public DescribeFleetInstancesResult withActiveInstances(java.util.Collection<ActiveInstance> activeInstances) {
        setActiveInstances(activeInstances);
        return this;
    }
<p>
The running instances. This list is refreshed periodically and might be out of date.
</p>

@param activeInstances
       The running instances. This list is refreshed periodically and might be out of date.
@return Returns a reference to this object so that method calls can be chained together.
aws-java-sdk-ec2/src/main/java/com/amazonaws/services/ec2/model/DescribeFleetInstancesResult.java