Java EE (Java Enterprise Edition) General Discussion

Hi Guys,
I am trying to run a webserivce from Eclipse 3.4 with webservice explorer on Tomact 6.0 server. Just i created a java class which contains one method which takes input parameter as a String and returns a string. With Apache Axis generated a client program .But when i run my webservice by giving a input string in WS explorer , the Soap request is generated and SOAP response which it returns is :

<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<soapenv:Fault>
<faultcode>soapenv:Server.userException
</faultcode>
<faultstring>java.lang.InstantiationException:
com.test.FirstTest</faultstring>
<detail>
<ns1:hostname xmlns:ns1="http://xml.apache.org/axis/">BGHWF9873
</ns1:hostname>
</detail>
</soapenv:Fault>
</soapenv:Body>
</soapenv:Envelope>

SOAP response contains <faultcode>soapenv:Server.userException & <faultstring>java.lang.InstantiationException.
Can anybody explains me why SOAP response contains faultcode and faultstring. How can be it resloved?????

Thanks,
Ram.