public Builder setOverwriteWhen(
          com.google.storagetransfer.v1.proto.TransferTypes.TransferOptions.OverwriteWhen value) {
        if (value == null) {
          throw new NullPointerException();
        }
        bitField0_ |= 0x00000008;
        overwriteWhen_ = value.getNumber();
        onChanged();
        return this;
      }
<pre>
When to overwrite objects that already exist in the sink. If not set,
overwrite behavior is determined by
[overwrite_objects_already_existing_in_sink][google.storagetransfer.v1.TransferOptions.overwrite_objects_already_existing_in_sink].
</pre>

<code>.google.storagetransfer.v1.TransferOptions.OverwriteWhen overwrite_when = 4;</code>

@param value The overwriteWhen to set.
@return This builder for chaining.
java-storage-transfer/proto-google-cloud-storage-transfer-v1/src/main/java/com/google/storagetransfer/v1/proto/TransferTypes.java