A design and coding question: If some1 can help

Hi all,

I got into an infinite loop problem when trying to do the following:

// Result
public class Result
{
   private List<Listener> listeners = new ArrayList<Listener>();
   private List<String> log = new ArrayList<String();

   public void addListener(Listener listener)
   {
       list.add(listener);
   }

   public void add(String str)
   {
      // allows the use of listener to process the result. This is
like an observer/observable
      // pattern
      log.add(str);
      for(Listener each: listeners)
      {
         each.add(str);
      }
   }
}

// Task - each task has it owns result instance.
public class Task
{
   private Result result = new Result();
   public Result getResult()
   {
      return result();
   }
}

// ProblematicConstruct
public class ProblematicConstruct implements Listener
{
   private Result result;
   Problem(Result result)
   {
      this.result = result
   }

   public void add(String s)
   {
      //?????????? this will goes into an infinite loop ???????
      result.add(s);
   }
}

Can some one gives some advice or help on how to resolve it? Since
there is not way to restrict people from doing the above Problematic
construct.

Thanks,
Kae