Performance comparison for various implementation - http://java-performance.info/hashmap-overview-jdk-fastutil-goldman-sachs-hppc-koloboke-trove-january-2015/

Java Hashtable, HashMap, ConcurrentHashMap – Performance impact - https://blog.fastthread.io/2022/04/22/java-hashtable-hashmap-concurrenthashmap-performance-impact/

http://marxsoftware.blogspot.com/2015/12/discovering-trove.html

Using Red-Black tree in Map - https://dzone.com/articles/java-8-hashmaps-keys-and-the-comparable-interface