Java v1.02 only supports the "voice format" of the .au sound files. This is also know as "?-law, 8/16-bit, mono, 8000hz sample rate"
The Canvas class of java.awt is used to provide custom drawing and event handling. It provides a general GUI component for drawing images and text on the screen. It does not support any drawing methods of its own, but provides access to a Graphics object through its paint() method. The paint() method is invoked upon the creation and update of a canvas so that the Graphics object associated with a Canvas object can be updated.
Swing provides a richer set of components than AWT. They are 100% Java-based. AWT on the other hand was developed with the mind set that if a component or capability of a component werent available on one platform, it wouldnt be available on any platform. Due to the peer-based nature of AWT, what might work on one implementation might not work on another, as the peer-integration might not be as robust. There are a few other advantages to Swing over AWT:
? Swing provides both additional components and added functionality to AWT-replacement components
? Swing components can change their appearance based on the current "look and feel" library that's being used.
? Swing components follow the Model-View-Controller (MVC) paradigm, and thus can provide a much more flexible UI.
? Swing provides "extras" for components, such as:
? Icons on many components
? Decorative borders for components
? Tool tips for components
? Swing components are lightweight (less resource intensive than AWT)
? Swing provides built-in double buffering
? Swing provides paint debugging support for when you build your own components
Swing also has a few disadvantages:
? It requires Java 2 or a separate JAR file
? If you're not very careful when programming, it can be slower than AWT (all components are drawn)
? Swing components that look like native components might not act exactly like native components
JComponent (except top-level containers)
We can use the java.net.URLConnection and java.net.URL classes to open a standard HTTP connection and "tunnel" to the web server. The server then passes this information to the servlet in the normal way. Basically, the applet pretends to be a web browser, and the servlet doesn't know the difference. As far as the servlet is concerned, the applet is just another HTTP client.
The simplest method is to use the static variables of a shared class since there's only one instance of the class and hence only one copy of its static variables. A slightly more reliable method relies on the fact that all the applets on a given page share the same AppletContext. We obtain this applet context as follows:
AppletContext ac = getAppletContext();
AppletContext provides applets with methods such as getApplet(name), getApplets(),getAudioClip, getImage, showDocument and showStatus().
Whenever a screen needs redrawing (e.g., upon creation, resizing, validating) the update method is called. By default, the update method clears the screen and then calls the paint method, which normally contains all the drawing code.
drawString( ) method is used to output a string to an applet. This method is included in the paint method of the Applet.
Following are the steps involved in Applet development:
? Create/Edit a Java source file. This file must contain a class which extends Applet class.
? Compile your program using javac
? Execute the appletviewer, specifying the name of your applet?s source file or html file. In case the applet information is stored in html file then Applet can be invoked using java enabled web browser.
The following are the Applet?s information methods: getAppletInfo() method: Returns a string describing the applet, its author, copyright information, etc. getParameterInfo( ) method: Returns an array of string describing the applet?s parameters.
Java v1.02 only supports the "voice format" of the .au sound files. This is also know as "µ-law, 8/16-bit, mono, 8000hz sample rate"
The applet stub interface provides the means by which an applet and the browser communicate. Your code will not typically implement this interface.
Applet class consists of a single class, the Applet class and three interfaces: AppletContext, AppletStub, and AudioClip.
Use the getSize() method, which the Applet class inherits from the Component class in the Java.awt package. The getSize() method returns the size of the applet as a Dimension object, from which you extract separate width, height fields. The following code snippet explains this:
Dimension dim = getSize();
int appletwidth = dim.width();
int appletheight = dim.height();
Ask the applet for its applet context and invoke showDocument() on that context object.
AppletContext context = getAppletContext();
targetURL = new URL(URLString);
catch (MalformedURLException e)
// Code for recover from the exception
context. showDocument (targetURL);
Name your applets inside the Applet tag and invoke AppletContext?s getApplet() method in your applet code to obtain references to the
other applets on the page.
Use the parseInt() method in the Integer Class, the Float(String) constructor or parseFloat() method in the Class Float, or the
Double(String) constructor or parseDoulbl() method in the class Double.
We can pass parameters to an applet using <param> tag in the following way:
? <param name=?param1? value=?value1?>
? <param name=?param2? value=?value2?>
Access those parameters inside the applet is done by calling getParameter() method inside the applet. Note that getParameter() method returns String value corresponding to the parameter name.
Following are the main differences:
Application: Stand Alone, doesn?t need
web-browser. Applet: Needs no explicit installation on local machine. Can be transferred through Internet on to the local machine and may run as part of web-browser. Application: Execution starts with main() method. Doesn?t work if main is not there. Applet: Execution starts with init() method. Application: May or may not be a GUI. Applet: Must run within a GUI (Using AWT). This is essential feature of applets.
When an applet begins, the AWT calls the following methods, in this sequence:
When an applet is terminated, the following sequence of method calls takes place :
methods in the life cycle of an Applet:
? init() method - called when an applet is first loaded. This method is called only once in the entire cycle of an applet. This method usually intialize the variables to be used in the applet.
? start( ) method - called each time an applet is started.
? paint() method - called when the applet is minimized or refreshed. This method is used for drawing different strings, figures, and images on the applet window.
? stop( ) method - called when the browser moves off the applet?s page.
? destroy( ) method - called when the browser is finished with the applet.
? public void init() : Initialization method called once by browser.
? public void start() : Method called after init() and contains code to start processing. If the user leaves the page and returns without killing the current browser session, the start () method is called without being preceded by init ().
? public void stop() : Stops all processing started by start (). Done if user moves off page.
? public void destroy() : Called if current browser session is being terminated. Frees all resources used by applet.
Since 2.00 version our applets support an user-defined delimiter for the menu arguments. To modify the default delimiter add the following parameter (you can use any character as a delimiter):
<param name="delimiter" value="~">
and use it within "menuItems":
<param name="menuItems" value="
1. Place the .class file in the directory containing the HTML document into which you want to insert the applet.
2. Copy the <applet>...</applet> tag from your applet implementation or examples to the clipboard.
3. In FrontPage select the "HTML" tab from the lower left hand corner.
4. Paste the <applet>...</applet> tag in an appropriate place between the <body> and </body> tags. You'll find a gray box with the aqua letter "J" in the "Normal" view indicating the the applet tag has been inserted.
5. To see the applet appearance select the "Preview" tab.
Write my initialization code in the applets init method or applet constructor.
Applets are small programs transferred through Internet, automatically installed and run as part of web-browser. Applets implements functionality of a client. Applet is a dynamic and interactive program that runs inside a Web page displayed by a Java-capable browser. We don?t have the concept of Constructors in Applets. Applets can be invoked either through browser or through Appletviewer utility provided by JDK.