@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>
Output only. The revision of the workflow.
A new revision of a workflow is created as a result of updating the
following properties of a workflow:

- [Service account][google.cloud.workflows.v1beta.Workflow.service_account]
- [Workflow code to be
executed][google.cloud.workflows.v1beta.Workflow.source_contents]

The format is "000001-a4d", where the first 6 characters define
the zero-padded revision ordinal number. They are followed by a hyphen and
3 hexadecimal random characters.
</pre>

<code>string revision_id = 4 [(.google.api.field_behavior) = OUTPUT_ONLY];</code>

@return The revisionId.
java-workflows/proto-google-cloud-workflows-v1beta/src/main/java/com/google/cloud/workflows/v1beta/Workflow.java