Abstract:
Java is a programming language designed primarily for use on the internet. A Java application, called an applet, can be included in an HTML page much like an image. When a Java-compatible browser is used to view the page, the applet’s code is transferred to the system and executed by the browser. Current versions of Netscape and Internet Explorer for Macintosh and IBM computers, and several other platforms, support Java.
Java addresses shortcomings of HTML such as the difficulty of implementing complex interactions between computer and user. Implementing even a simple series of interactions, such as a tic-tac-toe game, would be a daunting task with HTML. With Java, however, the game may be reduced to a few lines of instruction. Implementing an interactive CAI lesson on the internet in which the computer also keeps score would again be a daunting task with HTML. Java handles the task with ease.
Topics presented include the following: an introduction to Java, a look at Java sites on the internet, using existing instructional Java applets in the classroom and in web sites, creating custom Java applets, security concerns, and system requirements.
Introduction
Java was created in 1991 by Sun Microsystems, initially for use as an operating system for consumer devices such as televisions and VCRs. The real growth and popularity of Java, however, occurred when the focus of development shifted to the internet. The most commonly used internet browsers (Netscape Navigator and Internet Explorer) can load and execute Java applets. The execution of the applets is handled by the browser rather than the computer's operating system so Java applets may run on any computer platform (Macintosh, IBM, UNIX, etc.). Those without a Java-capable browser may also run applets by using Sun Microsystem’s Applet Viewer, available for most computer platforms. Java’s cross-platform portability is a feature that appeals to many developers. Java will soon be incorporated in the operating systems of most computers so its popularity should continue to grow.
Java's Future
Numerous computer companies have announced plans to embed Java into their operating systems. These companies include Apple, IBM, Microsoft, Hewlett-Packard, Hitachi, Novell, SiliconGraphics, SunSoft, and others.
A Look at Java Sites on the Internet
Java is in its infancy as a programming language, but music applets are already beginning to appear. Below are descriptions and addresses of pages that present musical concepts. Topics addressed include listening and moving to music, notating and composing music, analyzing and identifying music, and twentieth century compositional techniques.
Also available are applets that can be used to illustrate the connections between music and the visual arts. The Impressionist site (http://reality.sgi.com/grafica/impression/) allows users to convert electronic photographs into Impressionistic style "paintings". These creations contain many of the subtleties, and nuances of music of the age. The Mondrian Creator site (http://pobox.com/~piran/mondrian/creator.html) creates "paintings" in the style of Pier Mondrian, a twentieth-century painter whose rectangular shapes and lines capture the spirit of much twentieth-century music.
Table 1. Selected Music Sites
|
Java Music Box A growing number of applets are used to organize and play musical excerpts. |
http://www-a2k.is.tokushima-u.ac.jp/java/MusicBox.html |
|
Java Keyboard Applet Play tunes by clicking on the keyboard |
http://www.pageplus.com/~bigears/keyboard.html |
|
Ear Training on the Internet Practice interval identification on the internet |
http://www.pageplus.com/~bigears/index.html |
|
Rainer Typke: Tune Recognition Save a monophonic wave file (or write the tune in "contour code") and the computer will guess what it is. Java security prohibits reading local files when run over the internet. |
http://wwwipd.ira.uka.de/tuneserver/ |
|
Java-Dance Refresh your memory of ballroom and popular dances. Animations show where both partners should place their feet for waltzes, foxtrots, etc. |
http://tech-www.informatik.uni-hamburg.de/dance/JDance-e.html |
|
TwelveToneToyBox Create, edit, and listen to twelve tone rows. Calculate matrices instantly. Graphically display the results on a clock face. |
http://www-personal.umich.edu/~fields/TTTB |
|
Musical Set Theory Calculator Create, edit, and hear all types of pitch class sets. |
http://php.indiana.edu/~ltomlin/settheory/ |
|
The vOICe Sonification Applet Create polyphonic compositions by turning notes on and off on a grid. Art may be imported to the grid for interesting results. |
http://ourworld.compuserve.com/homepages/Peter_Meijer/javoice.htm |
|
JComposer Competition for Finale, Encore, and Nightingale is looming. This program takes the initial step toward implementing notation software for the internet. |
http://www.alulabs.com/projects/JComposer |
Educational applets in a number of disciplines are becoming popular. Some distinguished sites are provided in Table 2.
Table 2. Selected Education Sites
|
Math Education Puzzles |
http://mars.superlink.net/abogom/ |
|
Real-Time Satellite Ocean Imagery |
http://narwhal.gso.uri.edu/cwatch1.html |
|
Virtual Science - Basic Scientific Principles |
http://www.dsuper.net/~ashabah/ |
|
College Physics for Biology and Chemistry |
http://www.rwc.uc.edu/koehler/biophys/text.html |
|
Educational Physics Simulations |
http://ucsub.colorado.edu/~gleason/Home.html |
|
Crossword Puzzles - Vocabulary Development |
http://www.puzzledepot.com/java/czplayer.shtml |
|
Weather Visualizer - Satellite/Radar Maps |
http://covis.atmos.uiuc.edu/java/image.html |
One of the most useful features of Java is the level of interactivity that it allows. Table 3 contains links to "arcade" games that illustrate the interactive strengths of Java.
