How To Handling Packages with the Visual J++ Compiler


When the Visual J++ compiler, Jvc.exe, sees a package statement, it
automatically creates the directory structure needed for the package
declared. The .class files that define the classes in the package must be
placed in this directory structure. By default, they are not placed in the
correct directory. You must specify an output directory to tell the
compiler where to place the .class files.


The .class files that define the classes in a package must be placed in a
directory that matches the package name. For example if you were to define
a package called "animals.dogs," the .class files that define the classes
in this package must be located in the "animals\dogs" directory.

In order for the compiler to place the .class files in the correct
directory, you must specify an output directory by clicking Settings on the
Build menu. The Project Settings dialog box appears. Click the General tab
if it is not already selected.

You will see two edit boxes, the second of which is labeled "Output
Directory." The directory entered here is used as the root of the directory
structure created for a package. If using the command line, Jvc.exe has a
"/d" command line switch that lets you specify the output directory. You
can also use a "." as the output directory and the compiler creates the
necessary directories under the current structure and places the .class
files there.

Thus if you entered c:\msdev\projects\packtest for the output directory,
and you compiled a .class file with the package statement above, the
following directory is created:

The resulting class files are placed in this directory.

When compiling a class file that imports a package, the compiler searches
the directories in the classpath for a directory that matches the name of
the imported package. It then looks in that directory for the class files
that define the class. If the class file cannot be found, the compiler
gives J0049 (Undefined Name) and J0044 (Cannot find definition for class)

Note that only the top-most directory in a package directory structure must
be in a directory that's listed in the classpath. Continuing on with the
animals.dogs sample, only the directory that contains the animals directory
must be listed in the classpath (that is, c:\msdev\projects\packtest must
be in the classpath). Once the compiler finds the animals directory it
knows how to find the .class files in the subdirectories of animals. When
searching for directories, Microsoft Developer's Studio (MSDEV) makes sure
that the current project directory appears in the classpath.

When running an application or an applet, the Microsoft virtual machine
similarly searches the classpath for the needed .class files.
Since the root directory of the package hierarchy must be in the classpath,
it's a good idea to have a central location for all packages. When you
installed Visual J++, one was created for you:

This directory is automatically included in the classpath. If you choose
not to use a central repository, each time you create a package, you must
add an additional entry to your classpath.


For the latest Knowledge Base articles and other support information on
Visual J++ and the SDK for Java, see the following pages on the Microsoft
Technical Support site:


Id. de artículo: 162129 - Última revisión: 02/14/2017 - Revisión: 1

Microsoft Visual J++ 1.0 Standard Edition, Microsoft Visual J++ 1.1 Standard Edition