A varible refers to a memory allocation that can be store data.

Variables in kotlin can be allow as like java. 

In kotlin we can define varible as var or val keywords. 

A varible defined by val is immutable(can't change the value )
 

val intvar=12;

intvar=13; /* Error: val can not be change */

To define the mutable varibles we will use var keyword.

var intvar=12;

intvar=13;

here we can change the value of intvar

 

In the above line we didn't define the type of variable, we know kotlin is statically typed langugae. it will infer the type of variable from its initialization value.

 In the above line the intvar type will takes as integer.

 If we want to define the type of variable we will write like below

 var intvar:Int =12;

 If we not initialize a variable its mandatory to define the type of varibale

var k // Error : This varibale must either have a Type annonation or be initialized

k="Kotlin"

The above variable declaration throws error. If we not initalize a variblae we must supply the varible Type.

 So that could be like below

var k:String

 k="Kotlin"

 

Data Types

Kotlin has pre-defined data types like other langugaes Int, Double, Boolean, Char etc.

In Kotlin every data type behaves like Object (In java few are Object(String, Integer, Float) types and few are premitive types(int, float, double,...)

 

Numbers

  •  Integers
  •  Byte -8bit
  •  Short - 16bit
  •  Int - 32 bit
  •  Long - 64bit
  •  Float -32 bit
  •  Double - 32 bit
  • val myByte : Byte = 1
  • val myInt :Int = 20
  • val myFloat :Float = 10.0f
  • val myDouble :Double = 10.0

 

Booleans

 Bolean

 val myConditaion = true

Characters

 Character

 val myChar='A'

Strings

 Strings are immutable, that means we cannot modify a String by changing some of its elements

 var myString="Kotlin, New Version"

 We will see the String properties and functions indetails in Strings chapter.

 

Arrays

 Arrays in kotlin can be defined by Array class.

 We can create array object by two ways.

 arrayOf() function  or

 Array() consturctor

 var intArray= arrayOf(1,2,3,4);

 create array with constructor

var consrtArray=Array(5,{i-> "a $i"});

 We will see the Array properties and functions indetails in Arrays chapter.

 

Type Conversions

 Unlike Java, Kotlin doesn't support implicit conversion

 Example int cann't be assigned to long or Double

var myInt=10

var myLong:Long =myInt /* throw Error : Type missmatched required Long found Int.*/

  Kotlin provided few number functions to explicit conversions

  •   toByte()
  •   toShort()
  •   toInt()
  •   toLong()
  •   toFLoat()
  •   toDouble()
  •   toChar()
  •   val myInt = 100
  •   val myLong = myInt.toLong()