Basic Syntax of Kotlin with Example listed below
Val and Var
val : This is used to define constant field and final variable. if we define variable with final then we can assign it value again. this is immutable type of variable
var : This is general type of variable. we can change/ assign a new value to it.those are mutable variable.
String
You can define string as
var value : String = ""
//use val for final variable
or
val value : String? = null
//use val for final variable
In first case you can simply assign not null empty string to variable. and second we can assign null value to string by denoting “?” to string. its simply define that string is nullble
val value : String = null //this will show compile time error. as null value can not be assigned to not null type
Boolean
Same as String
For not null type
var bBoolean : Boolean = false
and for nullable
var bBoolean : Boolean? = null
lateinit
lateinit define that we can initialize variable later so it want throw compile time error.
var mArrayist : ArrayList // it will suggest that please initialize the variable
You can modified to this
lateinit var mArrayist : ArrayList; yehh... now you can initialize this later on
Basically in Kotlin there is no need to add “new” in Syntax for initialize
just do
var inArrayist : ArrayList = ArrayList();
Object replaced with Any
If you want to define “Object” varible like in Java, you can ues “Any” instead. In kotlin “Any” is the super class of the all the classes
How to define Function in Kotlin
Function without return type : Unit (Same as “void” in java)
fun printValue(x: Int, y: Int): Unit { print("mulitple of $x with $y is ${x*y}") }
or
fun printValue(x: Int, y: Int){ print("mulitple of $x with $y is ${x*y}") }
Function with return type (Two argument)-
fun Multiplier(x: Int, y: Int): Int { return x * y; }
Inline function
fun Multiple(x:Int,y:Int) = x*y
calling functions
val muliple = Multiplier(5,10); var multipleInline = Multiple(10,50)
Use Of Conditional Expressions
If Else Expression
fun isEven(a: Int): Boolean { if ((a % 2) == 0) return true else return false }
or
inline
fun isEven(a: Int) = ((a % 2) == 0)
How to Check Type Of Class
Like “Instance of” in Java, We can use “is” operator in Kotlin
fun getListLength(mAny: Any): Int? { if (mAny is ArrayList<*>) { return mAny.size } return null }
Inline
fun isInt(x: Any) = x is Int
and for reverse check
fun getListLength(mAny: Any): Int? { if (mAny !is ArrayList<*>) { return null } return mAny.size }
for loop
fun seeForLoop(mAnys: ArrayList) { for (item in alist) { print(item) } for (index in alist.indices) { print("Index || "+alist.get(index)) } }
While loop
fun seeWhileLoop(listStrings: ArrayList) { var indexOflist = 0 while (indexOflist < listStrings.size) { print(listStrings.get(indexOflist)) indexOflist++ } }
When : This is alternative of “switch” in Java
fun whenLoop(mAny: Any) { when(mAny){ is Text -> "This is text" is Int -> "This is integer" is Boolean -> "This is boolean" } }
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