async-http-client, https://github.com/AsyncHttpClient/async-http-client, accessed Oct 2023.
Some threads on StackOverflow: https://stackoverflow.com/questions/16539245/java-equivalent-of-c-sharp-async-await, https://stackoverflow.com/questions/16349797/can-asynchttpclient-perform-non-blocking-async-http-calls?rq=3, https://stackoverflow.com/questions/3142915/how-do-you-create-an-asynchronous-http-request-in-java?rq=3
Other references: https://onecompiler.com/cheatsheets/async-http-client, https://www.tornadoweb.org/en/stable/httpclient.html, http://www.java2s.com/example/java-api/org/apache/http/impl/nio/client/closeablehttpasyncclient/index.html