Java Database Connectivity (JDBC)

Hello,
I trie to install openexchange on my debian system. Now I have problems getting the postgresql jdbc driver working with java. I use the following versions:

java -version
java version "1.5.0_08"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_08-b03)
Java HotSpot(TM) Client VM (build 1.5.0_08-b03, mixed mode, sharing)


psql --version
psql (PostgreSQL) 7.4.7

pg74.216.jdbc3.jar


I am using the following code to test if the driver works:

############## Example1.java #############################

import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.SQLException;

public class Example1 {
public static void main(String[] argv) {
System.out.println("Checking if Driver is registered with DriverManager.");

try {
Class.forName("org.postgresql.Driver");
} catch (ClassNotFoundException cnfe) {
System.out.println("Couldn't find the driver!");
System.out.println("Let's print a stack trace, and exit.");
cnfe.printStackTrace();
System.exit(1);
}

System.out.println("Registered the driver ok, so let's make a connection.");

Connection c = null;

try {
// The second and third arguments are the username and password,
// respectively. They should be whatever is necessary to connect
// to the database.
c = DriverManager.getConnection("jdbc:postgresql://localhost/booktown",
"username", "password");
} catch (SQLException se) {
System.out.println("Couldn't connect: print out a stack trace and exit.");
se.printStackTrace();
System.exit(1);
}

if (c != null)
System.out.println("Hooray! We connected to the database!");
else
System.out.println("We should never get here.");
}
}
##############################################################

If I type: java Example1
I get:
Exception in thread "main" java.lang.NoClassDefFoundError: Example1

It has nothing to do with the CLASSPATH because if I set CLASSPATH to nothing I get:

java Example1
Checking if Driver is registered with DriverManager.
Couldn't find the driver!
Let's print a stack trace, and exit.
java.lang.ClassNotFoundException: org.postgresql.Driver
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:164)
at Example1.main(Example1.java:10)

It seems like there is something not working correctly. But what??? I tried now every jdbc driver of postgresql - every time the same error. Any idears?

Thanks,
Joachim