CloudCollectionsListener (Solr 7.7.0 API)

```
public interface CloudCollectionsListener
```
Callback registered with ZkStateReader.registerCloudCollectionsListener(CloudCollectionsListener) and called whenever the cloud's set of collections changes.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`void`	`onChange(Set<String> oldCollections, Set<String> newCollections)`	Called when a collection is created, a collection is deleted or a watched collection's state changes.

- Method Detail
  - onChange
```
void onChange(Set<String> oldCollections,
              Set<String> newCollections)
```
    Called when a collection is created, a collection is deleted or a watched collection's state changes. Note that, due to the way Zookeeper watchers are implemented, a single call may be the result of multiple or no collection creation or deletions. Also, multiple calls to this method can be made with the same set of collections, ie. without any new updates.
    
    Parameters:
    
    oldCollections - the previous set of collections
    
    newCollections - the new set of collections