https://lucene.apache.org/core/7_7_2/core/org/apache/lucene/util/WeakIdentityMap.html
WeakIdentityMap (Lucene 7.7.2 API)
luceneapi
https://lucene.apache.org/core/5_3_1/core/org/apache/lucene/util/WeakIdentityMap.html
WeakIdentityMap (Lucene 5.3.1 API)
luceneapi