private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.vmwareengine.v1.Subnet,
            com.google.cloud.vmwareengine.v1.Subnet.Builder,
            com.google.cloud.vmwareengine.v1.SubnetOrBuilder>
        getSubnetFieldBuilder() {
      if (subnetBuilder_ == null) {
        subnetBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.vmwareengine.v1.Subnet,
                com.google.cloud.vmwareengine.v1.Subnet.Builder,
                com.google.cloud.vmwareengine.v1.SubnetOrBuilder>(
                getSubnet(), getParentForChildren(), isClean());
        subnet_ = null;
      }
      return subnetBuilder_;
    }
<pre>
Required. Subnet description.
</pre>

<code>
.google.cloud.vmwareengine.v1.Subnet subnet = 2 [(.google.api.field_behavior) = REQUIRED];
</code>
java-vmwareengine/proto-google-cloud-vmwareengine-v1/src/main/java/com/google/cloud/vmwareengine/v1/UpdateSubnetRequest.java