Thursday, January 24, 2001

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CM245 Lecture 2
CM245 - Contemporary Programming Methods Lecture 2
Thursday, January 24, 2001 Cecil P.
Schmidt Department of Computer Information
Sciences Washburn University Topeka, KS.
66621 zzschmid_at_washburn.edu
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Presentation Outline

• Files and Directores
• Building a java program
• Applets versus applications

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Files and Directories

• Java source file ltfilename.javagt
• Java object file ltfilename.classgt
• Typical data file ltfilename.datagt
• Directory contains a set of (related) files

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How Do You Build a Java Program

• Text Editor with Java Development Kit (JDK)
• Integrated Development Environments (IDE)
• VisualAge Java
• Visual J
• JBuilder
• An IDE is great for large applications, screen
  painting and debugging. Its best to learn
  without one first.
• We are not using an IDE for this class. We are
  using the text editor option.

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Applets vs. Applications (Review)

• Applets are invoked as part of a Web page
• Applets cannot run alone. The must run with the
  aid of a browser.
• Applications are free standing programs
• Applications require the main method
• example Hello.java

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Hello.java Application

• /
• File Name Hello.java
• Author Cecil Schmidt
• Date Written 06/06/2001
• Description This program is used to
  illustrate a simple stand alone version
• of a Java program.
• /
• import java.io. //We are importing a library of
  classes to do I/O.
• //The class name "Hello" must be the same name as
  the file name on disk
• //except that the file name must end in ".java".
  For example, the physical
• //file name of this program is "Hello.java" and
  the class name is "Hello".
• public class Hello
• //The main method is required in all stand
  alone programs.
• public static void main(String args) throws
  IOException
• System.out.println("Hello CM245 Class!")
• //System is an object you get for "free". It
  allows you to

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Edit-Compile-Execute Process

• Edit build a .java file using either an IDE or
  an editor
• Compile converts .java to .class (byte code)
• Execute run the .class file with the JVM

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Creating and running an applet

• HelloApplet.java
• Using the appletviewer utility
• Setting your display variable
• Moving the file to your web site after testing

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HelloApplet.java

• /
• File Name HelloApplet.java
• Author Cecil Schmidt
• Date Written 06/07/2001
• Description
• This program is used to illustrate a simple
  applet.
• /
• import java.awt. //Abstract Windowing Toolkit
• import java.applet.Applet
• public class HelloApplet extends Applet
• //The paint method is required in all
  applets.
• public void paint(Graphics g)
• //draw text on graphic obect.
• g.drawString("Hello CM245 Class!", 50, 50)

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HelloApplet.html

• lthtmlgt
• ltheadgt
• lttitlegtHello Appletlt/titlegt
• lt/headgt
• ltbodygt
• ltapplet codeHelloApplet.class width300
  height200gt
• lt/appletgt
• lt/bodygt
• lt/htmlgt