public final OperationFuture<Subnet, OperationMetadata> updateSubnetAsync(
      Subnet subnet, FieldMask updateMask) {
    UpdateSubnetRequest request =
        UpdateSubnetRequest.newBuilder().setSubnet(subnet).setUpdateMask(updateMask).build();
    return updateSubnetAsync(request);
  }
Updates the parameters of a single subnet. Only fields specified in `update_mask` are applied.

<p>&#42;Note&#42;: This API is synchronous and always returns a successful
`google.longrunning.Operation` (LRO). The returned LRO will only have `done` and `response`
fields.

<p>Sample code:

<pre>{@code
// This snippet has been automatically generated and should be regarded as a code template only.
// It will require modifications to work:
// - It may require correct/in-range values for request initialization.
// - It may require specifying regional endpoints when creating the service client as shown in
// https://cloud.google.com/java/docs/setup#configure_endpoints_for_the_client_library
try (VmwareEngineClient vmwareEngineClient = VmwareEngineClient.create()) {
  Subnet subnet = Subnet.newBuilder().build();
  FieldMask updateMask = FieldMask.newBuilder().build();
  Subnet response = vmwareEngineClient.updateSubnetAsync(subnet, updateMask).get();
}
}</pre>

@param subnet Required. Subnet description.
@param updateMask Required. Field mask is used to specify the fields to be overwritten in the
    `Subnet` resource by the update. The fields specified in the `update_mask` are relative to
    the resource, not the full request. A field will be overwritten if it is in the mask. If
    the user does not provide a mask then all fields will be overwritten.
@throws com.google.api.gax.rpc.ApiException if the remote call fails
java-vmwareengine/google-cloud-vmwareengine/src/main/java/com/google/cloud/vmwareengine/v1/VmwareEngineClient.java