Declaration rules for Kotlin.
typealias EmployeeSet = Set<Employee> // Declare at top of class
val MY_CONSTANT = 100 // Constants can be declared at the top-level in Kotlin
fun main() {
val number: Short = 25 // Force a Float as the default would be Int
// number = "heya" // Cannot change variable type
// USE VAL UNLESS YOU NEED VARIABLE TO BE REASSIGNED
val number2: Int // val can be declared without be initialised
number2 = 25 // so now it's happy
// number2 = 22 // val cannot be reassigned once initialised
var number3: Int // var can be declared without be initialised
number3 = 25
number3 = 22 // var can be reassigned once initialised
val employee1 = Employee("Lynn Jones", 500) // employee1 is fixed, cannot be reassigned
employee1.name = "Lynn Smith" // However, var properties within a val can be reassigned
val employee2: Employee
val number4 = 100
if (number < number4) {
employee2 = Employee("Jane Smith", 400)
} else {
employee2 = Employee("Mike Watson", 150)
} // Might look iffy but is still acceptable because employee2 will only be assigned once
val sb: StringBuilder // <- Check declaration to see that StringBuilder is a Type Alias: @SinceKotlin("1.1") public actual typealias StringBuilder = java.lang.StringBuilder See top of class
val employees: EmployeeSet // Example of type alias declared at start of class
val names = listOf("John", "Jane", "Mary")
println(names[1]) // Use square brackets to access Collection members
for (i in 1..5) {
println(i)
}
println(employee1)
val change = 4.22
println()
println("$$change")
println("To prevent the variable being printed out escape using \$change")
val numerator = 10.99
val denominator = 20.00
println("The value of $numerator divided by $denominator is ${numerator/denominator}")
println("Employee ID is ${employee1.id}") // References to other class properties are considered expressions so put them in brackets
val filePath = "c:\\dir\\somedir" // Regular strings can sometimes require a lot of escapes
val filePath2 = """c:\dir\somedir""" // No need for escapes with triple quoted strings!
println()
val nurseryRhyme = """Humpty Dumpty sat on a wall
Humpty Dumpty had a great fall
All the king's horses and all the king's men
Couldn't put Humpty together again"""
println(nurseryRhyme)
println()
val nurseryRhyme2 = """Humpty Dumpty sat on a wall
*Humpty Dumpty had a great fall
*All the king's horses and all the king's men
*Couldn't put Humpty together again""".trimMargin("*") // Trims everything before the quoted character. Means we can use margins in code. Default character is |
println(nurseryRhyme2)
println()
val eggName = "Humpty"
val nurseryRhyme3 = """$eggName Dumpty sat on a wall
|$eggName Dumpty had a great fall
|All the king's horses and all the king's men
|Couldn't put $eggName together again""".trimMargin() // Trims everything before the quoted character. Means we can use margins in code. Default character is |
println(nurseryRhyme3)
println()
println(MY_CONSTANT) // Printing top-level constant from within class
}
class Employee(var name: String, val id: Int) {
override fun toString(): String {
return "Employee(name='$name', id=$id)"
}
}