private com.google.protobuf.SingleFieldBuilderV3<
            com.google.protobuf.Duration,
            com.google.protobuf.Duration.Builder,
            com.google.protobuf.DurationOrBuilder>
        getDurationFieldBuilder() {
      if (durationBuilder_ == null) {
        durationBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.protobuf.Duration,
                com.google.protobuf.Duration.Builder,
                com.google.protobuf.DurationOrBuilder>(
                getDuration(), getParentForChildren(), isClean());
        duration_ = null;
      }
      return durationBuilder_;
    }
<pre>
Output only. Measures the duration of the execution.
</pre>

<code>.google.protobuf.Duration duration = 12 [(.google.api.field_behavior) = OUTPUT_ONLY];
</code>
java-workflow-executions/proto-google-cloud-workflow-executions-v1/src/main/java/com/google/cloud/workflows/executions/v1/Execution.java