Kotlin Programming: The Big Nerd Ranch Guide, First Edition

Kotlin’s Built-In Types

You have seen variables that are of the String type and variables of the Int type. Kotlin also has types to handle values like true/false, lists of elements, and key-value pairs for defining mappings of elements. Table 2.1 shows many of the commonly used built-in types available in Kotlin:

Table 2.1  Commonly used built-in types

Type	Description	Examples
String	Textual data	"Estragon" "happy meal"
Char	Single character	'X' Unicode character U+0041
Boolean	True/false values	true false
Int	Whole numbers	"Estragon".length 5
Double	Decimal numbers	3.14 2.718
List	Collections of elements	3, 1, 2, 4, 3 "root beer", "club soda", "coke"
Set	Collections ...