code: public boolean existsOnBroker (String brokerId) {
          boolean result = false;
  
          PerBrokerInfo info;
          synchronized (this.brokerDetails) {
              info = this.brokerDetails.get(brokerId);
          }
  
          if ((info != null) && (info.exists)) {
              result = true;
          }
  
          return result;
      }
docs: Determine whether this destination exists on the broker with the given ID.
  
  @param brokerId ID of the broker on which to check for existence of the destination.
  @return true => if the destination exists on the broker with the given ID; false if the destination does not
  exist on the broker with the given ID regardless of whether the destination has even been seen on the same
  broker.