Default Java 8 Map implementation is merely: "get X. if X absent, compute for X, put X." These lines of code have been written over and over again for anyone us

Default Java 8 Map implementation is merely: "get X. if X absent, compute for X, put X." These lines of code have been written over and over again for anyone using a Map in Java, no doubt. It is entirely trivial and almost impossible to get wrong writing it out on your own. Whereas writing a performant concurrent "computeIfAbsent" is extremely non-trivial and if you try to do it yourself, you have a high chance of getting it wrong or slow. Therefore, CHM "computeIfAbsent" is new and exciting, and Map "computeIfAbsent" is "could care less".