Using a CSV Parser class

Question

Ok so I've been wrestling with the issue of CLASSPATH and packages for the last week or so, and I'm truely, completely fed up. Maybe there's a kind soul to show me my mistake?
Here's the code
import java.io.*;
import com.Ostermiller.util.*;
public class Extractor {
     public static void main ( String args[] )
          // Create the printer
          ExcelCSVPrinter ecsvp = new ExcelCSVPrinter( System.out );
          // Write to the printer
          try {
               ecsvp.writeln( new String[]{"hello","world"} );
          } catch (IOException iox){
               System.out.println("IO error");
} So, I'm importing the java packages and the Ostermiller utils. I simply create a ExcelCSVPrinter instance and I tell it to write out the string array Hello World.
Now this compiles fines, using javac -cp c:\docume~1\britt\mydocu~1\ostermillerutils_1_04_03.jar Extractor.java
But when it try to java Extractor, I get the classic "NoClassDefFound Extractor" error. Even, if I include the same classpath which works for compiling, it still is a no-go.
I have the feeling this is a very basic mistake I'm making here, but I just can't see it.

Answer 1

The files in the jar are inside a package. The correct (and only) way to address these files is to use the full name, i.e.,
com/Ostermiller/util/Extract
Here's some information about packages. This is a minimal explanation.
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)