Kotlin Programming Language Tutorial Notes

Introduction to Kotlin

• Kotlin: A statically typed programming language developed by JetBrains
• Popular since its inception in 2011
• Primary language for Android development
• Tutorial Goals:
  • Transition from basic topics to advanced concepts like modeling data and higher order functions
  • Understand application building across mobile, web, and native code

Setting Up Kotlin Environment

1. Install JetBrains IDE (IntelliJ IDEA)

   • Available for Windows, macOS, and Linux
   • Choose between Ultimate Edition (paid, full features) and Community Edition (free, JV, and Android support)
   • Download and install the IDE

2. Create Your First Kotlin Project

   • Open IntelliJ IDEA and create a new project
   • Select Kotlin, and then choose Kotlin Module for JVM Target
   • Name the project, e.g., hello_kotlin
   • Add a Kotlin file, main.kt, for your code

3. Hello World Example

   • Define the main function:

     fun main() {
         println("Hello Kotlin")
     }
     

   • Run your code and observe output.
   • Optional: Use IntelliJ live templates to auto-generate the main function structure.

Kotlin Basics: Variables

• Variable Types in Kotlin:
  • Mutable Variables: var (reassignable)
  • Immutable Variables: val (assigned once)
• Declaring Variables:

  val name: String = "Nate"
  var age: Int = 25
  

• Type System:
  • Non-nullable by default, use ? for nullable types.

Control Flow

• If Statements:

  if (condition) {
      // do something
  } else {
      // do something else
  }
  

• When Statements (similar to switch):

  when (variable) {
      condition -> action
      else -> default
  }
  

Functions in Kotlin

• Define functions with fun keyword:

  fun greet(name: String): String {
      return "Hello, $name" 
  }
  

• Default and Named Parameters:
  • Provide default values in function definitions, e.g., fun greet(name: String = "Guest").
  • Use named arguments to specify function parameters in any order.

Classes and Objects

• Defining a Class:

  class Person(val name: String, var age: Int) {
      fun printInfo() {
          println("Name: "+name+", Age: "+age)
      }
  }
  

• Creating Objects:

  val person = Person("Nate", 25)
  person.printInfo()
  

• Inheritance:
  • Use open to allow classes to be inherited.
• Data Classes:
  • Used for data models, auto-generates necessary methods like equals, hashCode, and toString.

Collections and Iteration

• Working with Collections:
  • Lists, Arrays, and Maps
  • Use functional operations like map, filter

  val numbers = listOf(1, 2, 3, 4, 5)
  val even = numbers.filter { it % 2 == 0 }
  

• Higher Order Functions:
  • Functions that take other functions as parameters or return functions.

  fun <T> List<T>.customFilter(predicate: (T) -> Boolean): List<T> {
      val result = mutableListOf<T>()
      for (item in this) {
          if (predicate(item)) {
              result.add(item)
          }
      }
      return result
  }
  

Summary

• Key Features of Kotlin:
  • Null Safety
  • Extension Functions
  • Functional Programming Capabilities
  • Supports OOP principles such as Classes, Objects, Inheritance, and Data Classes

Conclusion

• With these concepts, you should feel comfortable writing and understanding Kotlin code for various applications.

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