Thread: What is the Problem With This Code?

I wrote a JavaBean to interface with another third party application but I am having the error below:

Caused by: java.util.NoSuchElementException
at java.util.HashMap$HashIterator.nextEntry(HashMap.j ava:796)
at java.util.HashMap$KeyIterator.next(HashMap.java:82 8)
at voiceexpert.DiagnosingEngine.execute(DiagnosingEng ine.java:33)
at voiceexpert.Symptoms.process(Symptoms.java:57)
... 21 more
I think the problem is in the "DiagnosingEngine" class, especially tne portion below:

// Return the Disease diagnosed
return (Disease) engine.getObjects(new Filter.ByClass(Disease.class)).next();

I need your assistance please!

The whole code is as below:

package voiceexpert;
 
import java.io.Serializable;
 
/**
 *
 * @author Oyelami
 */
public class Symptoms implements Serializable{
    private String s1, s2, s3, result;
    private Disease diseaseobject;
 
    public void setS1(String symptom1)
    {
        this.s1=symptom1;
    }
 
    public void setS2(String symptom2)
    {
        this.s2=symptom2;
    }
    public void setS3(String symptom3)
    {
        this.s3=symptom3;
    }
   public Symptoms()
    {
 
    }
   public Symptoms(String symptom1, String symptom2,String symptom3)
   {
       s1=symptom1;
       s2=symptom2;
       s3=symptom3;
 
   }
   public String getS1()
   {
       return s1;
   }
 
   public String getS2()
   {
       return s2;
   }
 
   public String getS3()
   {
       return s3;
   }
 
 
   public String process()
    {
    DiagnosingEngine engine = new DiagnosingEngine(s1,s2,s3);
    diseaseobject=engine.execute();
    result = diseaseobject.diagnosis;
    return result;
    }
 
 
   public String getResult()
   {
       return result;
   }
 
}// end of class Symptoms

package voiceexpert;
 
public class Disease {
    public String diagnosis;
    public Disease(String thediagnosis)
    {
        diagnosis=thediagnosis;
    }
 
}
 
 
package voiceexpert;
import jess.JessException;
import jess.*;
 
 
public class DiagnosingEngine {
    private Rete engine;
    private WorkingMemoryMarker marker;
    public DiagnosingEngine(String symptom1, String symptom2, String symptom3)
    {
        try{
        // create a Jess rule engine
        engine = new Rete();
        engine.reset();
        //Load the rules
        engine.batch("diagnosingvoice.clp");
        // Create a new Symptom object and initialize with the syptoms supplied by the caller
        Symptoms s =new Symptoms(symptom1, symptom2, symptom3);
        // Load the symptoms into the working memory
        engine.add(s);
        // mArk the end of symptoms for later
        marker = engine.mark();
    } catch(JessException e){}
    }
 
    public Disease execute()
    {
        try{
      // Fire the rules that apply to those symptoms
        engine.run();
            } catch (JessException e){}
 // Return the Disease diagnosed
        return (Disease) engine.getObjects(new Filter.ByClass(Disease.class)).next();
    }
 
}// end of class DiagnosingEngine

Please, can somebody help me out?