public void setNextActivity(String nextActivity) {
        this.nextActivity = nextActivity;
    }
<p>
The unique identifier for the next activity to perform, after the message is sent.
</p>

@param nextActivity
       The unique identifier for the next activity to perform, after the message is sent.
aws-java-sdk-pinpoint/src/main/java/com/amazonaws/services/pinpoint/model/EmailMessageActivity.java