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Written by: developervsandhu

Technology and Gadgets

Kotlin Control Statements

Control Statments

if

In Kotlin, if is an expression is which returns a value. It is used for control the flow of program structure. There is various type of if expression in Kotlin.


    if(condation){
    //code statement
    }

    // Syntax of traditional if else statement

    if(condation){
    //code statement
    }
    else{
    //code statement
    }

    // Kotlin if-else Expression

    val returnValue = if (condation) {
    //code statement
    } else {
    // code statement
    }
    println(returnValue)

    //

    // Ladder if example

    val grade: Char = if (marks in 91..100) {
        'A'
    } else if (marks in 81..90) {
        'B'
    } else if (marks in 71..80) {
        'B'
    } else {
        'F'
    }

When Expression

Kotlin, when expression is a conditional expression which returns the value. Kotlin, when expression is replacement of switch statement. Kotlin, when expression works as a switch statement of other language (Java, C++, C).

 val grade: Char = when (marks) {
        in 91..100 -> 'A'
        in 81..90 -> 'B'
        in 71..80 -> {
            println("testing")
            'C'
        }

        else -> {
            'F'
        }
    }


    println("Grade is $grade")

Programms

Loops

Repeat the statements n number of times

While

Alt text

    var count = 1
    while (count <= 10)
    {
        // body statements
        println("durgesh $count")
        count++
    }

    println("Loop exited")

Do..While

Alt text

    var count = 1
    do {
        println("durgesh $count")
        count++
    } while (count <= 10);

For loop


    for (i in 10 downTo 1) {
        println(i)
    }

    for (i in 0..100 step 3) {
        println(i)
    }

    for (i in 1 ..9) {
        println("i = $i")
    }

     val favActivities: Array<String> = arrayOf("cricket", "chess", "music", "programming")
    for (activity in favActivities.reversed()) {
        println(activity)
    }

Watch First part

https://www.youtube.com/watch?v=1-LLZEGDOIc

Operators

Operators are the special symbols used to perform operations. eg +,-,>..

Arithmetic Operators

Perform methametical operations

| Operator | Example | Explanation | | -------- | ------- | ---------------- | | + | a+b | add two operands | | - | a-b | substract | | * | a*b | multiply | | / | a/b | Divide | | % | a%b | Modulus | | ++ | a++ | Increment | | -- | a-- | Decrement |
Assigment Operators

Assigns value to variable.

val a=5;

where = is assignment operator

We can use assignment and arthemetic operators togetter togetter the called Arithemetic Assignment Operators

| Operator | Example | Expansion | Explanation | | -------- | ------- | --------- | --------------------------------------- | | += | a+=b | a=a+b | Add a to b and then assign to a | | -= | a-=b | a=a-b | Substract b from a and then assign to a |

etc..

Comparison Operators

Compare two values

| Operator | Example | Explanation | | -------- | ------- | ------------------ | | == | a==b | Equal | | < | a<b | Less than | | > | a>b | Greater than | | <= | a<=b | Less than equal | | >= | a>=b | Greater than equal | | != | != | Not equal |
Logical Operators

Determain logic between to values

| Operator | Example | Explanation | | -------- | -------------------------- | --------------------------------------------- | | && | condition1 && condition2 | return true if both condition are true | | || | condition1 || condition2 | return true if any of two conditions are true | | ! | !a | reverse the result |

Hard Keywords

is used for type casts.

  val ob: Any ="Testing"
  val test=ob as String

specifies an alias for an import

import java.util.ArrayList as SubstringList

in

specifies the object being iterated in a for loop.
```
for(i in 1..10)
{

}
```
is used as an infix operator to check that a value belongs to a range, a collection, or another entity that defines a 'contains' method.
```
if(i in  collection)
{

}
```

is used in when expressions for the same purpose.

marks a type parameter as contravariant.

   interface Demo<in T>
    {
        // T is only consumed never produced
    }

is

checks that a value has a certain type.

is used in when expressions for the same purpose.
typealias

for type aliasing
```
typealias DkSet = Set<String>
```
Do read : https://kotlinlang.org/docs/keyword-reference.html

Smart Typecasting( Smart Cast )

Kotlin convert types automatically if itcheck the type with is keyword in if condition.


fun test(value: Any) {

    if (value is String) {
        print(value.length)
    } else {
        print(value)
    }

}

Functions in Kotlin

Set of statements written for doing a specific task.

Function has name, return type , parameters and modifiers.

how to define function in kotlin

fun keyword is used to defined function in kotlin

fun [functionName] ([parameter]) : [retunType]
{

//body of the  function

return [Value]

}


//example

fun myFun(n1:Int, n2:Int):Int
{
    return n1+n2
}

using the functions

Function can be used when we call the function

val result=myFun(2,5)

Default Argument

fun myFun(
    b: ByteArray,
    off: Int = 0,
    len: Int = b.size,
) { /*...*/ }

Name argument

We can use name when calling

myFun(

off=4,
b=arr,
len=45

)

Lambda

Kotlin functions are the first class which means they can be stored in variables , passed as an argument , returned from another functions .

The function that takes another function as parameter or return another function is called Higher order functions.

fun highOrder(value: () -> Unit, intValue: Int): () -> Unit {

    value()

    return value
}

Kotlin Control Statements