public String getPreferredAuthenticationMethod() {
        return this.preferredAuthenticationMethod;
    }
<p>
The preferred authentication method, with valid values "KEY" or "TOKEN". If a value isn't provided then the
<b>DefaultAuthenticationMethod</b> is used.
</p>

@return The preferred authentication method, with valid values "KEY" or "TOKEN". If a value isn't provided then
        the <b>DefaultAuthenticationMethod</b> is used.
aws-java-sdk-pinpoint/src/main/java/com/amazonaws/services/pinpoint/model/GCMMessage.java