Java™ How to Program, Sixth Edition - Part20

Few weeks back i started reading Java™ How to Program, Sixth Edition By H. M. Deitel - Deitel & Associates, Inc., P. J. Deitel - Deitel & Associates, Inc.

Nice book written By H. M. Deitel - Deitel & Associates, Inc., P. J. Deitel - Deitel & Associates, Inc.

I wanted to share few quotations found the book from the 20th chapter.

1) Applets are Java programs that can be embedded in HyperText Markup Language (HTML) documents.

2) When a browser loads a Web page containing an applet, the applet downloads into the Web browser and executes.

3) The browser that executes an applet is generically known as the applet container. The JDK includes the appletviewer applet container for testing applets before you embed them in a Web page.

4) To reexecute an applet in the appletviewer, click the appletviewer's Applet menu and select the Reload menu item.

5) To terminate the appletviewer, select Quit from the appletviewer's Applet menu.

6) Every Java applet is a graphical user interface on which you can place GUI components or draw.

7) Class JApplet from package javax.swing is used to create applets.

8) An applet container can create only objects of classes that are public and extend JApplet (or the Applet class from early versions of Java).

9) An applet container expects every Java applet to have methods named init, start, paint, stop and destroy, each of which is declared in class JApplet. Each new applet class you create inherits default implementations of these methods from class JApplet.

10) When an applet container loads an applet, the container creates an object of the applet's type, then calls the applet's init, start and paint methods. If you do not declare these methods in your applet, the applet container calls the inherited versions.

11) The superclass methods init and start have empty bodies, so they do not perform any tasks. The superclass method paint does not draw anything on the applet.

12) To enable an applet to draw, override its method paint. You do not call method paint explicitly in an applet. Rather, the applet container calls paint to tell the applet when to draw, and the applet container is responsible for passing a Graphics object as an argument.

13) The first statement in method paint should be a call to the superclass version of method paint. Omitting this can cause subtle drawing errors in applets that combine drawing and GUI components.

14) Before you can execute an applet, you must create an HTML (HyperText Markup Language) document that specifies which applet to execute in the applet container. Typically, an HTML document ends with an ".html" or ".htm" file-name extension.

15) Most HTML elements are delimited by pairs of tags. All HTML tags begin with a left angle bracket, <, and end with a right angle bracket, >.

16) An applet element tells the applet container to load a specific applet and defines the size of the applet's display area (its width and height in pixels) in the applet container.

17) Normally, an applet and its corresponding HTML document are stored in the same directory.

18) Typically, a browser loads an HTML document from a computer (other than your own) connected to the Internet.

19) When an applet container encounters an HTML document that contains an applet, the applet container automatically loads the applet's .class file(s) from the same directory on the computer in which the HTML document resides.

20) The appletviewer understands only the and HTML tags and ignores all other tags in the document.

21) The appletviewer is an ideal place to test an applet and ensure that it executes properly. Once the applet's execution is verified, you can add its HTML tags to a Web page that others can view in their Web browsers.

22) There are five applet methods that are called by the applet container from the time the applet is loaded into the browser to the time that the applet is terminated by the browser. These methods correspond to various aspects of an applet's life cycle.

23) Method init is called once by the applet container when an applet is loaded for execution. This method initializes the applet.

24) Method start is called by the applet container after method init completes execution. In addition, if the user browses to another Web site and later returns to the applet's HTML page, method start is called again.

25) Method paint is called by the applet container after methods init and start. Method paint is also called when the applet needs to be repainted.

26) Method stop is called by the applet container when the user leaves the applet's Web page by browsing to another Web page.

27) Method destroy is called by the applet container when the applet is being removed from memory. This occurs when the user exits the browsing session by closing all the browser windows and may also occur at the browser's discretion when the user has browsed to other Web pages.

About the Authors

Dr. Harvey M. Deitel, Chairman and Chief Strategy Officer of Deitel & Associates, Inc., has 43 years experience in the computing field, including extensive industry and academic experience. Dr. Deitel earned B.S. and M.S. degrees from the Massachusetts Institute of Technology and a Ph.D. from Boston University. He worked on the pioneering virtual-memory operating-systems projects at IBM and MIT that developed techniques now widely implemented in systems such as UNIX, Linux and Windows XP. He has 20 years of college teaching experience, including earning tenure and serving as the Chairman of the Computer Science Department at Boston College before founding Deitel & Associates, Inc., with his son, Paul J. Deitel. He and Paul are the co-authors of several dozen books and multimedia packages and they are writing many more. With translations published in Japanese, German, Russian, Spanish, Traditional Chinese, Simplified Chinese, Korean, French, Polish, Italian, Portuguese, Greek, Urdu and Turkish, the Deitels' texts have earned international recognition. Dr. Deitel has delivered hundreds of professional seminars to major corporations, academic institutions, government organizations and the military.

Paul J. Deitel, CEO and Chief Technical Officer of Deitel & Associates, Inc., is a graduate of the MIT's Sloan School of Management, where he studied Information Technology. Through Deitel & Associates, Inc., he has delivered Java, C, C++, Internet and World Wide Web courses to industry clients, including IBM, Sun Microsystems, Dell, Lucent Technologies, Fidelity, NASA at the Kennedy Space Center, the National Severe Storm Laboratory, Compaq, White Sands Missile Range, Rogue Wave Software, Boeing, Stratus, Cambridge Technology Partners, Open Environment Corporation, One Wave, Hyperion Software, Adra Systems, Entergy, CableData Systems and many other organizations. Paul is one of the most experienced Java corporate trainers having taught about 100 professional Java training courses. He has also lectured on C++ and Java for the Boston Chapter of the Association for Computing Machinery. He and his father, Dr. Harvey M. Deitel, are the world's best-selling Computer Science textbook authors.