Kotlin 速記

1. Variable:

var a = 10
val b = 10
var c: Int = 10

2. Format String:

val name = "cat"
println("Hello ${name}")

3. Function:

fun greet(name: String=""): Unit {
    println("Hello ${name}")
}

fun greet(name: String=""): Unit =
    println("Hello ${name}")

4. For loop/ For in:

for(i in [..|until|] [step]) {}

val lst = listOf(1, 2, 3)
for(it in lst) println("item: ${it}")

val m = mapOf(
        "Hello" to "world", "apple" to "banana")
for((k, v) in m) println("key: ${k}, val: ${v}")

5. Lambda:

val greet = { name:String -> println("Hello ${name}") }
greet("Carto")

6. Funtional style:

val lst = listOf(10, 20, 11, 30)
lst.forEach { it -> println(it) }
val odd = lst.filter { it %2 != 0 }
val double = lst.map { it -> it*2 }

7. DTOs, class, object and abstract:

data class Dog(val name:String, val age:Int) {}

fun main(args: Array<String>) {
    val d1 = Dog("Doggy", 10)
    val d2 = Dog("Doggy", 10)
    val d3 = Dog("White", 10)

    println(d1 == d2)
    println(d2 == d3)
}

8. Instantiate an abstract class:

 abstract class Dog {
    abstract fun bark()
}

val d = object: Dog() {
    override fun bark() {
        println("Bark bark")
    }
}
d.bark()

9. try-catch/if expression:

val y = if (x == 1) {
    "one"
} else if (x == 2) {
    "two"
} else {
    "other"
}