Spicing Up Your Site with Java Applets in Java

Paint Code 128 Code Set C in Java Spicing Up Your Site with Java Applets

Can t find a Java applet on the Web that does exactly what you want it to do You can create your own Java applet! Creating your own Java applets is relatively difficult (unless you happen to be a computer programmer), but it s not impossible Due to space constraints, in this section I give you an overview of how to go about programming in Java just enough to whet your appetite For more in-depth information, two other books can give you the complete story: See Beginning Programming with Java For Dummies or Java 2 For Dummies, both by Barry Burd (published by Wiley Publishing, Inc)

If you have a Web browser such as Netscape Navigator or Microsoft Internet Explorer installed on your computer, you can execute Java applets; that s because a Java execution environment called the Java virtual machine, or JVM, is built into Netscape Navigator, and you can download and add thirdparty JVMs, such as the one available from Sun Microsystems, to Internet Explorer

One of the characteristics for which Java is often lauded is its ability to run unchanged on computers ranging from tiny handhelds to massive supercomputers in other words, its portability (Portability is often referred to as cross-platform capability, because portable code can execute on, or across, many different hardware/software platforms) Although Java does strive to be a portable language in theory, it often falls short in practice Here s why Java compilers and interpreters do their best to translate Java source code into bytecode, and bytecode into machine code, respectively But how they do this translation is dependent on at least a couple of variables: The target platform: IBM personal computers, Sun workstations, and Macintosh notebooks are different period As in human languages, some things just don t translate So if you re trying to accomplish a task using Java that the underlying operating system on one computer just can t handle, what language you re developing in doesn t matter; you re out of luck The developers creating the compilers and interpreters: Different companies create and distribute different Java compilers and interpreters Sun established a Java standard and makes that standard available to any companies who want to license it Human nature being what it is, however, the end result intentional or not is that differences exist between Java compilers and runtime implementations The upshot Whereas creating cross-platform programs using Java is easier than probably any other language out there, it s not a given In other words, programming in Java doesn t guarantee portability; it just makes creating portable programs easier

Before you can create Java programs of your own, however, you need more than just a Java-supporting browser You need to have the following software installed on your computer: A copy of the Java development kit: The Java SDK (which stands for Software Development Kit) contains all of the following: The Java class libraries (prebuilt Java classes, or APIs) and language support you need to create Java applets The compiler (called javac) you need to turn Java source files into bytecode A Java runtime environment (called appletviewer) you use to turn compiled bytecode into machine language in other words, to test the applet

You can download a free copy of the Java 2 SDK, standard edition (the latest Java development kit at the time of this writing) from javasun com/j2se A text or graphical editor: All Java programs begin as Java source code, which is plain text you save using the java file extension So, before you can create a Java program, you need to have a text editor installed on your machine Depending on your preference, you can use a plain text editor (such as the Notepad application that comes bundled with Windows), a text editor designed specifically for programmers (such as TextPad), or an integrated development environment (IDE) designed specially for Java programmers IDEs (such as Borland s JBuilder and Sun s ONE Studio) combine a graphical, drag-and-drop editor with built-in code snippets, a Java compiler, and a code checker Java IDEs help you create Java applets much more quickly than you can by typing Java code into a text editor and compiling that code into executable applet form