Mutable Variables
A mutable variable is declared with the var keyword and represents a value that is expected to change throughout a program.
var age = 25
age = 26
Immutable Variables
An immutable variable is declared with the val keyword and represents a value that must remain constant throughout a program.
val goldenRatio = 1.618Type Inference
When a data type is not specified in a variable declaration, the variable’s data type can be inferred through type inference.
// The following variable is assigned a text value within double quotes, thus the inferred type is String
var color = "Purple" String Concatenation
String concatenation is the process of combining Strings using the + operator.
var streetAddress = "123 Main St."
var cityState = "Brooklyn, NY"
println(streetAddress + " " + cityState)
// Prints: 123 Main St. Brooklyn, NY
String Templates
String templates contain String values along with variables or expressions preceded by a $ symbol.
var address = "123 Main St. Brooklyn, NY"
println("The address is $address")
// Prints: The address is 123 Main St. Brooklyn, NYBuilt-in Properties and Functions
The Kotlin String and Character data types contain various built-in properties and functions. The length property returns the number of characters in a String, and the capitalize() function capitalizes the first letter of a String.
var monument = "the Statue of Liberty"
println(monument.capitalize()) // Prints: The Statue of Liberty
println(monument.length) // Prints: 21Character Escape Sequences
Character escape sequences consist of a backslash and character and are used to format text.
\nInserts a new line\tInserts a tab\rInserts a carriage return\'Inserts a single quote\"Inserts a double quote\\Inserts a backslash\$Inserts the dollar symbol
print("\"Excellent!\" I cried. \"Elementary,\" said he.")
// Prints: "Excellent!" I cried. "Elementary," said he. Arithmetic Operators
The arithmetic operators supported in Kotlin include + addition, - subtraction, * multiplication, / division, and % modulus.
5 + 7 // 12
9 - 2 // 7
8 * 4 // 32
25 / 5 // 5
31 % 2 // 1 Order of Operations
The order of operations for compound arithmetic expressions is as follows:
- Parentheses
- Multiplication
- Division
- Modulus
- Addition
- Subtraction
When an expression contains operations such as multiplication and division or addition and subtraction side by side, the compiler will evaluate the expression in a left to right order.
5 + 8 * 2 / 4 - 3 // 6
3 + (4 + 4) / 2 // 7
4 * 2 + 1 * 7 // 15
3 + 18 / 2 * 1 // 12
6 - 3 % 2 + 2 // 7 Augmented Assignment Operators
An augmented assignment operator includes a single arithmetic and assignment operator used to calculate and reassign a value in one step.
var batteryPercentage = 80
// Long Syntax
batteryPercentage = batteryPercantage + 10
// Short Syntax with an Augmented Assignment Operator
batteryPercentage += 10 Increment and Decrement Operators
Increment and decrement operators provide a shorthand syntax for adding or subtracting 1 from a value. An increment operator consists of two consecutive plus symbols, ++, meanwhile a decrement operator consists of two consecutive minus symbols, --.
var year = 2019
year++ // 2020
year-- // 2019 The Math Library
The Math library, inherited from Java, contains various mathematical functions that can be used within a Kotlin program.
Math.pow(2.0, 3.0) // 8.0
Math.min(6, 9) // 6
Math.max(10, 12) // 12
Math.round(13.7) // 14