public Builder setUserId(java.lang.String value) {
      if (value == null) {
        throw new NullPointerException();
      }
      userId_ = value;
      bitField0_ |= 0x00000004;
      onChanged();
      return this;
    }
<pre>
Required if
[allow_missing_ids][google.cloud.talent.v4.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>

@param value The userId to set.
@return This builder for chaining.
java-talent/proto-google-cloud-talent-v4/src/main/java/com/google/cloud/talent/v4/RequestMetadata.java