code: public void addServiceIfNotPresent(WiFiP2pService service) {
          WfdLog.d(TAG, "addServiceIfNotPresent BEGIN, with size = " + serviceList.size());
  
          if (service == null) {
              WfdLog.e(TAG, "Service is null, returning...");
              return;
          }
  
          boolean add = true;
          for (WiFiP2pService element : serviceList) {
              if (element != null
                      && element.getDevice().equals(service.getDevice())
                      && element.getInstanceName().equals(service.getInstanceName())) {
                  add = false; //already in the list
              }
          }
  
          if (add) {
              serviceList.add(service);
          }
  
          WfdLog.d(TAG, "addServiceIfNotPresent END, with size = " + serviceList.size());
      }
docs: Method to add a service inside the list in a secure way.
  The service is added only if isn't already inside the list.
  
  @param service {@link WiFiP2pService} to add.