private com.google.protobuf.SingleFieldBuilderV3<
            com.google.protobuf.Value,
            com.google.protobuf.Value.Builder,
            com.google.protobuf.ValueOrBuilder>
        getDefaultFieldBuilder() {
      if (defaultBuilder_ == null) {
        defaultBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.protobuf.Value,
                com.google.protobuf.Value.Builder,
                com.google.protobuf.ValueOrBuilder>(
                getDefault(), getParentForChildren(), isClean());
        default_ = null;
      }
      return defaultBuilder_;
    }
<pre>
Optional. Default value of the data.
</pre>

<code>.google.protobuf.Value default = 23 [(.google.api.field_behavior) = OPTIONAL];</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/Schema.java