Method PurgeAllCaches

EXPERT: Instructs the FieldCache to forcibly expunge all entries from the underlying caches. This is intended only to be used for test methods as a way to ensure a known base state of the Cache (with out needing to rely on GC to free WeakReferences).
It should not be relied on for "Cache maintenance" in general application code.

EXPERIMENTAL API: This API is considered extremely advanced and experimental. It may be removed or altered w/o warning in future releases of Lucene.