• Standalone programs
• Run from command line
• Console- or graphic- (window) based

• Program running in the context of a Web page
• Executed (as a client) within a browser

			javac HelloWorld.java
		

• javac is the compiler
• Note the .java extension must be specified
• A .class file is created (in this case HelloWorld.class-- it's the name of the class followed by the .class extension).

			java HelloWorld
		

• java is the interpreter
• The argument os the name of the class-- the .class extension is not specified.

• In general, use the same name for the source file as for its contained class
• Note the main method (function)
  • This is the entry point for the application
  • All Java applications must have a main method
  • The class passed as the argument to the Java interpreter must have a main method
  • System.out is the standard output (console)
  • The array of String parameter to main contain the command-line arguments

			javac HelloWorldApplet.java
		

• Applets run in the context of a Web page, so ...
• ... we need an HTML file that constructs a Web page containing the applet
• A sample HTML file for our applet
• The java interpreter executes standalone applications
• To execute the applet, we need to view the Web page
  • Either in a browser, or
  • From the command-line run the appletviewer utility that comes with the JDK

    	appletviewer HelloWorldApplet.html
    

• Publishing Your Applet
  • If you have a Web site/page, you can place the <applet> tag in the HTML page
  • Otherwise,
    • Go to the atrium, get your Unix account information
    • Login and create a directory public_html
    • Place the .html file and the applet's .class file in the public_html
    • The applet can now be viewed via the URL

      		http://acc4.its.brooklyn.cuny.edu/~your userid/HelloWorldApplet.html
      

      • or acc6, or acc98
• Items to note
  • No main method-- invoked from within an already running program (browser or appletviewer)
  • The applet is a guest of its Web page, therefore its size is dictated by the Web page (i.e., the HTML file
  • The paint method (function) is called when the applet needs to be displayed (painted). We'll talk in greater detail later about this and the Graphic parameter
  • We will talk later about the extends keyword-- for the moment, suffice it to say that HelloWorldApplet is inherited from the Applet class.