public String getCallerReference() {
        return this.callerReference;
    }
<p>
A unique value (for example, a date-time stamp) that ensures that the request can't be replayed.
</p>
<p>
If the value of <code>CallerReference</code> is new (regardless of the content of the
<code>StreamingDistributionConfig</code> object), CloudFront creates a new distribution.
</p>
<p>
If <code>CallerReference</code> is a value that you already sent in a previous request to create a distribution,
CloudFront returns a <code>DistributionAlreadyExists</code> error.
</p>

@return A unique value (for example, a date-time stamp) that ensures that the request can't be replayed.</p>
        <p>
        If the value of <code>CallerReference</code> is new (regardless of the content of the
        <code>StreamingDistributionConfig</code> object), CloudFront creates a new distribution.
        </p>
        <p>
        If <code>CallerReference</code> is a value that you already sent in a previous request to create a
        distribution, CloudFront returns a <code>DistributionAlreadyExists</code> error.
aws-java-sdk-cloudfront/src/main/java/com/amazonaws/services/cloudfront/model/StreamingDistributionConfig.java