Since final does different things depending on where it is kotlin decided to use different keywords. val replaces final in variable declarations, open replaces (but does the opposite of) final in method and field declarations. For example:įinal is not a keyword in kotlin. There are required by the basic syntax, and you need to know them for writing basic kotlin code. Some of them replace a keywords java has, usually doing the opposite and/or using more keywords for the different effects it had. You can code in kotlin without knowing the majority of them, but knowing them will surely help you write more idiomatic code. You learn these while you learn the features that use them. Some of them exists for features kotlin has and java not, for example operator, in, data, sealed, suspend, inline, crossinline, noinline, reified, typealias, by, get, set, ecc ecc. Is there a good resource that lists them all? And enum is the same concept as Java's enum, albeit with slightly different syntax. typealias is a way to give a simpler name to a complex type. open is because Kotlin classes are final by default, so you need open to indicate that a class is non-final. data and lateinit are shorthand for boilerplate code that you would end up writing in Java.

Kotlin's multitude of keywords exist to allow us to express things. But the same is true if you stumble across some Java code that uses an unfamiliar library. If you stumble across some Kotlin code that uses unfamiliar keywords, you'll have a hard time understanding what the code does. There's List, InputStream, Parser, PrintWriter, and a lot more that I probably don't know.Īny time you step into a new language, new library, or new technology, you're going to have a lot of things to learn. Why does Java's standard library have so many classes and functions? I generally (as a C developer) find all the classes and functions very confusing.

Kotlin with keyword