Kotlin Keywords

Keywords are used of special meaning and purpose of programming language. Generally kotlin keywords is dividing of three category. there is hard keyword, soft keywords and modifier keywords. In this post mention examples of those keywords. Like that how to use and what is the role of keywords.

Kotlin Hard Keyword

Hard keyword means that are not used to define identifies name, function name and class name. They are given in belowing list.

as as? break class continue
do else for fun if
in !in interface is !is
null object package return super
this throw true try typealias
val var when while

val and var keyword

val keyword are used to declare constant (immutable) variable in kotlin programming. And var keyword are used to define mutable variable.

//var and val keyword example

fun main(args: Array<String>) {
    
    //Define variables
    val PI : Float = 3.1415f //constant variable
    var age : Int = 21  
    
    //Not allows to modify new value when its already assigned
    //PI = 3.14 
    
     
    age = 22 //Modified var variable value
    
    println("PI :$PI")
    println("age : $age")
}

Output

PI :3.1415
age : 22

fun and return keyword

fun keyword are to define method (function) in kotlin programming. And return keyword are used to return value by function. For example.

//define a function
fun sum(x:Int,y:Int):Int{
    return x+y //return statement
}
fun main(args: Array<String>) {
    println("Sum : ${sum(3,5)}")
}

Output

Sum : 8

if, else keyword

This if-else is a keyword that are used to define conditional statement. if statement expression is based on boolean value. If that expression are produced boolean value true then this block will be execute. Otherwise if exist other if-else block then it will test similar way to other statement. And (else) statement is last block it will work when (if) and (if-else) statement not work.

if(expresion1){
  //logical code
}else if(expression2){
  //logical code
  //group of statements
}else if(expression3){
  //logical code
  //group of statements
}else{
   //else section
}

break keyword

break is a keyword that is create a termination statement of loop. This statement are used inside of for loop, while loop and do-while loop. For example.

fun main(args: Array<String>) {
  
  var totalCandidate:Int=100
  
  for(candidate in 1..totalCandidate){
      if(candidate*3>=30){
         println("Break Time") 
         break;
      }
      println(" Candidate ($candidate)  Time interval: ${candidate*3}")
  }
}

Output

 Candidate (1)  Time interval: 3
 Candidate (2)  Time interval: 6
 Candidate (3)  Time interval: 9
 Candidate (4)  Time interval: 12
 Candidate (5)  Time interval: 15
 Candidate (6)  Time interval: 18
 Candidate (7)  Time interval: 21
 Candidate (8)  Time interval: 24
 Candidate (9)  Time interval: 27
Break Time

class keyword

class keyword is used to define a class in our program.

//define a class
class Connection{
    fun info(){
        println("This is info function of Connection")
    }
}
fun main(args: Array<String>) {
  
    val obj=Connection() //Create object of class
    obj.info() //Execute function
}

Output

This is info function of Connection

continue keyword

This keyword are used to define loop statement, that are change the flow of loop execution.

fun main(args: Array<String>) {
  
    var index:Int =1
    while(index<10){
        index++
        if(index>3 && index<7){
            continue;//continue statement
        }
        println("index : ($index)")   
    }
}

Output

index : (2)
index : (3)
index : (7)
index : (8)
index : (9)
index : (10)

do- while keyword

while keyword is used to define while loop in program. in above example are given this example of while loop. And do-while is used to create do-while loop in our program. The advantage of this loop are it will work at least one time.

fun main(args: Array<String>) {
    var counter:Int =1
    do{
       //loop statements
        println("$counter")
        counter++
    }while(counter<=3)
}

Output

1
2
3

if, else keyword

This is are used to create condition statement. if statement is based on conditional statement. And this expression are produced boolean result and work on boolean value. When expression is produce True result then executes If-block of statements. otherwise executes of else-block.

//series of if..else statement
if(expression1){
    //when expression1 is true
}else if(expression2){
    //when expression2 is true
}
else if(expression3){
    //when expression3 is true
}
else{
  // when no expression1 is true
}

For example

fun main(args: Array<String>) {
  
    val discount:String ="40 % off" 
    
    //series of if..else statement
    if(discount=="20 % off"){
        println("That is 20 % off")
    }else if(discount=="40 % off"){
        
         println("That is 40 % off")
    }
    else if(discount=="60 % off"){
       println("That is 60 % off")
    }
    else{
       println("Else part")
    }
}

Output

That is 40 % off

for,in keyword

This keyword are used to create for loop and this can be used to iterates element of array, collection element and specified range value.


fun main(args: Array<String>) {
  
   val stringData:String ="Kotlin"
    //iterating string element
    for (element in stringData){
        println("$element")
    }
}

Output

K
o
t
l
i
n

Kotlin Soft Keyword

soft keyword is used to define statement and expression. In different context and scenario this can be used by the name of identifiers.

by catch constructor delegate dynamic
field file finally get import
init param property receiver set
setparam where

Kotlin Modifier Keywords

actual abstract annotation companion const
crossinline data enum expect external
final infix inline inner internal
lateinit noinline open operator out
override private protected public reified
sealed suspend tailrec vararg


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