public String getStackId() {
        return this.stackId;
    }
<p>
A stack ID. If you use this parameter, <code>DescribeInstances</code> returns descriptions of the instances
associated with the specified stack.
</p>

@return A stack ID. If you use this parameter, <code>DescribeInstances</code> returns descriptions of the
        instances associated with the specified stack.
aws-java-sdk-opsworks/src/main/java/com/amazonaws/services/opsworks/model/DescribeInstancesRequest.java