Kotlin

An Introductory Tutorial

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Language Elements

Data Types

Extension Functions

Object Oriented Kotlin

Data Classes

Coroutines

Collections

Kotlin Example Codes

Kotlin Interview Questions

In Kotlin all data types are objects and can be catgorized as one of the following types:



• Numbers: They can be integer types (byte, short, int, long) or of floating point types (float, double). Floating type is denoted by a trailing f at the end.



     
fun main() {
 // Declaring and assiging values to various number data types.
  val intNum: Int = 3                // Integer
  val shortNum: Short = 4000         // short
  val longNum: Long = 13000000000L   // Long
  val byteNum: Byte = 1              // Byte
  val doubleNum: Double = 3.99       // Double
  val floatNum:  Float = 25.34f      // Float
                    
 // Print all declared numbers.
  println("Integer number type value is "+intNum);             
  println("Short number type value is "+shortNum);  
  println("Long number type value is "+longNum);
  println("Byte number type value is "+byteNum);
  println("Double number type value is "+doubleNum);
  println("Float number type value is "+floatNum);
  }

• Characters: This data type is used to store a single character. A character value must be surrounded by single quotes, e.g. 'a', 'b' etc.



    fun main() {
 // Declare and assign letter to character type.
    val letter: Char = 'K'        
  
 // Print declared character.
   println("Character letter is "+letter);
  } 

• Boolean: They can have value of either true or false.



fun main() {
  // Declaring boolean condition and assigning value to it.
   val boolVariable: Boolean = true   
   
   // Printing bioolean value. 
   println("Boolean condition is "+boolVariable);
}

• Array: It is a mutable collection of a fixed number of values, called elements, which can be referred by an index. Kotlin arrays are generally created with functions such as, arrayOf() , intArrayOf(), charArrayOf() etc. Use of arrayOf() is quick and convenient way for any data type, string, integer, etc. Constructor of Array class can also be used to create an array, which takes two parameters (size of array, function which accepts index of an array element).



fun main() {

// Decalre names to some fruits as array.
  val numbers = arrayOf(1, 2, 3, 4)
  
// or as explicit decalration
  val numbers = arrayOf(1, 2, 3, 4)
  
 
// An array can hold mutlple different data types.
  var mixedArray = arrayOf(1.5, "www.zyasin.com/kotlin.html", 50, 'K')
 

// Modify the second element of number array val numbers = arrayOf[1, 2, 3, 4].
  numbers[2] = 7
  
// Or using set() method.
  numbers.set(1,7) 
  
  
// Print the third element of number array [1, 7, 3, 4].
    println(numbers[3])
    
// Or using get() method.
   println(numbers.get(0))
 

// Print the numbers array as [1, 7, 3, 4].
    println(numbers.contentToString())    
    
// Print length of array, val number=  array [1,7,3,4].

    println(numbers.size)

}

• String: It is a sequence of characters. For example, "Kotlin tutorial at www.zyasin.com!". All strings are objects of String class.



 fun main() {
  var text = "Kotlin tuorial at www.zyasin.com/kotlin.html"
  
  println(text[0])  // first element/character
  
  println(text[12]) // 12th element/character
}

Quiz Questions

Can we declare for arary of string elements in Kotlin, as function of type stringArrayOf()?

Consider an array, val numbers = array [1,7,3,4]. What is wrong when we try to use println(numbers[4])?