Array creation and usage in Kotlin - Step-by-Step Execution

Concept Flow - Array creation and usage

Start

↓

Create Array

↓

Access Elements

↓

Modify Elements

↓

Use Array in Code

↓

End

This flow shows how to create an array, access and modify its elements, then use it in your program.

Execution Sample

Kotlin

fun main() {
  val numbers = arrayOf(10, 20, 30)
  println(numbers[1])
  numbers[2] = 40
  println(numbers.joinToString())
}

This code creates an array, prints the second element, changes the third element, then prints all elements.

Execution Table

Step	Action	Array State	Output
1	Create array with elements 10, 20, 30	[10, 20, 30]
2	Access element at index 1	[10, 20, 30]	20
3	Modify element at index 2 to 40	[10, 20, 40]
4	Print all elements joined by comma	[10, 20, 40]	10, 20, 40

💡 Program ends after printing the final array state.

Variable Tracker

Variable	Start	After Step 1	After Step 3	Final
numbers	null	[10, 20, 30]	[10, 20, 40]	[10, 20, 40]

Key Moments - 3 Insights

Why does numbers[1] print 20 and not 10 or 30?

Because array indexing starts at 0, numbers[1] accesses the second element, which is 20 (see execution_table step 2).

What happens when we assign numbers[2] = 40?

The third element (index 2) changes from 30 to 40, updating the array state (see execution_table step 3).

Why do we use joinToString() to print the array?

Printing the array directly prints its contents like '[10, 20, 40]' with brackets; joinToString() creates a readable comma-separated string without brackets (see execution_table step 4).

Visual Quiz - 3 Questions

Look at the execution_table, what is the output at step 2?

A 30

B 10

C 20

D 40

💡 Hint

Check the 'Output' column at step 2 in the execution_table.

At which step does the array change its third element?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look at the 'Action' and 'Array State' columns in execution_table for the step where modification happens.

If we changed numbers[0] = 50 at step 3, what would be the final array?

A [10, 20, 40]

B [50, 20, 40]

C [50, 20, 30]

D [10, 20, 30]

💡 Hint

Refer to variable_tracker and imagine changing the first element at step 3.

Concept Snapshot

Array creation: val arr = arrayOf(1, 2, 3)
Access elements: arr[index], index starts at 0
Modify elements: arr[index] = newValue
Use joinToString() to print array nicely
Arrays hold fixed-size collections of items

Full Transcript

This example shows how to create an array in Kotlin using arrayOf with initial values. We access elements by their index starting at zero, so numbers[1] is the second element. We can change elements by assigning a new value to a specific index. Printing the array directly shows its contents with brackets like [10, 20, 40], so we use joinToString() to print elements clearly without brackets. The variable 'numbers' changes as we modify the array. The program ends after printing the final array.