How one can manage this kind of error in java:
exception in thread main java.lang.noclassdeffounderror gnu/io/commportidentifier?

I'm running a program (which is built to move a robot arm) after I compiled my program ( I've already installed the rxtx and those stuff) , and tried to run it I got error like this:
Exception in thread "main" java.lang.NoClassDefFoundError: javax/comm/CommPortIdentifier
                        at ComPort.identify(ComPort.java:14)
                        at ComPort.main(ComPort.java:9)
Caused by:   java.lang.ClassNotFoundException: javax.comm.CommPortIdentifier
                       at java.net.URLClassLoader$1.run(Unknown Source)
                       at java.net.URLClassLoader$1.run(Unknown Source)
                       at java.security.AccessController.doPrivileged(Native Method)
                       at java.net.URLClassLoader.findClass(Unknown Source)
                       at java.lang.ClassLoader.loadClass(Unknown Source)
                       at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
                      at java.lang.ClassLoader.loadClass(Unknown Source)
                       ... 2 more




2014-08-26/21:04:39