The document provides information about Kotlin, including that it is 100% interoperable with Java, was developed by JetBrains, and reached 1.0 release status in 2016. Some key benefits of Kotlin are that it is concise, safe, functional, and can reduce the amount of boilerplate code needed. Kotlin code is also null-safe to avoid null pointer exceptions. It allows Java and Kotlin code to coexist and is an increasingly popular language for Android development.

1. Version: Jan 10, 2019

2. 2
KOTLIN
100 % interoperable with java
Developed By Jet Brains.

3. 3
HISTORY
2010 – Work Started
2011 – Announced
2016 – 1.0 Released
2017 – 1.1 Released
 In Google I/O 2017 they announced that First-class support for Kotlin.
 Android Studio 3.0 is released and Kotlin is by default supported. No other
setup required.
 Kotlin is a growing community and it is also acknowledged by Google.

4. 4
 Null references are controlled by the system.(NPE)
 No raw types.
 Kotlin does not have checked Exceptions.
 Requires more code to do simple tasks.
 Not that friendly with android.
 Inability to add methods in platform APIs, have to use Utils for that.
 For Android ,it’s nullability everywhere

5. 5
WHY KOTLIN?
Kotlin & Java
can exist
together in one
project. You
can keep on
utilizing
existing
libraries in
Java
Concise Safe It's functional
Kotlin & Java
can exist
together in one
project. You
can keep on
utilizing
existing
libraries in
Java
Definitely
reduce the
measure of
standard code
you have to
compose
Avoid entire
classes of
errors such as
null pointer
exceptions
Kotlin utilizes
numerous
ideas from
functional
programming,
for example,
lambda
expressions
100% interoperable with Java
Source: google.com

6. 6
KEY BENEFITS OF ADOPTING KOTLIN
Open
Source
Kotlin Offers
Shortness
Mature
Language
With a Great
IDE Support
Provides an Easier
Way to Develop
AndroidApps
Swift Language
forAndroidApp
Development
Reliable Due
to its
Evolutionary
Process
Much Safer
Than Java
Easy to
Learn
Runs on
JVM
Combines
OO and
Functional
Programin
g
Saves30 - 40%
lines of code
Source: google.com

7. 7
Declaring a variable
 var - Mutable variable
 val – Immutable or final viable
Example:
val name:String=“Pocket Office”// immutable or final
var name:String=“Pocket Office” // mutable
Ex. name=“NCR”
val name=“Pocket Office” // Types are auto-inferred
val num:Int=10// immediate assignment
var personList:List<String>()=ArrayList()
Statically Type
In java : final String name=“Pocket Office”;
In Kotlin: val name=“Pocket Office”
 Double
 Float
 Long
 Int
 Short
 Boolean
 Char
 String
 Array
Basic Data Types

8. 8
Saving time with Kotlin
#1. Static Layout Import
One of the most common boilerplate codes in Android is using the findViewById() function to obtain references to your views in
Activities or Fragments.
For example,
consider the following activity XML layout:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="co.ikust.kotlintest.MainActivity">
<TextView android:id="@+id/helloWorldTextView“ android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</RelativeLayout>
Import kotlinx.android.synthetic.main.activity_main.*
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
helloWorldTextView.text = "Hello World!"
} }
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView tv=findViewById(R.id.helloWorldTextView);
tv.setText(“Hello World!”);
}
}

9. 9
#2 Writing POJO Classes with Kotlin
public class User {
private String firstName;
private String lastName;
Sting fullname
Stign address
public String
getFirstName() {
return firstName;
}
public void
setFirstName(String
firstName) {
this.firstName =
firstName;
}
public String
getLastName() {
return lastName;
}
public void
setLastName(String
class User {
var firstName: String? = null
Var aadress:String?
var lastName: String? = null
}
Custom accessors can be written, for example:
class User {
var firstName: String? = null
var lastName: String? = null
val fullName: String? get() firstName + " " + lastName }
This saves lots of lines of code

10. 10
#3 Class Inheritance and Constructors
Kotlin classes have a primary constructor and one or more secondary constructors.
An example of defining a primary constructor:
class User constructor (firstName: String, lastName: String){ }
class User(val firstName: String, val lastName: String) {
constructor(firstName: String) : this(firstName, "")
{ //... }
}
Secondary constructor
Inheritance
In Kotlin, all classes extend from Any, which is similar to Object in Java. By default, classes are
closed, like final classes in Java. So, in order to extend a class, it has to be declared as open or
abstract:
open class User(val firstName, val lastName) class Administrator(val firstName, val lastName)
: User(firstName, lastName)

11. 11
#4 Lambda Expressions
fun add(x: Int, y: Int = 1) : Int
{
return x + y;
}
int add(int x)
{
return add(x, 1);
}
int add(int x, int y)
{
return x + y;
} Using Lambda Expressions
view.setOnClickListener(
{ view -> toast("Click")
})
view.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v) {
Toast.makeText(v.getContext(), "Clicked on view",
Toast.LENGTH_SHORT).show();
}
};

12. 12
#5 Null Safety
No more Null Pointer Exceptions
Kotlin’s type system is aimed to eliminate this forever.
//Null Safety
var a: String = "abc"
a = null // compilation error
var b: String? = "abc"
b = null // ok
// what about this ?
val l = a.length // Promise no NPE crash
val l = b.length // error: b can be null

13. 13
#6 Extensions and Smart Cast
public static boolean isTuesday(Date
date) {
return date.getDay() == 2;
}
boolean tuesdayBool =
DateUtils.isTuesday(date);
fun Date.isTuesday(): Boolean {
return getDay() ==2
}
val dateToCheck = Date()
println(date.isTuesday())
Extensions
Smart Cast
if (obj instanceOf MyType) {
((MyType)obj).getXValue();
} else {
// Oh no do more
}
if (obj is MyType) {
obj.getXValue()
} else {
// Oh no do more
}

14. 14
… and More
• Visibility Modifiers
• Companion Objects
• Nested, Sealed Classes
• Generics
• Coroutines
• Operator overloading
• Exceptions
• Annotations
• Reflection
• and more
… and Even More
• Infix extension methods
• Interfaces
• Interface Delegation
• Property Delegation
• Destructuring
• Safe Singletons
• Init blocks
• Enums
• Multiline Strings
• Tail recursion
source http://kotlinlang.org/

15. 15
NUMBER OF ANDROID APPS IN KOTLIN
2018 2019
Stats from Jetbrains.com
(Projection)

16. 16
For more information…
• https://developer.android.com/kotlin/
• https://www.jetbrains.com/opensource/kotlin/
• https://discuss.kotlinlang.org/
• https://kotlinlang.org/docs/reference/android-overview.html
Source https://developer.android.com/kotlin/

17. FURTHER SUPPORT AND INTEGRATIONS
FOR KOTLIN
• start.spring.io
• Kotlin Compiler Plugin
• Kotlin Support in Spring 5.0
• Kotlin Gradle DSL
• @TestInstance(
Lifecycle.PER_CLASS)
• Kotlin Android Extensions

18. 18
THANK YOU
Phani Gullapalli.