*
   * <p><b>Java 8+ users:</b> many use cases for this method are better addressed by {@link
   * java.util.stream.Stream#filter}. This method is not being deprecated, but we gently encourage
   * you to migrate to streams.
   */
  // TODO(kevinb): how to omit that last sentence when building GWT javadoc?
  public static <E extends @Nullable Object> Set<E> filter(
      Set<E> unfiltered, Predicate<? super E> predicate) {

- If upgrading Cluster Federation components from 1.3.x, be aware the federation-controller-manager now looks for a different secret name.  Run the following to migrate (#28938, @madhusudancs)

```
kubectl --namespace=federation get secret federation-apiserver-secret -o json | sed 's/federation-apiserver-secret/federation-apiserver-kubeconfig/g' | kubectl create -f -

  - NetworkPolicy resources will no longer be served from `extensions/v1beta1` in v1.16. Migrate use to the `networking.k8s.io/v1` API, available since v1.8. Existing persisted data can be retrieved via the `networking.k8s.io/v1` API.
  - PodSecurityPolicy resources will no longer be served from `extensions/v1beta1` in v1.16. Migrate to the `policy/v1beta1` API, available since v1.10. Existing persisted data can be retrieved via the `policy/v1beta1` API.

- Migrated the `nodevolumelimits` scheduler plugin to use [contextual logging](https://k8s.io/docs/concepts/cluster-administration/system-logs/#contextual-logging). ([#116884](https://github.com/kubernetes/kubernetes/pull/116884), [@mengjiao-liu](https://github.com/mengjiao-liu))

- Action-required: kubeadm: remove the deprecated feature --experimental-kustomize from kubeadm commands. The feature was replaced with --experimental-patches in 1.19. To migrate see the --help description for the --experimental-patches flag. ([#94871](https://githu...

#### User Provided Extensions
* [beta] ThirdPartyResource is deprecated. Please migrate to the successor, CustomResourceDefinition. For more information, see [Custom Resources](https://kubernetes.io/docs/concepts/api-extension/custom-resources/) and [Migrate a ThirdPartyResource to CustomResourceDefinition](https://kubernetes.io/docs/tasks/access-kubernetes-api/migrate-third-party-resource/).

- The beta `PodSecurityPolicy` admission plugin, deprecated since 1.21, is removed. Follow the instructions at https://kubernetes.io/docs/tasks/configure-pod-container/migrate-from-psp/ to migrate to the built-in PodSecurity admission plugin (or to another third-party  policy webhook) prior to upgrading to v1.25. ([#109798](https://github.com/kubernetes/kubernetes/pull/109798), [@liggitt](https://github.com/liggitt))

* There's a known issue where the Vertical Pod Autoscaler will radically change implementation in 1.12, so users of VPA (alpha) in 1.11 are warned that they will not be able to automatically migrate their VPA configs from 1.11 to 1.12.


## Before Upgrading

  - Ingress resources will no longer be served from `extensions/v1beta1` in v1.20. Migrate use to the `networking.k8s.io/v1beta1` API, available since v1.14. Existing persisted data can be retrieved via the `networking.k8s.io/v1beta1` API.

- Adds "volume.beta.kubernetes.io/migrated-to" annotation to PV's and PVC's when they are migrated to signal external provisioners to pick up those objects for Provisioning and Deleting. ([#87098](https://github.com/kubernetes/kubernetes/pull/87098), [@davidz627](https://github.com/davidz627)) [SIG  Storage]