public void setUserName(String userName) {
        this.userName = userName;
    }
<p>
The email address of the user.
</p>
<note>
<p>
Users' email addresses are case-sensitive. During login, if they specify an email address that doesn't use the
same capitalization as the email address specified when their user pool account was created, a
"user does not exist" error message displays.
</p>
</note>

@param userName
       The email address of the user.</p> <note>
       <p>
       Users' email addresses are case-sensitive. During login, if they specify an email address that doesn't use
       the same capitalization as the email address specified when their user pool account was created, a
       "user does not exist" error message displays.
       </p>
aws-java-sdk-appstream/src/main/java/com/amazonaws/services/appstream/model/CreateUserRequest.java