What is Java?

What is Java?

Java is an object-oriented programming language developed by Sun Microsystem a company best known for its high-end Unix workstations. Modeled after C++, the Java language was designed to be small, simple, and portable across platforms and operating systems, both at the source and at the binary level (more about this later). Java is often mentioned in the same breath as HotJava a World Wide Web browser from Sun like Netscape or Mosaic (see Figure 1.1). What makes HotJava different from most other browsers is that, in addition to all its basic Web features, it can also download and play applets on the reader’s system. Applets appear in a Web page much in the same way as images do, but unlike images, applets are dynamic and interactive. Applets can be used to create animations, figures, or areas that can respond to input from the reader, games, or other interactive effects on the same Web pages among the text and graphics. Although HotJava was the first World Wide Web browser to be able to play Java applets, Java support is rapidly becoming available in other browsers. Netscape 2.0 provides support for Java applets, and other browser developers have also announced support for Java in forthcoming products.

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To create an applet, you write it in the Java language, compile it using a Java compiler, and refer to that applet in your HTML Web pages. You put the resulting HTML and Java files on a Web site much in the same way that you make ordinary HTML and image files available. Then, when someone using the HotJava browser (or other Java-aware browser) views your page with the embedded applet, that browser downloads the applet to the local system and executes it, and then the reader can view and interact with your applet in all its glory (readers using other browsers won’t see anything). You’ll learn more about how applets, browsers, and the World Wide Web work together further on in this book. The important thing to understand about Java is that you can do so much more with it besides create applets. Java was written as a full-fledged programming language in which you can accomplish the same sorts of tasks and solve the same sorts of problems that you can in other programming languages, such as C or C++. HotJava itself, including all the networking, display, and user interface elements, is written in Java.