public String getOperationId() {
        return this.operationId;
    }
<p>
The unique identifier for this stack set operation.
</p>
<p>
If you don't specify an operation ID, the SDK generates one automatically.
</p>
<p>
The operation ID also functions as an idempotency token, to ensure that CloudFormation performs the stack set
operation only once, even if you retry the request multiple times. You can retry stack set operation requests to
ensure that CloudFormation successfully received them.
</p>
<p>
Repeating this stack set operation with a new operation ID retries all stack instances whose status is
<code>OUTDATED</code>.
</p>

@return The unique identifier for this stack set operation.</p>
        <p>
        If you don't specify an operation ID, the SDK generates one automatically.
        </p>
        <p>
        The operation ID also functions as an idempotency token, to ensure that CloudFormation performs the stack
        set operation only once, even if you retry the request multiple times. You can retry stack set operation
        requests to ensure that CloudFormation successfully received them.
        </p>
        <p>
        Repeating this stack set operation with a new operation ID retries all stack instances whose status is
        <code>OUTDATED</code>.
aws-java-sdk-cloudformation/src/main/java/com/amazonaws/services/cloudformation/model/DeleteStackInstancesRequest.java