public Builder setTtl(com.google.protobuf.Duration value) {
      if (ttlBuilder_ == null) {
        if (value == null) {
          throw new NullPointerException();
        }
        expiration_ = value;
        onChanged();
      } else {
        ttlBuilder_.setMessage(value);
      }
      expirationCase_ = 14;
      return this;
    }
<pre>
Input only. The time-to-live (TTL) or duration for the subscription. If
unspecified or set to `0`, uses the maximum possible duration.
</pre>

<code>.google.protobuf.Duration ttl = 14 [(.google.api.field_behavior) = INPUT_ONLY];</code>
java-workspaceevents/proto-google-cloud-workspaceevents-v1/src/main/java/com/google/apps/events/subscriptions/v1/Subscription.java