Kotlin Tutorial (Programing Language)
By: Luis A. Sierra
Introduction
Kotlin is easy to learn, especially if you already know Java (it is 100% compatible with Java).
Kotlin is used to develop Android apps, server side apps, and much more
What is Kotlin
Kotlin is widely used for Android due to its interoperability with Java, its conciseness, and its excellent security features.
History
Kotlin was developed by JetBrains in 2010. They initially released it under the name Project Kotlin in July 2011. They needed a language that was concise, elegant, expressive, and also interoperable with Java, as most of their products were developed in Java, including the Intellij Idea. They were looking for an alternate language to reduce the amount of boilerplate code required and to introduce new constructs, such as higher-order functions, to make language more expressive and concise. One of the goals of the Kotlin language was to be able to compile code as quickly as Java.
JetBrains open-sourced the project under the Apache 2 license in February 2012. Kotlin v1.0 was released on February 15, 2016.
Kotlin Get Started
Hello, World! It is the first basic program in any programming language. Let's write the first program in the Kotlin programming language.
println("Hello, world!!!")
}
Copy the code below and run it at: https://play.kotlinlang.org
Kotlin Comments
fun main() {
// This is a comment
println("Welcome to http://interesting-homemade-projects")
}
Copy the code below and run it at: https://play.kotlinlang.org
Multi-line comments start with /* and ends with */.
fun main() {
/* The code below will print the url of my web site
to the screen */
println("Welcome to http://interesting-homemade-projects")
}
Copy the code below and run it at: https://play.kotlinlang.org
Kotlin Variables
To create a variable, use var or val, and assign a value to it with the equal sign (=):
fun main() {
var Thousand = 1000;
println(Thousand)
val Pi = 3.14;
println(Pi)
var AuthorName = "Luis A. Sierra";
println(AuthorName)
}
Copy the code below and run it at: https://play.kotlinlang.org
Note:
The difference between var and val is that variables declared with the var keyword can be changed/modified, while val variables cannot.
Case SensitivityCase sensitivity defines whether uppercase and lowercase letters are treated as distinct or equivalent.
"kotlin : is case sensitive"
Kotlin Data Type
fun main() {
val id = 10 // Int
val percentage = 18.55 // Double
val gender = 'M' // Char
val isVerified = true // Boolean
val name = "Luis A. Sierra" // String
println("Id: " + id)
println("Name: " +name)
println("Percentage: " + percentage)
println("Gender: " + gender)
println("Verfied: " + isVerified)
}
fun main() {
val id : Int = 10 // Int val percentage : Double = 18.55 // Double val gender : Char = 'M' // Char val isVerified : Boolean = true // Boolean val name : String = "Luis A. Sierra" // String
println("Id: " + id) println("Name: " +name) println("Percentage: " + percentage) println("Gender: " + gender) println("Verfied: " + isVerified) }
Copy the code below and run it at: https://play.kotlinlang.org 
Type ConversionsIs the process of converting one data type to another. The type conversion is only performed to those data types where conversion is possible.
The following table lists some of the built-in methods from the Convert class that you can use.
fun main() {
val num : Int = 10
val dec : Double = 5.25
val boolean : Boolean = true
println(num.toString()) //Convert to String
println(num.toDouble()) //Convert to Double
println(dec.toInt()) //Convert to Int
println(boolean.toString()) //Convert to String
}
Copy the code below and run it at: https://play.kotlinlang.org
MORE EXAMPLES:
* Convert to String
* Convert to Integer
* Convert to Double
* Convert to Boolean
* Convert to Date
* Convert to Time
* Convert to DateTime
* Format DateTime
* DayName of DateTime
* Convert to ASCII
* String Replace
* String Length
* String Copy
Kotlin Array
println(names[0])
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val names = arrayOf("Luis A. Sierra", "Maria Ramirez", "Jose Valdez", "Roberto Baez")
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println(names.size)
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OperatorsIn Kotlin different types of operators are available; those are:
- Arithmetic Operators
- Relational Operators
- Logical Operators
- Bitwise Operators
- Assignment Operators
Arithmetic Operators
Arithmetic operators are used to perform common mathematical operations.
Assignment Operators
Assignment operators are used to assign values to variables.
Comparison operators are used to compare two values (or variables). This is important in programming, because it helps us to find answers and make decisions.
Logical operators are used to determine the logic between variables or values:
if/else Statement
WHEN Statement
While Statement
A while loop is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition.
For Statement
Traditional for:
Function
Note: functions return and not return a value.
Class
Constructor
PropertiesProperties are special attributes or characteristics associated with an object. They encapsulate data and provide access control through getter and setter methods, allowing you to interact with the object's state without directly accessing its variables.
InheritanceInheritance is one of the core features of object-oriented programming. It's a programming procedure that allows you to reuse code by referencing the behaviors and data of an object. In other words, a class that inherits from another class shares all the attributes and methods of the referenced class.
Exception handling
Tutorial's Files:
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