@java.lang.Override
  public java.lang.String getRevisionId() {
    java.lang.Object ref = revisionId_;
    if (ref instanceof java.lang.String) {
      return (java.lang.String) ref;
    } else {
      com.google.protobuf.ByteString bs = (com.google.protobuf.ByteString) ref;
      java.lang.String s = bs.toStringUtf8();
      revisionId_ = s;
      return s;
    }
  }
<pre>
Optional. The revision of the workflow to retrieve. If the revision_id is
empty, the latest revision is retrieved.
The format is "000001-a4d", where the first six characters define
the zero-padded decimal revision number. They are followed by a hyphen and
three hexadecimal characters.
</pre>

<code>string revision_id = 2 [(.google.api.field_behavior) = OPTIONAL];</code>

@return The revisionId.
java-workflows/proto-google-cloud-workflows-v1/src/main/java/com/google/cloud/workflows/v1/GetWorkflowRequest.java