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Summary - Data types

Combine Int, Double, String and Boolean to write a calculation card.

Summary - Data types

So far you've learned integer types, floating-point types, Boolean, Char, String, Any and Unit. Each type has a purpose: Int and Long for integers, Double for floating-point, Boolean for conditions, Char for one character, String for text.

Any is the supertype of all; Unit marks functions that return no value.

Practice Put it together

At the top level, declare val name: String = "Kotlin". Inside fun main(), print the length with println(name.length).

Sample solution

Main.kt
val name: String = "Kotlin"

fun main() {
    println(name.length)
}

Expected output

6

Next step

Congratulations! You've completed the data types group. In the next group you'll build a calculator project: step by step you'll add functions and complete a working app from start to finish. You'll experience addition, subtraction, multiplication, division and error handling in a real project.

This project will bring together all the fundamentals you've learned.

Questions and answers

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

1 Which is the default type for floating-point?

  • Float
  • Double Correct answer
  • Int
  • Long

Explanation: Double is the default floating-point type.

2 Match the concepts

Term Meaning
Int Integer
Double Floating-point
Boolean true/false
String Text

3 Summary - Data types: fill in the missing part

Question 
val active: ____ = true
Answer 
val active: Boolean = true

Explanation: A true/false value is of type Boolean.

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