https://docs.oracle.com/javase/7/docs/technotes/guides/collections/overview.html
Hashset vs TreeSet vs LinkedHashSet
https://dzone.com/articles/hashset-vs-treeset-vs
HashMap vs TreeMap vs LinkedHashMap vs HashTable
https://dzone.com/articles/hashmap-vs-treemap-vs
LinkedList vs Arraylist vs Vector
https://dzone.com/articles/arraylist-vs-linkedlist-vsLinkedIn Learning
https://www.linkedin.com/learning/learning-java-collections/java-collections-framework