How scale a Mina client

[Le Van]

Hi all,
I'm very new to Mina. So sorry for my stupid question.
I'm using Mina 2.0.0. RC1. I try Mina by learning example ( SumUp in Mina
example).
I've modified client as following

for(int i=0;i<80;i++) {
     new Thread(new Runnable () {
            ..... // code is same as Client.java
          }
    }.start();

}

Yes, I tried to run simultaneously 80 threads to test how scale a Mina
server is. As a result, I got the error
java.lang.NoClassDefFoundError: Could not initialize
class.sun.nio.ch.FileDispatcher

I don't know the error means. I testes with 70 threads. It works OK

Any help? Thanks.

Van.