code: public Observable<ExpressRouteCircuitConnectionInner> getAsync(String resourceGroupName, String circuitName, String peeringName, String connectionName) {
          return getWithServiceResponseAsync(resourceGroupName, circuitName, peeringName, connectionName).map(new Func1<ServiceResponse<ExpressRouteCircuitConnectionInner>, ExpressRouteCircuitConnectionInner>() {
              @Override
              public ExpressRouteCircuitConnectionInner call(ServiceResponse<ExpressRouteCircuitConnectionInner> response) {
                  return response.body();
              }
          });
      }
docs: Gets the specified Express Route Circuit Connection from the specified express route circuit.
  
  @param resourceGroupName The name of the resource group.
  @param circuitName The name of the express route circuit.
  @param peeringName The name of the peering.
  @param connectionName The name of the express route circuit connection.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the ExpressRouteCircuitConnectionInner object