if (sipListener == this.sipListener) { this.sipListener = null; } }
if (sipListener == this.sipListener) { this.sipListener = null; }  boolean found = false;  for (Iterator it = sipStack.getSipProviders(); it.hasNext();) { SipProviderImpl nextProvider = (SipProviderImpl) it.next(); if (nextProvider.sipListener != null) found = true; } if (!found) { sipStack.sipListener = null; } }
    public void removeSipListener(SipListener sipListener) {        if (sipListener == this.sipListener) {            this.sipListener = null;        }    }