IndexReader.CacheHelper (Lucene 8.1.0 API)

Enclosing class:

IndexReader
```
public static interface IndexReader.CacheHelper
```
A utility class that gives hooks in order to help build a cache based on the data that is contained in this index.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`void`	`addClosedListener(IndexReader.ClosedListener listener)`	Add a `IndexReader.ClosedListener` which will be called when the resource guarded by `getKey()` is closed.
`IndexReader.CacheKey`	`getKey()`	Get a key that the resource can be cached on.

- Method Detail
  - getKey
```
IndexReader.CacheKey getKey()
```
    Get a key that the resource can be cached on. The given entry can be compared using identity, ie. Object.equals(java.lang.Object) is implemented as == and Object.hashCode() is implemented as System.identityHashCode(java.lang.Object).
  - addClosedListener
```
void addClosedListener(IndexReader.ClosedListener listener)
```
    Add a IndexReader.ClosedListener which will be called when the resource guarded by getKey() is closed.