Kotlin Variables

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Kotlin Variables

In this section we will learn variables in Kotlin programming language. You will learn how to initialize and use variables in Kotlin programming language.

In this section we will learn variables in Kotlin programming language. You will learn how to initialize and use variables in Kotlin programming language.

Kotlin Variables Example

Learn to create and use variable to store values in Kotlin program. In this tutorial you will learn to declare basic variable types in this programming language and use in the programming.

Kotlin is statically typed language which means that it the type of variable must be declared at the time of compilation. In Kotlin you can define the variable type or leave it without any type. If you leave it without any type declaration then Kotlin will automatically assign a type to it based on the first value stored in the variable.

Kotlin compiler checks the variable type at the compilation time and generates error if it is not able to assign a type to it. Let's learn to define variables in Kotlin.

Here are two ways of declare variable in Kotlin:

	var country = "French"
	val year = 2017

In the above example we are declaring variables using two type of keywords:

var - its variable and its value can be change after first initialization

val - its value can't be changed after first initialization. This is like static final in Java

Declaring String variables

You can define String variable in Kotlin in following ways:

	//String variable declaration
	var name = "Deepak Kumar"

	//String type variable declaration
	var address: String
	address = "Delhi, India"

In the above example we have declared name variable without any type but assigned String value to it. Kotlin will automatically find out this and make name as String variable.

In the second line with declared address variable with type String. So, these are two ways to declare String variables in Kotlin.

In Kotlin you can't define a variable without type annotation or initialization. For example see following declaration:

var place
place="Delhi"

Above declaration is not valid and compiler will throw error "This variable must either have a type annotation or be initialized".

Kotlin Basic Type

Just like Java Kotlin is strongly type programming language and its is required to provide type of variable at compile time. In Kotin data types can be grouped into:

  • Numbers
  • Characters
  • Booleans
  • Arrays

Number types in Kotlin

In Kotlin Number types are similar to Java numbers and these are:

  1. Byte
  2. Short
  3. Int
  4. Long
  5. Float
  6. Double

Byte Types

Following is example of declaration of Byte type variables:

//Byte Types
var var1: Byte =  100
println(var1)

Short Types

Example of declaring short type variables.

//Short Types
var var2: Short =  100
println(var2)		

Int Types

Example of Int Type declaration in Kotlin:

//Int type
var var3: Int =  100
println(var3)

Long Types

Here is example of declaration of Long type variables in Kotlin:

//Long Types
var var4: Long =  100
println(var4)

Float Types

Here is example of defining Float variables in Kotlin programming language:

//Float Types
var var5: Float =  10.0f
println(var5)

Double Types

Example of creating Double type variable in Kotlin:

//Double Types
var var6: Double =  12.0
println(var6)

Declaring Char variables

In the following we are declaring a Char type variable:

val letter: Char
letter = 'A'
println("$letter")

Boolean variables in Kotlin

In programming language there are two values of boolean, true or false. In Kotlin concept is the same and it can defined in following ways:

//Boolean variable
var flag = true
println("$flag")

Arrays in Kotlin

Like Java it also supports arrays of different types. Here is an example of declaration of in type array:

//Int arrays
val numbers: IntArray = intArrayOf(1, 2, 3, 4, 5)

Here is complete example of declaring different types of variables in Kotlin:

package net.roseindia
import java.util.*

fun main(args: Array) {
	println("Hello, World!")

	//Variable
	var country = "French"
	//Non mutable variable - Value can't be changed
	val year = 2017

	//String variable declaration
	var name = "Deepak Kumar"

	//String type variable declaration
	var address: String
	address = "Delhi, India"

	var place="Delhi"



	//Byte Type
	var var1: Byte =  100
	println(var1)

	//Short Type
	var var2: Short =  100
	println(var2)
			
	//Int type
	var var3: Int =  100
	println(var3)
				
	//Long Types
	var var4: Long =  100
	println(var4)

	//Float Types
	var var5: Float =  10.0f
	println(var5)

	//Double Types
	var var6: Double =  12.0
	println(var6)

	//Char variable
	var letter: Char
	letter = 'A'
	println("$letter")

	//Boolean variable
	var flag = true
	println("$flag")
					
	//Int arrays
	val numbers: IntArray = intArrayOf(1, 2, 3, 4, 5)
		

}

You can run this program in Eclipse and see the output.

In this tutorial you learned to declare and use basic data types in Kotlin

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