Kotlin what_you_need_to_know-converted event 4 with nigerians

Kotlin: What you
need to know
Android Development with Kotlin v1.0 ThisThis workwork isislicensedlicensed underunder thethe
ApacheApache 2
2licenselicense.. 1
1
1
Umar SaiduAuna
Software Engineer, gidimo
tech community Organizer
umarauna
November 24, 2021

What mostly happen to JAVA programmers before Kotlin

History
Kotlin is a cross-platform, statically typed, general-purpose
programming language and runs on the JVM

History
Kotlin is a cross-platform, statically typed, general-purpose
programming language and runs on the JVM.
Kotlin was developed by JetBrains (Makers of IntelliJ)

History
Kotlin is a cross-platform, statically typed, general-purpose programming language and
runs on the JVM.
Kotlin was developed by JetBrains (Makers of IntelliJ)
First commit dates back to 2010, but was first publicly seen around 2011.

History - Why did Google make it official?
Awesome features - nullable types, concise, data classes, etc.
Great community support
There was an overwhelming request for Kotlin
official support on Android

What is Kotlin
Kotlin is a cross-platform, statically typed, general-purpose programming
language, it is also JVM based language developed by JetBrains as
described before, a company known for the creation of IntelliJ IDEA, a
powerful IDE for Java development. In Kotlin everything is an Object.

What is Kotlin
Kotlin is very intuitive and easy to learn for Java developers
(give it 10 days trials and you wont regret).

What is Kotlin
Its more expressive & safer

What is Kotlin
Its more expressive & safer
Its highly interoperable

“In Kotlin, everything is an object
(reference type), we don’t find primitives
types as the ones we can use in
Java……...”

implemeantation 'com.github.UmarAuna:Carousels-Kotlin:0.0.2'
http://bit.ly/kotlin-image-carousel

Kotlin sample code…..
fun main(args: Array<String>){
//your code goes here
}

Kotlin 1.3 no more (args: Array<String>)
fun main(){
// your code goes here
}

Null Safety - nullable types and non-nullable types
Tony Hoare, one of the creators of the programming language ALGOL.
Protects against NullPointerException the $1,000,000,000 mistake

A non-nullable object can’t be null
// compiler error
var name: String
name = null

A non-nullable object can’t be null
// compiler error
var name: String
name = null
Specify a nullable object by using “?”
// compiler error
var name: String?
val length = name.length Kotlin ensures that you don’t mistakenly operate on nullable objects

Null Safety - Accessing properties in a nullable object
1. Checking for null types
// handle non-null case and null case
var name: String? = null
val length = if (name != null) name.length else 0

2. Making safe calls using “?.”
//use ?. to make safe call
var name: String?
...
val length = name?.length
Use ?. to safely access a property/method on a
nullable object
If name happens to be null, the value of length is 0
(inferred integer).
length would be null if it were of another type.

3. Making use of the “?:” elvis operator
//use elvis operator
var name: String?
val length = name?.length ?: 0
This reads as “if name is not null, use
name.length else use 0
Elvis Presley. His hairstyle resembles a Question Mark

4. Making use of the “!!” assertion operator
//use assertion operator
val length = name!!.length
name.length else throw a null pointer
exception”

4. Making use of the “!!” assertion operator
//use elvis operator
val length = name!!.length
name.length else throw a null pointer
exception”
Be very careful with this operator!!!

Null Safety - NPE free!
You can only have the NullPointerException in Kotlin if:
1. You explicitly throw a NPE
2. You make use of the !! operator
3. An external Java code causes the NPE.

String Interpolation / template in Kotlin
fun hello(name: String) {
println("Hello, $name")
}

String Interpolation in Java + Kotlin
void hello(String name) {
System.out.println("Hello, " + name);
}

Immutability
Kotlin helps developers to be intentional about immutability.
Immutability simply means that things you create can’t be changed.
We need immutability because it:
● helps us with thread safety - no synchronization issues
● is good for value objects - objects that simply hold value, POJOs etc.
● helps debugging threaded applications without losing your hair

Immutability
How does it work in Java?
●Immutability in Java?
final classes
private fields
no setters
● Immutability in Kotlin? Guess?

Immutability
How does Kotlin help?
var vs val
// compiler error: val cannot be reassigned
val name = "Umar"
name = name.toUpperCase()
// works fine
var name = "Umar"
name = name.toUpperCase()

Immutability
How does Kotlin help?
Immutable and Mutable collections
// immutable collection
val unchangeableHobbies = listOf("coding", "hiking")
unchangeableHobbies.add() // add method doesn’t exist
// mutable collection
val changeableHobbies = mutableListOf("reading", "running")
changeableHobbies.add("travelling") // you can add

Immutability
In Java vs Kotlin
public final class ImmutableClassJava {
private final String name;
private final int age;
public ImmutableClassJava(String name, int age) {
this.name = name;
this.age = age;
}
// no setters
public String getName() {
return name;
}
public int getAge() {
return age;
}
}
class ImmutableClassJava(val name: String, val age: Int)
● Class is final by default
●val implies that the parameters are
final as well (values can’t be assigned)

Functions
// function sample
fun sampleFunc() {
// code goes here
}
A function is declared using the “fun”
keyword

Functions
// function sample
fun sampleFunc() {
// code goes here
}
// function with param
fun sampleFuncWithParam(param: String) {
// code goes here
}
keyword
Method parameters use the “name:Type”
notation

Functions
// function sample
fun sampleFunc() {
// code goes here
}
// function with param
fun sampleFuncWithParam(param: String) {
// code goes here
}
// func with param and return type
fun capitalize(param: String): String {
return param.toUpperCase()
}
keyword
Method parameters use the “name:Type”
notation
Return types are specified after the
method definition.

