public DescribeFleetInstancesResult withActiveInstances(ActiveInstance... activeInstances) {
        if (this.activeInstances == null) {
            setActiveInstances(new com.amazonaws.internal.SdkInternalList<ActiveInstance>(activeInstances.length));
        }
        for (ActiveInstance ele : activeInstances) {
            this.activeInstances.add(ele);
        }
        return this;
    }
<p>
The running instances. This list is refreshed periodically and might be out of date.
</p>
<p>
<b>NOTE:</b> This method appends the values to the existing list (if any). Use
{@link #setActiveInstances(java.util.Collection)} or {@link #withActiveInstances(java.util.Collection)} if you
want to override the existing values.
</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 This list is refreshed periodically and might be out of date.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