Java Quick

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JavaQuick Dirty

• By Bert Wachsmuth

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Overview

• We will cover
• What is Java
• Using and Writing Java applets
• Getting more information
• We will need
• Knowledge of HTML and web page creation
• We will get
• Basic understanding of Java but we willNOT
  become the worlds foremost Java programmer

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What isJava

• Java is a programming language that
• Is exclusively object oriented
• Has full GUI support
• Has full network support
• Is platform independent
• Executes stand-alone or on-demand in web
  browser as applets

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Simple Example
Web page with Java applet
HTML code for above web page
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Simple Example
Java code for TickerApplet
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Example Summary

• To create a web page with an Applet you need
• A Java-aware web browser (usually beyond your
  control)
• A web page including a special HTML tag called
  ltAPPLETgt tag
• One or more Java class files (produced separately
  from Java source code)

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Using JavaApplets

• To use Java applets, you
• Locate appropriate class file(s)
• Learn how to configure applet
• Embed the Applet into web page
• ltapplet codebasebase_url // if different
  from current directory
• codeAppletName.class // name of class
  file
• width // width of
  applet area
• heightgt // height of
  applet area
• lt/appletgt // do not forget
  this

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Simple Applets

• TickerTape
• codebase http//pirate.shu.edu/wachsmut/Ticker
  code TickerApplet.classwidth 300, height30
• 3D Surface
• codebase http//pirate.shu.edu/wachsmut/Surface
  code surface.classwidth 500, height550
• Missile Defense
• codebase http//www.csd.uu.se/d95vil/missile/cl
  assescode MissileCommand.classwidth 320,
  height 200

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Configurable Applets

• Many applets can be configured using param
  tags
• Inquire about name and meaning of param tags
  for the applet
• Add param tags to HTML as needed
• ltapplet codebasebase_url
  codeAppletName.class
• width
• heightgt ltparam nameName
  valueValuegt ltparam nameName2
  valueValue2gt ...lt/appletgt

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Configurable Applet Examples

• TickerTape
• codebase http//pirate.shu.edu/wachsmut/Ticker
  code TickerApplet.classwidth 300,
  height30param msg, delay, foreground,
  background
• Chatterbox
• codebase http//sciris.shu.edu/Java/Chatcode
  ChatterBoxlet.classwidth 200, height50param
  host (use sciris.shu.edu), port (use 1234)
• Note Applets can be embedded easily with
  FrontPage or Notes (LearningSpace)

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WritingJava Applets

• To create Java Applets, you need
• Knowledge and a good Java book
• Good ideas, patience, and persistence
• and
• A text editor Java compiler
• or
• An Integrated Developing Environment (IDE)

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Tools for WritingJava Applets

• Java API -gt essential resource
• http//mathcs.shu.edu/Resources/Java/API/
• Editor -gtProgrammers File Editor
• http//www.lancs.ac.uk/people/cpaap/pfe/
• Compiler -gt SUNs Java compiler
• http//www.javasoft.com/
• IDE -gt BlueJ version 1.1
• http//bluej.monash.edu/
• IDE -gt Microsoft Visual J 6.0
• Available from SHU but not recommended

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Writing Applets - Intro

• Java Applets are saved as Name.java
• They must be compiled into Name.class
• They require HTML page to run
• They have fields and methods
• fields are used to store data
• methods are used to perform action
• They inherit lots of fields and methods from
  parent classes

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Writing Applets - Framework

• import java.awt.
• import java.awt.event.
• import java.applet.Applet
• public class Name extends Applet implement
  ActionListener
• private type aField new type(foo)
• public void init()
• / code here when applet is initialized /
• public void start()
• / code here to execute when page is visited
  /
• public void stop()
• / code here to execute when page is left /
  
• public void paint(Graphics g)
• / drawing code goes here /
• public void actionPerformed(ActionEvent ae)
• / code to react to action events here /

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Writing Applets Example 1
Steps

• Open editor
• Type this source code
• Save as Junk.java
• Compile into Junk.class
• Create HTML document
• Add proper ltappletgt tag
• View in web browser

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Writing Applets Example 2
Steps

• Need two pictures namedpicture1.jpg and
  picture2.jpg
• Open editor
• Type this source code
• Save as Slide.java
• Compile into SSlide.class
• Create HTML document
• Add proper ltappletgt tag
• View in web browser

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Enhancing Applet 2
Steps

• Modify previous source code
• Save and compile
• Add proper ltparamgt tag(s) to previous HTML
  document
• View new applet in web browser (quit and restart)

Questions

• What parameter tag(s) to use?
• What must image names be?
• How many images can be loaded?

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Self-runningApplet
Steps

• Modify previous source code
• Save and compile
• View new applet in web browser (quit and restart)

Questions

• Whats happening?
• Whats the delay?
• Pick a new ltparamgt tag!
• Does paint method change?

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A ProfessionalApplet

• To create a professional Applet
• small, fast loading, preloading resources
• completely fool-proof
• completely configurable
• utilizes reusable components (objects)
• cool and new
• Too much for this course

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Whats the Object of Object-Oriented Programming?

• OOP revolves around 6 principles
• Classes Fundamental structure of every Java
  program (fields and methods)
• Objects Are constructed from class blueprints
• Encapsulation Regulate access to class members
• Overloading Multiple definitions for methods
• Inheritance Relationships between classes
• Polymorphism To deal with related classes based
  on common features

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OOP Example

• Our Task
• Create a unit conversion applet that converts
  between feet and meter
• The program should execute in a separate window
• The program should have one menu item to exit

• Steps
• Think about the objects to be used
• Download the files from the web site
• Compile, execute, test, and IMPROVE

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Some less-good News

• Java has version problems with applets
• 1.0 Netscape 3, IE 3
• 1.1 Netscape lt 4.5, IE 4
• 1.2 Netscape gt 4.5, IE 4
• 1.3 Netscape 6 or Java plugin
• Platform independent questionable (lt1.3)
• C native code is faster
• No access to system-level programming
• Large Programs need long download times
• Applets have Security Restrictions (no saving)

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More Information

• Suns Website Online Tutorials
• http//www.javasoft.com/
• JARS Resources
• http//www.jars.com/
• Seton Hall Classes
• CSAS1111, CSAS1112, etc
• Java by Definition
• http//pirate.shu.edu/wachsmut/jbd/
• Books
• See Barnes Nobles or Amazon.com

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The End
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What isJavaScript

• JavaScript is a programming language that
• Is object-oriented but loosely typed
• Has no GUI support but supports most web page
  elements
• Is somewhat standardized and runs only inside a
  JavaScript-aware web browser
• Code is embedded directly in a web page
• Is a lot easier than Java
• JavaScript Example
• ltscript languageJavaScriptgt
• document.writeln(Today is (new Date()))
• lt/scriptgt