Get Started with Kotlin on Android

In this blog, we’re going to take a look at Kotlin, a new language in the JVM world, and some of its basic features, including classes, inheritance, conditional statements, and looping constructs.

Defining function in kotlin

fun sum(a: Int, b: Int): Int {
    return a + b
}

//Function with an expression body and inferred return type

fun sum(a: Int, b: Int)=a+b

fun sum(a: Int, b: Int): Int {

return a + b

}

//Function with an expression body and inferred return type

fun sum(a: Int, b: Int)=a+b

Defining variables

val a: Int = 1  // immediate assignment
val b = 2   // `Int` type is inferred
val c: Int  // Type required when no initializer is provided
c = 3       // deferred assignment

val a: Int = 1 // immediate assignment

val b = 2 // `Int` type is inferred

val c: Int // Type required when no initializer is provided

c = 3 // deferred assignment

Using when expression it’s more like switch case.

when(a){
 1->fun sum(a: Int, b: Int)= a+b

 2->fun sub(a: Int, b: Int)=a-b 

  else-> a 

}

when(a){

1->fun sum(a: Int, b: Int)= a+b

2->fun sub(a: Int, b: Int)=a-b

else-> a

}

Using a for loop

val items = listOf("apple", "banana", "kiwi")

for (item in items) {
    println(item)
}

// While loop
val items = listOf("apple", "banana", "kiwi")
var index = 0
while (index < items.size) {
    println("item at $index is ${items[index]}")
    index++
}

val items = listOf("apple", "banana", "kiwi")

for (item in items) {

println(item)

}

// While loop

val items = listOf("apple", "banana", "kiwi")

var index = 0

while (index < items.size) {

println("item at $index is ${items[index]}")

index++

}

Constructors

A class in Kotlin can have a primary constructor and one or more secondary constructors. The primary constructor is part of the class header it goes after the class name (and optional type parameters).

class Person constructor(firstName: String) {
}

// Secondary Constructor
class Person {
    constructor(parent: Person) {
        parent.children.add(this)
    }
}

class Person constructor(firstName: String) {

}

// Secondary Constructor

class Person {

constructor(parent: Person) {

parent.children.add(this)

}

Have you notice there no semicolon in sentences in Kotlin you don’t have to put the semicolon at the end of sentences. Null-safety is an important feature of the Kotlin language. It helps developers avoid NullPointerExceptions and improves the quality of their apps.

manish choudhary 6 November 2017

. . .

Get Started with Kotlin on Android

Defining function in kotlin

Defining variables

Using when expression it’s more like switch case.

Using a for loop

Constructors

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