Table 3. Java Games–Java has Significant Interactive Potential
|
- Yahoo Tetris List http://www.yahoo.com/Recreation/Games/Computer_Games/Genres/Strategy/Titles/Tetris/ Interactive_Web_Games/Java/ - Yahoo Space Invaders List http://www.yahoo.com/Recreation/Games/Video_Games/Classic_Arcade_Games/Titles/ Space_Invaders/Java/ - Yahoo Asteriods List http://www.yahoo.com/Recreation/Games/Video_Games/Classic_Arcade_Games/Titles/ Asteroids/Java/ - Yahoo Pong List http://www.yahoo.com/Recreation/Games/Video_Games/Classic_Arcade_Games/Titles/ Pong/Java/ - Solitaire http://www.cogapp.demon.co.uk/piran/patience/ |
The best source of information about Java is its creator, Sun Microsystems. The Java Development Kit, Sun’s "official" documentation, and links to other sites of interest are found at Sun’s internet site (see Table 4).
Table 4. Sun Microsystems Java Sites
|
Sun Microsystems |
http://java.sun.com/ |
|
Java Development Kit |
http://java.sun.com/products/jdk/1.0.2/installation.html |
|
Java API Documentation |
http://java.sun.com/docs/api_documentation.html |
A number of additional sites also disseminate information about Java. Table 5 contains some of the most useful sites.
Table 5. Other Java Sites of Interest
|
Applets from JavaSoft |
http://java.sun.com/applets/js-applets.html |
|
Gamelan |
http://www.gamelan.com/ |
|
Yahoo Java Links |
http://www.yahoo.com/Computers_and_Internet/Programming_Languages/Java/ |
|
JavaWorld |
http://www.javaworld.com/javaworld/common/jw-jumps.html |
|
Netscape’s Selected Java Applets |
http://www.netscape.com/comprod/products/navigator/version_2.0/java_applets/index.html |
|
A Java Tutorial |
http://www.javasoft.com/nav/read/Tutorial/Index.html |
|
Welcome to AppleJava |
http://applejava.apple.com/index.html |
Creating Java Applets
Java applets are written using any text editor or Java authoring tool. They are then compiled into "byte-code" class files using Sun Microsystems Java Development Kit (JDK) or a similar Java development tool. After testing and debugging, applet class files are copied to an internet server (just as any other internet file) and referenced by the html pages.
Security Concerns
Due to the fact that Java applets are widely distributed over the internet, Sun has built security features into them. When loaded from the internet using a browser such as Netscape, applets are not permitted to read or write files locally. They may read or write information to the host computer on which they reside. If an applet is viewed using Sun’s Applet Viewer or compiled into a stand-alone application, they have greater input and output privileges. The chart below summarizes what applets can and cannot do. Notice the strong restrictions in the left-most column of the following chart.
A recently added feature of applets is a signature. Unsigned applets are always restricted, but users may choose to extend greater liberty to known applets.
|
What Applets Can and Cannot Do* |
|||||
|
Stricter –––––––––––––––––-–––––> Less strict |
|||||
|
NN |
NL |
AN |
AL |
JS |
|
|
Read File In /home/me, acl.read=null |
No |
No |
No |
Yes |
Yes |
|
Read File In /home/me, acl.read=/home/me |
No |
No |
Yes |
Yes |
Yes |
|
Write File In /tmp, acl.write=null |
No |
No |
No |
Yes |
Yes |
|
Write File In /tmp, acl.write=/tmp |
No |
No |
Yes |
Yes |
Yes |
|
Get File Info, acl.read=null acl.write=null |
No |
No |
No |
Yes |
Yes |
|
Get File Info, acl.read=/home/me acl.write=/tmp |
No |
No |
Yes |
Yes |
Yes |
|
Delete File, Using File.Delete() |
No |
No |
No |
No |
Yes |
|
Delete File, Using exec /usr/bin/rm |
No |
No |
No |
Yes |
Yes |
|
Read the User.Name Property |
No |
Yes |
No |
Yes |
Yes |
|
Connect to Port on Client |
No |
Yes |
No |
Yes |
Yes |
|
Connect to Port on 3rd Host |
No |
Yes |
No |
Yes |
Yes |
|
Load Library |
No |
Yes |
No |
Yes |
Yes |
|
Exit(-1) |
No |
No |
No |
Yes |
Yes |
|
Create a Popup Window Without Warning |
No |
Yes |
No |
Yes |
Yes |
|
Key: •NN: Netscape Navigator 2.x, loading applets over the Net •NL: Netscape Navigator 2.x, loading applets from the Local file system •AN: Appletviewer, JDK 1.x, loading applets over the Net •AL: Appletviewer, JDK 1.x, loading applets from the Local file system •JS: Java Standalone applications |
|||||
*This table was created using information from Sun Microsystem’s internet site. An extensive discussion of security issues is available at the site (http://java.sun.com).
Suggested Reading
The first place to turn for information on Java is the Sun Microsystems site on the internet. Complete API documentation and links to several on-line tutorials are available. Documentation and tutorials may also be downloaded.
Sun Microsystems http://java.sun.com/
Java Development Kit http://java.sun.com/products/jdk/1.0.2/installation.html
Java API Documentation http://java.sun.com/docs/api_documentation.html
A Java Tutorial http://www.javasoft.com/nav/read/Tutorial/Index.html
Selected Java Bibliography
The following list of books was found on America On-Line’s Java forum.
IDG Books (800-762-2974)
Creating Cool Web Applets with Java
Danny Goodman's JavaScript Handbook
Foundations to Java Programming for the World Wide Web
Osborne/McGraw-Hill (800-227-0900)
The Java Handbook
Que Books (800-428-5331)
Learn Java in 7 Days
The Coriolis Group Inc (800-410-0192)
Java Programming EXplorer (book/CDROM)
The Java Programming Language
O'Reilly & Associates (800-998-9938)
Java Explorer
Java in a Nutshell: Quick Reference for Desktop Java Programmers