Newbie: -classpath option of java does not load the content of the jar file

I have the following command:
java j -classpath ojdbc14.jar

The file "ojdbc14.jar" is in my current directory. If I use the
verbose mode, I can see that the odbc package is not getting loaded.

If I un-jar the content of ojdbc14.jar in my current directory and run
in verbose mode, I can see it is being loaded:

Start...
[Loaded java.lang.Package from C:\Program Files\Java\jre1.5.0_10\lib
\rt.jar]
[Loaded java.sql.Driver from C:\Program Files\Java\jre1.5.0_10\lib
\rt.jar]
[Loaded oracle.jdbc.driver.OracleDriver from file:/C:/_t/Java/

Why do I need to un-jar the package ?

Thanks

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