the     *                 audio clip.     * @param   name   the location of the audio clip, relative to the     *                 <code>url</code> argument.     * @return  the audio clip at the specified URL.     * @see     java.applet.AudioClip     */    public AudioClip getAudioClip(URL url, String name) {        try {            return getAudioClip(new URL(url, name));        } catch (MalformedURLException e) {            return null;        }    }     /**     * Returns information about this applet. An applet should override     * this method to return a <code>String</code> containing information     * about the author, version, and copyright of the applet.     * <p>     * The implementation of this method provided by the     * <code>Applet</code> class returns <code>null</code>.     *     * @return  a string containing information about the author, version, and     *          copyright of the applet.     */    public String getAppletInfo() {        return null;    }     /**     * Gets the locale of the applet. It allows the applet     * to maintain its own locale separated from the locale     * of the browser or appletviewer.     *     * @return  the locale of the applet; if no locale has     *          been set, the default locale is returned.     * @since   JDK1.1     */    public Locale getLocale() {      Locale locale = super.getLocale();      if (locale == null) {        return Locale.getDefault();      }      return locale;    }     /**     * Returns information about the parameters that are understood by     * this applet. An applet should override this method to return an     * array of <code>Strings</code> describing these parameters.     * <p>     * Each element of the array should be a set of three     * <code>Strings</code> containing the name, the type, and a     * description. For example:     * <p><blockquote><pre>     * String pinfo[][] = {     *   {"fps",    "1-10",    "frames per second"},     *   {"repeat", "boolean", "repeat image loop"},     *   {"imgs",   "url",     "images directory"}     * };     * </pre></blockquote>     * <p>     * The implementation of this method provided by the     * <code>Applet</code> class returns <code>null</code>.     *     * @return  an array describing the parameters this applet looks for.     */    public String[][] getParameterInfo() {        return null;    }     /**     * Plays the audio clip at the specified absolute URL. Nothing     * happens if the audio clip cannot be found.     *     * @param   url   an absolute URL giving the location of the audio clip.     */    public void play(URL url) {        AudioClip clip = getAudioClip(url);        if (clip != null) {            clip.play();        }    }     /**     * Plays the audio clip given the URL and a specifier that is     * relative to it. Nothing happens if the audio clip cannot be found.     *     * @param   url    an absolute URL giving the base location of the     *                 audio clip.     * @param   name   the location of the audio clip, relative to the     *                 <code>url</code> argument.     */    public void play(URL url, String name) {        AudioClip clip = getAudioClip(url, name);        if (clip != null) {            clip.play();        }    }     /**     * 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 <code>start</code> method is     * called.     * <p>     * A subclass of <code>Applet</code> should override this method if     * it has initialization to perform. For example, an applet with     * threads would use the <code>init</code> method to create the     * threads and the <code>destroy</code> method to kill them.     * <p>     * The implementation of this method provided by the     * <code>Applet</code> class does nothing.     *     * @see     java.applet.Applet#destroy()     * @see     java.applet.Applet#start()     * @see     java.applet.Applet#stop()     */    public void init() {    }     /**     * Called by the browser or applet viewer to inform     * this applet that it should start its execution. It is called after     * the <code>init</code> method and each time the applet is revisited     * in a Web page.     * <p>     * A subclass of <code>Applet</code> 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 <code>start</code> method to     * resume animation, and the <code>stop</code> method to suspend the     * animation.     * <p>     * Note: some methods, such as <code>getLocationOnScreen</code>, can only     * provide meaningful results if the applet is showing.  Because     * <code>isShowing</code> returns <code>false</code> when the applet's     * <code>start</code> is first called, methods requiring     * <code>isShowing</code> to return <code>true</code> should be called from     * a <code>ComponentListener</code>.     * <p>     * The implementation of this method provided by the     * <code>Applet</code> class does nothing.     *     * @see     java.applet.Applet#destroy()     * @see     java.applet.Applet#init()     * @see     java.applet.Applet#stop()     * @see     java.awt.Component#isShowing()     * @see     java.awt.event.ComponentListener#componentShown(java.awt.event.ComponentEvent)     */    public void start() {    }     /**     * 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.     * <p>     * A subclass of <code>Applet</code> 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

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