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Summary - Loops

Combine for, while and range to write a multiplication table.

Summary - Loops

In this summary you'll combine for, while and ranges to build a multiplication table. In previous lessons you learned:

  • counted loops with for (i in 1..5)
  • conditional loops with while
  • at-least-once loops with do-while
  • ranges with 1..5, until, downTo

We'll do two mini tasks: print a row of the multiplication table (for + range) and count down (while).

Practice 3 times table

Write a fun main(). Use a for (i in 1..5) loop to print println("3 x $i = ${3 * i}"). Output: 3 x 1 = 3, 3 x 2 = 6, ..., 3 x 5 = 15.

Starter code

Main.kt
fun main() {
    // 3 times table
}

Sample solution

Main.kt
fun main() {
    for (i in 1..5) {
        println("3 x $i = ${3 * i}")
    }
}

Expected output

3 x 1 = 3
3 x 2 = 6
3 x 3 = 9
3 x 4 = 12
3 x 5 = 15

Practice Count down with while

Write a fun main(). Assign 5 to var n. Use a while (n > 0) loop to print println(n) and decrease with n = n - 1 each step. The output should be 5, 4, 3, 2, 1.

Starter code

Main.kt
fun main() {
    // Count down
}

Sample solution

Main.kt
fun main() {
    var n = 5
    while (n > 0) {
        println(n)
        n = n - 1
    }
}

Expected output

5
4
3
2
1

Questions and answers

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

1 Which range counts 1 to 5 (5 inclusive)?

  • 1 until 5
  • 1..5 Correct answer
  • 5 downTo 1
  • 1..4

Explanation: 1..5 includes both ends: 1, 2, 3, 4, 5.

2 Complete the range

Question 
for (i in 1____5) { println("3 x $i = ${3 * i}") }
Answer 
for (i in 1..5) { println("3 x $i = ${3 * i}") }

Explanation: The 1..5 range counts 1 to 5 (5 inclusive).

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