code: public Observable<Void> acquireAsync(String resourceGroupName, String serverName, String dnsAliasName, String oldServerDnsAliasId) {
          return acquireWithServiceResponseAsync(resourceGroupName, serverName, dnsAliasName, oldServerDnsAliasId).map(new Func1<ServiceResponse<Void>, Void>() {
              @Override
              public Void call(ServiceResponse<Void> response) {
                  return response.body();
              }
          });
      }
docs: Acquires server DNS alias from another server.
  
  @param resourceGroupName The name of the resource group that contains the resource. You can obtain this value from the Azure Resource Manager API or the portal.
  @param serverName The name of the server that the alias is pointing to.
  @param dnsAliasName The name of the server dns alias.
  @param oldServerDnsAliasId The id of the server alias that will be acquired to point to this server instead.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable for the request