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Array access

Learn to access array elements by index.

Array access

Array elements are accessed by index: array[0] gives the first element. Indices start at 0.

val fruits = arrayOf("apple", "pear", "cherry")
println(fruits[0])  // apple
println(fruits[2])  // cherry

fruits[0] is the first element ("apple"), fruits[2] the third ("cherry"). Since indices start at 0, the last index of an N-element array is N-1.

Going beyond the bounds throws IndexOutOfBoundsException.

Index bounds and mutation

Array elements can be both read and written with arr[index] (if declared with var).

val nums = intArrayOf(3, 7, 2)
println(nums[1])  // 7
nums[1] = 9
println(nums[1])  // 9

Here nums[1] first gave 7; then nums[1] = 9 changed it to 9. Even with val nums, elements can be changed; only the array itself cannot be reassigned.

Index starts at 0 and goes up to size - 1.

Practice Print the first and last element

Write a fun main(). Create an array with val fruits = arrayOf("apple", "pear", "cherry"). Print the first element with println(fruits[0]) and the last with println(fruits[2]).

Starter code

Main.kt
fun main() {
    // Print the first and last element
}

Sample solution

Main.kt
fun main() {
    val fruits = arrayOf("apple", "pear", "cherry")
    println(fruits[0])
    println(fruits[2])
}

Expected output

apple
cherry

Questions and answers

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

1 Match the indices

Term Meaning
arr[0] First element
arr[1] Second element
arr[N-1] Last element
arr[N] Error (out of bounds)

2 val arr = arrayOf("a", "b", "c") — what does arr[0] return?

  • "a" Correct answer
  • Error
  • "b"
  • "c"

Explanation: arr[0] gives "a", the first element.

3 Complete the first element access

Question 
println(fruits[____])
Answer 
println(fruits[0])

Explanation: fruits[0] gives the first element.

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