Kotlin: changing job, moving from java. What senior guy should know about kotlin, besides syntax? =)

[edgy tide]

While being a junior java backend developer, got an offer for a senior one.

I'm pretty ok with java, but haven't ever touched kotlin, thus a little scared.
Besides basic syntax, what an average senior guy is expected to know with this language? Must have kotlin-only libs/frameworks? (I know it reuses a lot of java ones, and I'm comfortable with java infrastructure)

I have ~ok level of understanding of system design concepts and stuff, so question is purely on kotlin language

[hollow prism]

<@&1008423204219531294> please have a look, thanks.

[hollow prism]

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[glad sinew]

the java to kotlin switch is fairly easy. but u need about 1 month to familiarize with the new concepts and ideas

and probably another month + practice to get into the kotlin style of writing code

so that u stop writing java code in disguise

kotlin has excellent tutorials on their website for all their fancy stuff

so they will cover u

there are some good books that help getting into the kotlin mindset

for example Effective Kotlin

u can start reading from here

https://kotlinlang.org/docs/basic-syntax.html

and then go through the topics on the left

since ur coming from java, one of the first things ull notice is that kotlin dumped the concept of static

and replaced it by utility classes

which they call object, instead of class

and sth that is very frequently used in kotlin-style code are the scoped functions

https://kotlinlang.org/docs/scope-functions.html

let, run, with, apply, also

which let u write code in a fluent-chain

sometimes very elegant

lambdas look a tad different in kotlin as well, since they introduced them before java did

and there is a shorthand that looks strange at first

if u have a method that takes a lambda as the last argument, u call the method in the following style:

foo(...) {
  ... // lambda body
}

instead of foo(..., lambda)

thats a concept thats super prominent

especially bc the scope functions also use that

Person().apply {
  name = "John"
  age = 25
}.let {
  saveToDatabase(it)
}.also {
  log(it)
}

it is a shorthand for the first parameter in the lambda

so u dont have to name it explicitly

like in java x -> foo(x)

the last line in a lambda is implicitly return ...

so u dont have to write that either

another very prominent concept in kotlin are extension functions

they allow u to add methods to existing classes

for example:

fun String.printMe() {
  println(this)
}

"huhu".printMe()

this idea is heavily made use of to extend the existing java code base with new stuff

and u can use it as well (but dont overdo it)

in fact, a lot of things that look like magic use it

for (i in 1..3) {
  ...
}

this for example uses an infix-extension on Int

infix fun Int.'..'(other : Int) =
  Range(this, other)

looks sth like this

so its a method added to Int, that wants another Int as parameter, and it returns a Range as result

which is iterable

and hence u can iterate over it

and bc of infix, u can write the function as x foo y instead of x.foo(y)

like an operator

sth else thats important is that kotlins collections are all immutable by default

List cant be changed

MutableList can

one extends the other though, so u can switch easily

when is used a lot as well

its a mix between switch and if-else

its quite powerful

since u can write arbitrary expressions in it

and not just fix cases like in java

enjoy ur journey. kotlin feels like java 2.0

it tries to get rid of all issues that annoy java devs

[edgy tide]

Thanks for such a detailed list, but I've already learned all these as part of "basic syntax" thing, and it feels, like there should be many more other concepts?
Things, that you can learn with the experience, like certain practices, that aren't mentioned in these guides. Like how in Java we don't like using inheritance for reusing complex behaviour, or using null for business logic (yes, I know that kotlin handles nulls in special, and a really nice way) This is just an example of what is allowed by language itself, but is considered a bad practice amongst developers

[edgy tide]

Yeah, kotlin feels really really nice and neat. Also feels like one of these modern languages, with clean and accessible documentation and code guidelines. (c++ flashbacks, where there are 50 insane ways to write any single thing)

[glad sinew]

well, i didnt just tell u syntax diffs. i focused on kotlin-esque style stuff

if u just write java code in kotlin-syntax, u will end up with java code in disguise

the kotlin mindset is different

revolving around what i mentioned mostly

u will see a lot of scoped functions and extension functions

[edgy tide]

Yeah, like you can still check x == null, but there are cleaner ways to do that

[glad sinew]

if u know modern java, u probably know Optional

kotlins nullability stuff is similar like that, just more extreme

foo?.bar()

[edgy tide]

one of my fav things, yeah. Also like how kotlin handles it

[glad sinew]

foo ?: 5

and so on

[edgy tide]

I guess I got the Idea. You outlined most important concepts, for which I'm grateful, and the rest would come with experience

[glad sinew]

yeah. u will adapt very quick after u converted a few classes

[edgy tide]

Before I close thread, is there something like Thanks @Zabuzard to give you carma?

[glad sinew]

its automatic, thanks 👍