public Builder clearUserId() {
      userId_ = getDefaultInstance().getUserId();
      bitField0_ = (bitField0_ & ~0x00000002);
      onChanged();
      return this;
    }
<code>string user_id = 2;</code>
@return This builder for chaining.
examples/client/src/main/java/com/clickhouse/examples/protos/UIEvent.java