CPSC1301 Computer Science 1

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CPSC1301Computer Science 1

• Introduction Applets

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Applets

• A Java application is a stand-alone program with
  a main method
• A Java applet is a program that is intended to
  transported over the Web and executed using a web
  browser
• An applet can also be executed using the
  appletviewer tool of the Java Software
  Development Kit (also through most IDEs including
  BlueJ)
• An applet doesn't have a main method Instead,
  there are several special methods that serve
  specific purposes

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Applets

• The class that defines an applet extends the
  Applet class using inheritance
• An applet is embedded into an HTML file using a
  tag that references the bytecode file of the
  applet
• The bytecode version of the program is
  transported across the web and executed by a Java
  interpreter that is part of the browser

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HTML file calling an Applet

• lt!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"gt
• ltHTMLgt
• ltHEADgtltTITLEgtHello World Appletlt/TITLEgtlt/HEADgt
• ltBODYgt
• ltAPPLET CODEHelloWorld.class WIDTH200
  HEIGHT100gt
• ALT "Applet could not be loaded
• Sorry, it is time to upgrade your browser to a
  Java powered one.
• lt/APPLETgt
• lt/BODYgt
• lt/HTMLgt

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Applets

• The paint method is typically used to draw the
  applets contents
• The paint method accepts a parameter that is an
  object of the Graphics class
• A Graphics object defines a graphics context on
  which we can draw shapes and text

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Java Applet

• import java.awt.Graphics
• // Applet that displays Hello World on the screen
• public class HelloWorld extends
  java.applet.Applet
• public void paint(Graphics g)
• g.drawString("Hello World", 5, 50)

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Java Applet

• import java.awt.Graphics
• // Applet that displays Hello World on the screen
• public class HelloWorld extends
  java.applet.Applet
• public void paint(Graphics g)
• g.drawString("Hello World", 5, 50)

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Sample Java Applets

• http//csc.colstate.edu/summers/NOTES/JAVA.HTM
• http//csc.colstate.edu/summers/NOTES/java-example
  s.htm