Kotlin Variables
Variables are containers for storing data values.
- To create a variable, use var or val, and assign a value to it with the equal sign (=)
- The difference between var and val is that variables declared with the var keyword can be changed/modified, while val variables cannot.
Variable types: Unlike many other programming languages, variables in Kotlin do not need to be declared with a specified type (like "String" for text or "Int" for numbers, if you are familiar with those).
var name = "John" // String (text)
val birthyear = 1992 // Int (number)
Kotlin is smart enough to understand that "John" is a String (text), and that 1992 is an Int (number) variable.
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You can also declare a variable without assigning the value, and assign the value later. However, this is only possible when you specify the type:
var name: String
name = "John"
println(name)
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So When To Use val?
The val keyword is useful when you want a variable to always store the same value, like PI (3.14159...)
- Variable Names can have a short name (like x and y) or more descriptive names (age, sum, totalVolume).
- Names can contain letters, digits, underscores, and dollar signs
- Names should start with a letter
- Names can also begin with $ and _ (but we will not use it in this tutorial)
- Names are case sensitive ("myVar" and "myvar" are different variables)
- Names should start with a lowercase letter and it cannot contain whitespace
- Reserved words (like Kotlin keywords, such as var or String) cannot be used as names
- CamelCase variables
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