It's fascinating to me looking at beginning language guides and thinking "what does this say about the culture of the language"
When I was delving into #OCaml it was (with affection) "here's hello world and here's a dense academic paper on implementing event systems in OCaml 5!"
#Java guides used to be centered on the assumption that you were a web programmer looking to do applets, even long after that assumption died.
#RustLang generally seems to assume a background in programming w/ a CLI.
Java has a interface* called “Set” but the documentation is nebulous & ominous. “may throw an exception” what? does no one even know? There isn’t even a method for intersection & union?! What is the point? I taught my students to use the set object in Python. It was an elegant beautiful experience— Thought we could do it in Java but I think I will just use arraylist, write my own damn methods.
I’m biased, but Java is always more annoying like this. ugh. (*this explains part of my confusion)
In Java, "Set" is an interface. What you are looking for is a "HashSet" https://docs.oracle.com/javase/8/docs/api/java/util/HashSet.html or any other class that implements the interface "Set" like a TreeSet, LinkedHashSet, CopyOnWriteArraySet, EnumSet, and others, such as a Map's key set.
A weird thing about being 50 is that there are programming languages that I've used regularly for longer than some of the software developers I work with have been alive. I first wrote BASIC code in the 1980s. The first time I wrote an expression evaluator--a fairly standard programming puzzle or homework--was in 1990. I wrote it in Pascal for an undergraduate homework assignment. I first wrote perl in the early 1990s, when it was still perl 4.036 (5.38.2 now). I first wrote java in 1995-ish, when it was still java 1.0 (1.21 now). I first wrote scala, which I still use for most things today, in 2013-ish, when it was still scala 2.8 (3.4.0 now). At various times I've been "fluent" in 8086 assembly, BASIC, C, Pascal, perl, python, java, scala; and passable in LISP/Scheme, Prolog, old school Mathematica, (early days) Objective C, matlab/octave, and R. I've written a few lines of Fortran and more than a few lines of COBOL that I ran in a production system once. I could probably write a bit of Haskell if pressed but for some reason I really dislike its syntax so I've never been enthusiastic about learning it well. I've experimented with Clean, Flix, Curry, Unison, Factor, and Joy and learned bits and pieces of each of those. I'm trying to decide whether I should try learning Idris, Agda, and/or Lean. I'm pretty sure I'm forgetting a few languages. Bit of 6502 assembly long ago. Bit of Unix/Linux shell scripting languages (old enough to have lived and breathed tcsh before switching to bash; I use fish now mostly).
When I say passable: in graduate school I wrote a Prolog interpreter in java (including parsing source code or REPL input), within which I could run the classic examples like append or (very simple) symbolic differentiation/integration. As an undergraduate I wrote a Mathematica program to solve the word recognition problem for context-free formal languages. But I'd need some study time to be able to write these languages again.
I don't know what the hell prompted me to reminisce about programming languages. I hope it doesn't come off as a humblebrag but rather like old guy spinning yarns. I think I've been through so many because I'm never quite happy with any one of them and because I've had a varied career that started when I was pretty young.
I guess I'm also half hoping to find people on here who have similar interests so I'm going to riddle this post with hashtags: