public java.util.List<PlacementGroupConfig> getPlacementGroups() {
        if (placementGroups == null) {
            placementGroups = new com.amazonaws.internal.SdkInternalList<PlacementGroupConfig>();
        }
        return placementGroups;
    }
<p>
Placement group configured for an Amazon EMR cluster.
</p>

@return Placement group configured for an Amazon EMR cluster.
aws-java-sdk-emr/src/main/java/com/amazonaws/services/elasticmapreduce/model/Cluster.java