Basic types

Every variable and data structure in Kotlin has a data type. Data types are important because they tell the compiler what you are allowed to do with that variable or data structure. In other words, what functions and properties it has.

In the last chapter, Kotlin was able to tell in the previous example that customers has type: Int. Kotlin's ability to infer the data type is called type inference. customers is assigned an integer value. From this, Kotlin infers that customers has numerical data type: Int. As a result, the compiler knows that you can perform arithmetic operations with customers:

xxxxxxxxxx

var customers = 10

​

// Some customers leave the queue

customers = 8

​

customers = customers + 3 // Example of addition: 11

customers += 7            // Example of addition: 18

customers -= 3            // Example of subtraction: 15

customers *= 2            // Example of multiplication: 30

customers /= 3            // Example of division: 10

​

println(customers) // 10

tip

+=, -=, *=, /=, and %= are augmented assignment operators. For more information, see Augmented assignments.

In total, Kotlin has the following basic types:

For more information on basic types and their properties, see Basic types.

With this knowledge, you can declare variables and initialize them later. Kotlin can manage this as long as variables are initialized before the first read.

To declare a variable without initializing it, specify its type with :.

For example:

xxxxxxxxxx

// Variable declared without initialization

val d: Int

// Variable initialized

d = 3

​

// Variable explicitly typed and initialized

val e: String = "hello"

​

// Variables can be read because they have been initialized

println(d) // 3

println(e) // hello

Now that you know how to declare basic types, it's time to learn about collections.

xxxxxxxxxx

fun main() {

    val a = 1000

    val b = "log message"

    val c = 3.14

    val d = 100_000_000_000_000

    val e = false

    val f = '\n'

}

Example solution
 {...}