public Builder clearUserId() {
      userId_ = getDefaultInstance().getUserId();
      bitField0_ = (bitField0_ & ~0x00000004);
      onChanged();
      return this;
    }
<pre>
Required if
[allow_missing_ids][google.cloud.talent.v4beta1.RequestMetadata.allow_missing_ids]
is unset or `false`.

A unique user identification string, as determined by the client.
To have the strongest positive impact on search quality
make sure the client-level is unique.
Obfuscate this field for privacy concerns before
providing it to the service.

Note that any improvements to the model for a particular tenant site rely
on this field being set correctly to a unique user ID.

The maximum number of allowed characters is 255.
</pre>

<code>string user_id = 3;</code>

@return This builder for chaining.
java-talent/proto-google-cloud-talent-v4beta1/src/main/java/com/google/cloud/talent/v4beta1/RequestMetadata.java