2.34 Jb0270: java oop: packages  (Page 5/6)

First, you must create your folder hierarchy to match the package directive that you intend to use. Remember to construct this hierarchydownward relative to the folder specified at the end of your classpath setting. If you have forgotten the critical rule in this respect, go back and review it.

Next, place source code files in each of the folders where you intend for the class files associated with those source code files to reside. (After you have compiled and tested the program, you can remove the source code files if youwish.)

You can compile the source code files individually if you want to, but that isn't necessary.

One of the source code files will contain the controlling class . The controlling class is the class that contains the main method that will be executed when you run the program from the command lineusing the JVM.

Make the directory containing that source code file be the current directory. (If you don't know what the current directory is, go out and get yourself a DOS For Dummies book and read it.)

Each of the source code files must contain a package directive that specifies the package that will contain the compiled versions of allthe class definitions in that source code file. Using the instructions that I am giving you, that package directive will also describe the folder thatcontains the source code file.

Any of the source code files containing code that refers to classes in a different package must also contain the appropriate import directives,or you must use fully-qualified package names to refer to those classes.

Then use the javac program with your favorite options to compile the source code file containing the controlling class. This will cause all ofthe other source code files containing classes that are linked to the code in the controlling class, either directly or indirectly, to be compiledalso. At least an attempt will be made to compile them all. You may experience a few compiler errors if your first attempt at compilation is anything like mine.

Once you eliminate all of the compiler errors, you can test the application by using the java program with your favorite options to execute the controlling class.

Once you are satisfied that everything works properly, you can copy the source code files over to an archive folder and remove them from the packagefolders if you want to do so.

Finally, you can also convert the entire hierarchy of package folders to a jar file if you want to, and distribute it to your client. If youdon't remember how to install it relative to the classpath variable, go back and review that part of the module.

Once you have reached this point, how do you execute the program. I will show you how to execute the program from the command line in the sample program inthe next section. (Actually I will encapsulate command-line commands in a batch file and execute the batch file. That is a good way to guard againsttyping errors.)

Sample program

The concept of packages can get very tedious in a hurry. Let's take a look at a sample program that is designed to pull all ofthis together.