Help Required on WDK Preconditions

Hello Experts,

I am new to WDK. I managed to create a custom menu item with the help of WDK Tutorial.
Now I trying to make a menu Item visible only when the selected document is checked out. I am trying to do this preconditions.
However, I am getting Error below error from the prevalidation class when logging into webtop. I am unable to fix it. Can someone please help?

Error

Action Service - unable to instantiate qualifier class: com.ford.custom.PrivilegedCancelCheckoutPreCondition
class java.lang.InstantiationException

==========================================================================

My Action XML
=====================

<config version = "1.0">
<scope type="dm_sysobject">
<action id = "privileged_cancel_checkout_action">

<params>
    <param name="objectId" required="true"/>
<param name="lockOwner" required="true"/>
    </params>

<preconditions>
<precondition class="com.ford.custom.PrivilegedCancelCheckoutPreCondition">
</precondition>
</preconditions>

<execution class="com.documentum.web.formext.action.LaunchComponent">

<component>privileged_cancel_checkout_component</component>
   
<container>dialogcontainer</container>
</execution>
</action>
</scope>
</config>

===================================================================
My PreCondition Class:
public abstract class PrivilegedCancelCheckoutPreCondition implements IActionPrecondition

{
final private static String m_strRequiredParams[] = new String[] {"objectId", "lockOwner"};
String[] getRequiredParams()
{
  System.out.println("************ INto the getRequiredParams...");
  return m_strRequiredParams;
}

public boolean queryExecute(String strAction, IConfigElement config, ArgumentList arg, Context context, Component component)
{
  boolean execute = false;
  try
  {
   //get object ID  
   String objId = arg.get("objectId");
   String strLockOwner = arg.get("lockOwner");  
   if ( strLockOwner == null || strLockOwner.length() == 0 )
    { 
    execute = true; 
    }  
  }
  catch(Exception de)
  {
   execute = false;
  }
  return execute;  
  }

}
==========================================================================

Best Regards,

A