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
:
In total, Kotlin has the following basic types:
Category | Basic types |
---|---|
Integers |
|
Unsigned integers |
|
Floating-point numbers |
|
Booleans |
|
Characters |
|
Strings |
|
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:
Now that you know how to declare basic types, it's time to learn about collections.
Practice
Exercise
Explicitly declare the correct type for each variable: