public void setMasterUsername(String masterUsername) {
        this.masterUsername = masterUsername;
    }
<p>
The name of the master user for the DB cluster.
</p>
<p>
Valid for Cluster Type: Aurora DB clusters and Multi-AZ DB clusters
</p>
<p>
Constraints:
</p>
<ul>
<li>
<p>
Must be 1 to 16 letters or numbers.
</p>
</li>
<li>
<p>
First character must be a letter.
</p>
</li>
<li>
<p>
Can't be a reserved word for the chosen database engine.
</p>
</li>
</ul>

@param masterUsername
       The name of the master user for the DB cluster.</p>
       <p>
       Valid for Cluster Type: Aurora DB clusters and Multi-AZ DB clusters
       </p>
       <p>
       Constraints:
       </p>
       <ul>
       <li>
       <p>
       Must be 1 to 16 letters or numbers.
       </p>
       </li>
       <li>
       <p>
       First character must be a letter.
       </p>
       </li>
       <li>
       <p>
       Can't be a reserved word for the chosen database engine.
       </p>
       </li>
aws-java-sdk-rds/src/main/java/com/amazonaws/services/rds/model/CreateDBClusterRequest.java