Functions - infix functions
// infix function
infix fun Int.times(x: Int): Int {
return this * x
}
We can use the function as an arithmetic operator, i.e.,
using it without writing dots and parentheses.

Functions - infix functions
// infix function
infix fun Int.times(x: Int): Int {
return this * x
}
// usage
fun useInfix() {
val product = 2 times 5
println(product)
}
We can use the function as an arithmetic operator, i.e.,
using it without writing dots and parentheses.

Functions - extension functions
// extension function
fun Int.square(): Int {
return this * this
}
Extension function is a member function of a class that is
defined outside the class

Functions - extension functions
// extension function
fun Int.square(): Int {
return this * this
}
Extension function is a member function of a class that is
defined outside the class
// usage
fun useExtension() {
val square = 2.square()
println(square)
}

Functions
Others:
● Higher order functions
● Lambdas
● Inline functions etc.

Conciseness in Kotlin
public void doSomething() {
// do something
}
fun doSomething(): Unit {
// do same thing
}

public void doSomething() {
// do something
}
fun doSomething() {
// do same thing
}

return name;
}
fun getName(): String {
return name
}

return name;
}
fun getName() {
return name
}

return name;
}
fun getName() = name

Class in Java vs Data Class in Kotlin
public class Person {
private String name;
String getName () {
return name;
}
void setName (String name) {
this.name = name;
}
@Override
public String toString () {
return "Person{" +
"name='" + name + ''' +
'}';
}
}
data class Person(val name: String)

Class in Java vs Regular Class in Kotlin
String getName () {
return name;
}
this.name = name;
}
public int getNameLength () {
return name.length
}
}
class Person(name: String) {
var name: String
get() = name
set(name) {
this.name = name
}
fun getNameLength(): Int {
return name.length
}
}

Class in Java vs Regular Class in Kotlin
String getName () {
return name;
}
this.name = name;
}
public int getNameLength () {
return name.length
}
}
class Person(name: String) {
var name: String
get() = name
set(name) {
this.name = name
}
fun getNameLength() = name.length
}

Important place to learn…….

Tutorials Point - Kotlin

Kotlin for Android Developers – Antonio Leiva

Koans online – try.kotl.in/koans

Kotlin Bootcamp for Programmers - Udacity

Kotlin Bootcamp for Programmers - Udacity
https://developer.android.com/kotlin/learn

Stay updated…….
Kotlin Weekly
http://www.kotlinweekly.net/
Kotlin Conf
kotlinconf.com

Summary
• Interoperable with Java (100%)
• Reduces Boilerplate code
• Object-Oriented and procedural
• Safety code
• No Semicolon
• Expands your skillset
• Perfect Support with Android Studio & Gradle
• Very easy to get started with Android Development

Reduces Boilerplates codes like:
findViewById, Async, build interfaces
with Kotlin code etc

Kotlin Android Extension it includes a view
binder. The plugin automatically creates a set
of properties that give direct access to all the
views in the XML.

Finally
You have 3 Options..
1
Decide Kotlin is not
For you and continue
with Java

Finally
1
with Java
2
Try to learn
everything
on your own

Finally
1
with Java
3
Go and learn on
MOOC websites
2
Try to learn
everything
on your own

Questions
? Thank
you!
Android Development with Kotlin v1.0 ThisThis workwork isislicensedlicensed underunder thethe
ApacheApache 2
2licenselicense.. 878787
Umar SaiduAuna
Software Engineer, gidimo
tech community Organizer
umarauna

A PROGRAMMING
LANGUAGE THAT BRINGS JOY
TO PROGRAMMERS
INTRODUCTION TO
KOTLIN

SOFTWARE DEVELOPER
AND TRAINER
ABO
UT
ME
• Android and IOS Developer.
• Lead Mobile Developer for DOUBLET (App For
Couples).
• Project Lead and Lead Mobile
Developer for KITCHLY (App for Food
Lovers).
• Software Trainer at Rework Academy.
CONNECT: linkedin.com/in/young-batimehin-
5a6208159
YOUNG AYODEJI BATIMEHIN

LET’s GET TO
KNOW THE
AUDIENCE

1) Introduction to
Kotlin
2) Features
3) Kotlin Vs Java
4) Set Up Development Environment
5) Build a List App.
6) Conclusion and Questions.
Today’s
Agenda

• Kotlin is a statically typed programming language.
• It supports object-oriented programming and functional programming
features.
• It can also be compiled into Javascript source code.
• Extension of the Kotlin is (.kt)
• It’s a JVM targeted language.
• Kotlin supports procedural programming with the use of functions.
• Supports Multi-platform projects.
• It is an open-source language.
• It is now the official language for Android Development.
INTRODUCTIO
N
KOTLIN

FEATURES
Use Kotlin for any
type of Enterprise
Java EE
Development
100 %
Compactible
with all JVM
frameworks
Null Safety. Kotlin
Avoids the null
pointer exception
when using or
declaring variables.
Kotlin wants you
to write less
code
Familiar to Java.
But you can still
learn Kotlin
without
experience with
java
Automatic
Conversion from
Kotlin to java
Strong
Community
Kotlin integrates well
with all existing Java
Frameworks and
Libaries

• Open Android Studio
• Set-up Android project with Kotlin as code base
• Brief explanation of all dependency and
implementation
• Implement Recycler View
• Implement Cardview
• Use Custom RecyclerView Adapter
• Model Class
• Layout Managers
Set Up Development
Environment
FOR LIST APP

Kotlin what_you_need_to_know-converted event 4 with nigerians

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