Created by: larrydiamond
This is a series of minor performance boost by replacing the keySet + get calls with entrySet in order to eliminate N lookups in a few places.
In addition, some TreeMap/Set objects were replaced with ConcurrentSkipListMap/Set types which are generally faster and intended to be a replacement when introduced with Java 1.6. https://www.javacodegeeks.com/2017/04/simple-map-iterator-performance-test.html for some nice charts of the performance differences.
I ran all of the unit tests, and I was a little surprised to see pre-existing PMD issues. I did not add any new ones but there are existing ones.
I did review and follow the contribution guidelines and ran the samples. There were no file changes as a result of running the samples, which did not surprise me as this is a performance improvement only - there should be no changes in any output and there was not.
This contribution is against master, please let me know if I did this against the right branch or if I should be doing this work against a different branch.
This is my first pull request to openapi-generator, please excuse any expected actions I did not perform prior to sending this pull request, I will gladly make any changes to fulfill the process to commit code.
Thank you very much, Larry Diamond