private com.google.protobuf.SingleFieldBuilderV3<
              com.google.storagetransfer.v1.proto.TransferTypes.HdfsData,
              com.google.storagetransfer.v1.proto.TransferTypes.HdfsData.Builder,
              com.google.storagetransfer.v1.proto.TransferTypes.HdfsDataOrBuilder>
          getHdfsDataSourceFieldBuilder() {
        if (hdfsDataSourceBuilder_ == null) {
          if (!(dataSourceCase_ == 20)) {
            dataSource_ =
                com.google.storagetransfer.v1.proto.TransferTypes.HdfsData.getDefaultInstance();
          }
          hdfsDataSourceBuilder_ =
              new com.google.protobuf.SingleFieldBuilderV3<
                  com.google.storagetransfer.v1.proto.TransferTypes.HdfsData,
                  com.google.storagetransfer.v1.proto.TransferTypes.HdfsData.Builder,
                  com.google.storagetransfer.v1.proto.TransferTypes.HdfsDataOrBuilder>(
                  (com.google.storagetransfer.v1.proto.TransferTypes.HdfsData) dataSource_,
                  getParentForChildren(),
                  isClean());
          dataSource_ = null;
        }
        dataSourceCase_ = 20;
        onChanged();
        return hdfsDataSourceBuilder_;
      }
<pre>
An HDFS cluster data source.
</pre>

<code>.google.storagetransfer.v1.HdfsData hdfs_data_source = 20;</code>
java-storage-transfer/proto-google-cloud-storage-transfer-v1/src/main/java/com/google/storagetransfer/v1/proto/TransferTypes.java