guava

I've implemented multiple production versions of this problem (but not in JavaScript)[1], so maybe my view of this problem is miscalibrated... This feels both too easy and too hard for an interview? I would expect almost any new grad to be able to implement this in the language of their choice. Adding delays makes it less trivial, except that the answer is... Just use the function provided by the language. That's the right answer for real code, but what are you really assessing by asking it? [1] https://github.com/google/guava/blob/master/guava/src/com/go...

Sorry for the slow reply here, but in Java, “final” variables can’t be updated to reference a different object, but the underlying object can be modified with method calls (e.g. you can append things to a “final” ArrayList, whereas in C++ you can’t append to a const vector. In C++, you mark methods const to indicate that they don’t mutate the underlying object, and only cost methods can be called on const variables). The Guava docs give an example of the defensive copying: https://github.com/google/guava/wiki/ImmutableCollectionsExp.... Any time an Immutable collection is created from another collection, the elements are deep-copied to avoid the possibility that they’re modified elsewhere, even if there’s no possibility of that happening. Even if you’re using e.g. an ImmutableList.Builder, the elements are copied when they’re Add()ed to t