Introduction to Java Applets

1
Introduction to Java Applets

• Understanding Applets
• Editing, and Running Applets

2
Introduction

• Why Java?
• current
• portable
• Applets and Applications

3
Why Object-Oriented Programming?

• Encapsulation (modeling)
• keeps data and its behavior together
• allows to create models (classes)
• Inheritance (reusability)
• allows to reuse code
• Java API

4
Reading an Applet

• In Java we can create Applications or Applets
• Applet is a Java program designed to be run by a
  web browser or applet viewer
• Application is a stand alone Java program which
  runs from the console window

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Java Applets

• Provide user interface (GUIs)
• More than just banners, logos, and picts
• They need a browser to run
• Machine independent

6
Components of an applet

• Comments
• Import statements
• packages
• classes
• Class Definition
• public
• private, protected
• class
• Hello
• extends Applet
• inheritance

7
Components of an applet - cont.

• Body of the class
• Methods and Methods Definitions
• data
• methods
• public void paint(Graphics g)
• g.drawString(Hello, 30 , 30)
• calling a method
• parameters
• g.drawRectangle(20, 5, 140, 50)

8
Running an Applet

• Using CodeWarrior
• Save the source file (.java) with the same name
  as the name of the class.
• Then, edit the TrivialApplet.html file
• Make sure to change the name of the .class file
  under code
• The name of your source file the name of the
  Java class are important. They both should have
  the same name!

9
Finding and Fixing Errors

• Syntax errors
• execution (logical) errors
• BE PATIENT!
• IMPLEMENT AND TEST!

10
A second look at Applets

• Keywords
• Look up a list of all Java reserved words
• Identifiers
• Look up Java naming conventions
• Statements
• semicolons
• Applet Window
• dimensions
• Java Graphics Class
• Look up a brief description of this class

11
Graphics in Java

• The AWT includes a Graphics Class
• What does AWT mean?
• http//java.sun.com/j2se/1.4/docs/api/index.html/
• live by this site!

12
Homework

• readings
• Chapter 2
• Start thinking about Lab02 due Sunday Sept. 11th
• Lab01 is due Thursday by 800am
• Check Exercise-01.doc