public Builder setChannelId(java.lang.String value) {
          if (value == null) {
            throw new NullPointerException();
          }
          channelId_ = value;
          bitField0_ |= 0x00000001;
          onChanged();
          return this;
        }
<pre>
Required. The Slack channel ID.
</pre>

<code>string channel_id = 1 [(.google.api.field_behavior) = REQUIRED];</code>

@param value The channelId to set.
@return This builder for chaining.
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/SlackSource.java