Starting A Java Program - Let Me Count The Ways
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Java programs can be started a number of ways. Here are two we use in this course:
1. Standalone Java Programs
2. Java Applets
Standalone Java Program
A standalone Java program starts from a version of the Java Virtual Machine designed to run from the operating system. With a standalone Java program, you can program most anything you want. Starting Java as a standalone program is what we will use most of in the course. A standalone program can output to a console window in a text format. For Windows this is the command prompt window. A standalone program can also launch GUI (Graphical User Interface) windows.
 
Java Applet
An applet starts from a version of the Java Virtual Machine designed to run inside a web browser. Applets are limited to what is allowed in a Web Browser. For example you are not allowed to tamper with the computer's operating system, hard drive, etc. without a security ok from the owner. Starting Java as an applet we do in the last week of the course. The Java Software Development Kit comes with an Appletviewer program that lets you test applets. With the Appletviewer on in a web browser you also can display text formatted output to a console window.
 
Java on Web Servers
Java also runs from web servers. Web server software is required to provide the interface to the Java Virtual Machine for this.
 
One example is Java Server Pages (JSP). JSP allows you to place Java code inside a web page so that the web server can process it before responding to a web request. For example the JSP code may look up a search request in a database and form the remaining part of the web page's HTML (HyperText Markup Language).