private com.google.protobuf.SingleFieldBuilderV3<
              com.google.storagetransfer.v1.proto.TransferTypes.TransferSpec,
              com.google.storagetransfer.v1.proto.TransferTypes.TransferSpec.Builder,
              com.google.storagetransfer.v1.proto.TransferTypes.TransferSpecOrBuilder>
          getTransferSpecFieldBuilder() {
        if (transferSpecBuilder_ == null) {
          transferSpecBuilder_ =
              new com.google.protobuf.SingleFieldBuilderV3<
                  com.google.storagetransfer.v1.proto.TransferTypes.TransferSpec,
                  com.google.storagetransfer.v1.proto.TransferTypes.TransferSpec.Builder,
                  com.google.storagetransfer.v1.proto.TransferTypes.TransferSpecOrBuilder>(
                  getTransferSpec(), getParentForChildren(), isClean());
          transferSpec_ = null;
        }
        return transferSpecBuilder_;
      }
<pre>
Transfer specification.
</pre>

<code>.google.storagetransfer.v1.TransferSpec transfer_spec = 3;</code>
java-storage-transfer/proto-google-cloud-storage-transfer-v1/src/main/java/com/google/storagetransfer/v1/proto/TransferTypes.java