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List access

Learn list access with get, indexOf and subList.

List access: get, indexOf, subList

There are several ways to reach a list element. get(i) (or [i]) returns the element at index i. indexOf(x) gives the first index where x appears, or -1 if not found. subList(from, to) returns the range [from, to) as a new list.

val fruits = listOf("apple", "banana", "cherry", "grape")
fruits.get(0)              // "apple"
fruits.indexOf("banana")  // 1
fruits.subList(1, 3)       // [banana, cherry]

Indexes start at 0 and end at size - 1. The end of the range (to) is exclusive; that is why subList(1, 3) takes indexes 1 and 2.

The range of subList: [from, to)

subList(from, to) includes index from and excludes index to. So subList(1, 3) gives indexes 1 and 2; index 3 is not included.

val f = listOf("a", "b", "c", "d", "e")
val middle = f.subList(1, 4)  // [b, c, d]

This half-open range matches Kotlin's 1..4 (closed) and 1 until 4 (open) ranges. It makes index math easier.

Practice Print the first fruit, the index and the slice

Create a listOf("apple", "banana", "cherry", "grape"). Use get(0) to assign the first fruit to first, indexOf("banana") for the index i, and subList(1, 3) for the slice. Print each on its own line with println.

Starter code

Main.kt
fun main() {
    val fruits = listOf("apple", "banana", "cherry", "grape")
    // Get the first fruit, find the index of "banana", print the slice 1..3
}

Sample solution

Main.kt
fun main() {
    val fruits = listOf("apple", "banana", "cherry", "grape")
    val first = fruits.get(0)
    val i = fruits.indexOf("banana")
    println(first)
    println(i)
    println(fruits.subList(1, 3))
}

Expected output

apple
1
[banana, cherry]

Questions and answers

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

1 Match access expression to result

Term Meaning
get(0) First element
indexOf(x) Position of x (-1 if missing)
subList(1, 3) Indexes 1 and 2
size - 1 Last index

2 What does list.indexOf("missing") return?

  • 0
  • Throws an exception
  • null
  • -1 Correct answer

Explanation: indexOf returns -1 when not found; no null, no exception.

3 Fill in the blank: get the first element

Question 
val first = fruits.____(0)
Answer 
val first = fruits.get(0)

Explanation: fruits.get(0) returns the first fruit.

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