I'd expect any dev wanting a job using a language he doesn't know to have some understanding all of the concepts you're talking about. It's not language specific, it's just the basics of programming.
lol, if I were java dev I'd be pissed off.
honestly this unsound argument that dev which knows more languages is better just because of that needs to die.
Concepts are above languages
You don't have to know languages in order to be familiar with the concepts.
Additionally certain languages do not offer real value to the other
For example I've been writing shitton of C# and from time to time I jumped to js/lua
Messing with those languages didnt gave me anything except pain.
Meanwhile one harder project can give you times, times more - try writing browser, compiler, etc.
__________
Software engineering is deeper and more important than fancy language features and handier ways to express things.
But yea, it's easier to mess with people about their lack of understanding of monad than
arguing about system design, practices & approaches to system modeling cuz they do require context :)
If you only ever coded in a language that doesn't even offer you the ability to tinker with some concepts, you can't be familiar with those. Reading one article about it without ever touching code, is not being familiar with a programming concept.
I'm not saying you should know 10 languages, but if you want to be anything more than a frontend dev or a bad web dev, you need to be exposed to more than 1 language IMHO. I'm not saying you should be an expert, or used multiples languages for years, but at least trying other languages with concepts not available in your favorite language.
Ive jumped from web/desktop dev
to semiconductor industry and worked with the same language.
And the biggest problem was lack of the domain knowledge, not langs.
You can find various langs being used in various places to the point that sometimes you'd be shocked
I disagree, you're familiar by definition.
You're just not experienced and may be not aware of pros and cons unless the article/book/w.e showed them.
Whether experience is important is up to the thing you're talking about.
For example: stealing Result<T> from other language to replace exceptions in your language doesn't require you to use Result<T> impl. in other lang.
I'm a polyglot but Java is the language I used the most and I can guarantee you there are many professional dev I met and worked with that only know Java and make their comfy living writing only Java. Java is powering the real world since more than two decades now and the JVM is some rock solid tech with extensive tooling, so they can get away with only knowing Java.
A dev can definitely focus only on Java and, for better or worse, makes all his career, from his first job until retirement (to me it's obvious Java is here to stay and it's going to dwarf COBOL's legacy), writing only Java.
Not all programming jobs require a PhD in computer science. There's plenty of people out there writing line-of-business software, and that's the stuff that makes the world work.
You surely are, everyone who gets money for developing applications is.
FYI, functional programing and low-level programming isn't even a part of the curriculum in some universities, let alone bootcamps.
(Also, there are tons of languages that don't touch on functional programming concept at all.)
"Professional" means "paid to do it", so, yeah, there's plenty of professional Java developers.
Hum... Do you write programs in exchange for money?