In this lesson, we will consider the classification and properties of the basic types provided by Kotlin. Maybe you already know a few of them. The basic types can be separated into several groups according to meaning. Types from the same group can be operated in the same way, but have different sizes and, as consequence, represent different ranges of values.
You do not need to know all this information by heart, because it is easy to find it in the documentation or simply Google it. But a common understanding of these concepts is important in job interviews and practice.
Note, the name of a type always starts with an uppercase letter.
Numbers
Kotlin provides several types for integers and fractional numbers.
Integer numbers (0, 1, 2, ...) are represented by the following four types:Long, Int, Short, Byte (from the largest to the smallest). These types have different sizes and may represent different ranges of values. The range of an integer type is calculated as −(2n−1) to (2n−1)−1, where n is the number of bits. The range includes 0, which is the reason for subtracting 1 from the upper bound.Byte: size 8 bits (1 byte), range from -128 to 127Short: size 16 bits (2 bytes), range from -32768 to 32767Int: size 32 bits (4 bytes), range from −(231) to (231)−1Long: size 64 bits (8 bytes), range from −(263) to (263)−1
The sizes of types are always the same. They do not depend on the operating system or hardware and cannot be changed.
The most commonly used integer types are Int and Long. Always try to use Int if it is enough for your purposes. Otherwise, use Long.
val zero = 0 // Int
val one = 1 // Int
val oneMillion = 1_000_000 // Int
val twoMillion = 2_000_000L // Long, because it is tagged with L
val bigNumber = 1_000_000_000_000_000 // Long, Kotlin automatically choose it (Int is too small)
val ten: Long // Long, because the type is specified
val shortNumber: Short = 15 // Short, because the type is specified
val byteNumber: Byte = 15 // Byte, because the type is specifiedFloating-point types represent numbers with fractional parts. Kotlin has two such types: Double (64 bits) and Float (32 bits). These types can store only a limited number of significant decimal digits (~6-7 for Float and ~14-16 for Double). Usually, you will use the Double type in practice.
val pi = 3.1415 // Double
val e = 2.71828f // Float, because it is tagged with f
val fraction: Float = 1.51 // Float, because the type is specifiedNote: To display the maximum and minimum value of a numeric type (including Double and Float), you need to write the type name followed by a dot and then either one of MIN_VALUE or MAX_VALUE.
println(Int.MIN_VALUE) // -2147483648
println(Int.MAX_VALUE) // 2147483647
println(Long.MIN_VALUE) // -9223372036854775808
println(Long.MAX_VALUE) // 9223372036854775807Characters
Kotlin has a type named Char to represent letters (uppercase and lowercase), digits, and other symbols. Each character is just a single letter enclosed in single quotes. This type has the same size as the Short type (2 bytes = 16 bits).
val lowerCaseLetter = 'a'
val upperCaseLetter = 'Q'
val number = '1'
val space = ' '
val dollar = '$'Characters can represent symbols from many alphabets including hieroglyphs, as well as some special symbols which will be studied in the following lessons.
Booleans
Kotlin provides a type called Boolean, which can store only two values: true and false. It represents only one bit of information, but its size is not precisely defined.
val enabled = true
val bugFound = falseWe will often use this type in conditionals and as a result of comparing two numbers.
Strings
String type represents a sequence of characters enclosed in double quotes. Actually, it is one of the most used types.val creditCardNumber = "1234 5678 9012 3456"
val message = "Learn Kotlin instead of Java."String, Int, Long, Boolean, Char, and Double. Other data types will be studied later on. Remember that Long is the largest integer type. Knowledge of the sizes and ranges of integer types may help you in job interviews.