Java™ Application Development on Linux - Dator

5.3 The Java Compiler117NOTEBy the way, you will notice that we do not cover the installation of the <strong>Development</strong>Kit in this chapter. That is because we are deferring the discussion of installationfor the next chapter, where we also introduce the concept of multipleconcurrent <strong>Development</strong> Kits on a single box. See Chapter 6 for details.5.3THE JAVA COMPILERAt the heart of the SDK is javac, the Java compiler. The general form of javacfollows:javac [option...] [sourcefile...] [@optfile...]The option list may be zero or more command-line options. We’ll detailthose later. The sourcefile list may be the name of zero or more Java sourcefiles. Usually you specify just the “main” class of an application. As we will describelater, javac generally will compile all necessary .java files for any classesthat main() class references, directly or indirectly. If you prefix a filename withthe at sign (@), the contents of the file will be treated as if they had been typedon the command line.5.3.1 Compiler Behavior, Defaults, and Environment VariablesIn the simplest case—compiling a single class, such as our FetchURL.javaclass—you get no diagnostics on success (Example 5.1).Example 5.1 Compiling FetchURL.java$ javac FetchURL.java$There will now be a new file, FetchURL.class, in the directory with theJava source file. Let’s run that again with a command-line option we will detaillater (Example 5.2).Boy, our single, simple, one-class application sure uses a lot of classes! Itdoes. Where did they come from? They come from the classes referenced by