org.apache.lucene.index

## Interface IndexReader.CacheHelper

- 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 and 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.

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