setLastReturnValue

   // In practice AbstractEventData is just the abstract class.
   // You must actually use one of the classes that extend it.
    public Object handleEvent(EventFireTime fireTime, AbstractEventData data) {
               
        Object foo = // something here;
        data.setLastReturnValue(foo);
       
        // do something
       
        // The EventFireTime values describe in the documentation what the return
                // value will do, or says nothing about it if the value is ignored
                // If you don't intend to modify the return, always return data.getLastReturnValue();
        return data.getLastReturnValue();
    }