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What is Kotlin?

Learn that Kotlin is a modern JVM-based language.

What is Kotlin?

Kotlin is a modern, statically-typed programming language announced by JetBrains in 2011 and supported today by Google, Android and the Spring ecosystem. Kotlin 2.x is the current long-term release.

Kotlin is a compiled language; source code is turned into JVM bytecode and runs on any JVM (Java Virtual Machine). The same code runs on Windows, Linux and macOS.

It is widely used for Android apps, server services and multiplatform projects.

What can you build with Kotlin?

Kotlin has a wide range of use cases:

  • Android: a large share of mobile apps are written in Kotlin
  • Server side: large systems with Spring and Ktor
  • Multiplatform: shared code with Kotlin Multiplatform
  • Data science: analysis with Kotlin Notebook

This versatility puts Kotlin at the center of modern ecosystems.

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What runs a Kotlin program?

  • Only a compiler
  • A web browser
  • The JVM (Java Virtual Machine) Correct answer
  • The OS kernel

Explanation: Kotlin bytecode runs on the JVM.

2 Match the concepts

Term Meaning
Kotlin Programming language
JVM Runtime
JetBrains Developer company
Android Mobile platform

3 Which can NOT be done with Kotlin?

  • Build an Android app
  • Write a server service
  • Build a multiplatform library
  • Write an OS kernel Correct answer

Explanation: Kernels are typically written in C; Kotlin is not suited for that.

4 Kotlin is an ___ language

Question 
Kotlin is an ____ language.
Answer 
Kotlin is an object-oriented language.

Explanation: Kotlin is an object-oriented language.

All lessons in Beginner

1 Kotlin basics

  1. What is Kotlin?
  2. Your first program
  3. The main function
  4. Comments
  5. String templates
  6. Summary - Kotlin basics

2 Variables

  1. val and var
  2. Type inference
  3. const
  4. lateinit
  5. by lazy
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. Boolean and Char
  4. String
  5. Any and Unit
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Elvis operator
  6. Summary - Operators

6 Strings

  1. Creating strings
  2. String templates
  3. String methods
  4. substring
  5. split and replace
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. if expression
  4. when
  5. when expression
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. Range
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Arrays

  1. Creating arrays
  2. Array access
  3. Array size
  4. Array loop
  5. Array methods
  6. Summary - Arrays

11 Lists

  1. Creating lists
  2. List operations
  3. List access
  4. List iteration
  5. List methods
  6. Summary - Lists

12 Maps and Sets

  1. Creating sets
  2. Set operations
  3. Creating maps
  4. Map operations
  5. Map iteration
  6. Summary - Maps and Sets

13 Functions

  1. Defining functions
  2. Return values
  3. Expression body
  4. Default parameters
  5. Named arguments
  6. Summary - Functions

14 Null safety

  1. Nullable types
  2. ?, !! and ?:
  3. let
  4. Null check
  5. lateinit
  6. Summary - Null safety

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Advanced string operations

  1. Regex
  2. matches and find
  3. replace
  4. StringBuilder
  5. trim and pad
  6. Summary - Advanced strings

17 Enums

  1. enum class
  2. Enum values
  3. Enum properties
  4. when with enum
  5. Enum and range
  6. Summary - Enums

18 Exceptions

  1. try/catch
  2. throw
  3. finally
  4. try expression
  5. Custom exceptions
  6. Summary - Exceptions

19 Class basics

  1. class
  2. Constructor
  3. Properties
  4. Methods
  5. this
  6. Summary - Class basics

20 Beginner final

  1. Project design
  2. Classes
  3. Collections
  4. Error handling
  5. Putting it together