I’ve been exploring Kotlin recently. Kotlin is a new statically typed JVM language and was announced about half a year ago. This month JetBrains released its first milestone candidate which I decided to have a closer look at.

First of Kotlin is still in its early stages. A lot of things work pretty well (I’m especially impressed by the IDE support) but there are still numerous issues. I’ve hit a couple of bugs so far.

Features
I’ll highlight a few language features which I think are interesting (coming from Java).

Null-safety

    fun demoVars() {
        val first : String = "abc"
        first = "xyz" // error, variable is immutable
        var second = "abc"
        second = null // error, variable is mutable but non-nullable
        var third : String? = "abc"
        third = null  // ok, variable is marked as nullable ('?')

        foo?.bar?.baz // safe navigation
    }

Multi-line strings and string templates

    fun demoMultiLineTemplate() {
        val first = "john"
        val second = "doe"
        println("""
          First name: $first
          Second name: $second
        """)
    }

Higher-order functions

    bar({ println("I'm foobar") })
    bar({ println("I'm foobar") }, { println("I'm foobaz") })

    fun  bar(foobar : () -> T) {
        foobar()
    }

    fun  bar(foobar : () -> T, foobaz : () -> B) {
        foobar()
        foobaz()
    }

These a just some examples refer to the Kotlin docs for more features.

Next blog
In my next blog I’ll show a larger example of Kotlin code and compare it with its Java equivalent.