Compiling fails of a project with packages

This is a minimal explanation of packages.

Assume that your programs are part of a package named myapp, which is specified by this first line in each source file:

package myapp;

Also assume that directory (C:\java\work\) is listed in the CLASSPATH list of directories.

Also assume that all your source files reside in this directory structure: C:\java\work\myapp\

Then a statement to compile your source file named aProgram.java is:

C:\java\work\>javac myapp\aProgram.java

And a statement to run the program is:

java myapp.aProgram

(This can be issued from any directory, as Java will search for the program, starting the search from the classpath directories.)

Explanation:

Compiling

A class is in a package if there is a package statement at the top of the class.

The source file needs to be in a subdirectory structure. The subdirectory structure must match the package statement. The top subdirectory must be in the classpath directory.

So, you generate a directory structure C:\java\work\myapp\ which is the [classpath directory + the package subdirectory structure], and place aProgram.java in it.

Then from the classpath directory (C:\java\work\) use the command: javac myapp\aProgram.java

Running

-

Compiling creates a file, aProgram.class in the myapp directory.

(The following is where people tend to get lost.)

The correct name now, as far as java is concerned, is the combination of package name and class name: myapp.aProgram (note I omit the .class) If you don't use this name, java will complain that it can't find the class.

To run a class that's NOT part of a package, you use the command: java SomeFile (assuming that SomeFile.class is in a directory that's listed in the classpath)

To run a class that IS part of a package, you use the command java myapp.aProgram (Note that this is analogous to the command for a class not in a package, you just use the fully qualified name)

ChuckBinga at 2007-7-13 1:40:41 >