Array size

Learn array info with size and indices.

Array size

The size of an array is given by the size property. indices gives the range of valid indices (0..size-1), lastIndex gives the last index.

val nums = intArrayOf(3, 7, 2, 5)
println(nums.size)        // 4
println(nums.lastIndex)   // 3
println(nums.indices)     // 0..3

In a 4-element array, size is 4, lastIndex is 3 (since indices start at 0), indices is 0..3. These are useful in loops and bounds checks.

size is a property; no parentheses needed.

Exercise Print size and last index

Write a fun main(). Create an array with val nums = intArrayOf(3, 7, 2, 5). Print the size with println(nums.size) and the last index with println(nums.lastIndex).

Show example solution

fun main() {
    val nums = intArrayOf(3, 7, 2, 5)
    println(nums.size)
    println(nums.lastIndex)
}

Iterating with indices

indices returns a range; it is useful for iterating by index in a for loop.

val nums = intArrayOf(3, 7, 2, 5)
for (i in nums.indices) {
    println(nums[i])
}

This takes each index in turn and accesses the element with nums[i]. indices is the range from 0 to lastIndex.

Index-based iteration is useful when you also need the element's position.

Test yourself

Complete the size call
```
println(nums.____)
```
Show answer
```
println(nums.size)
```
Match the size properties

size

Element count
lastIndex

Last index
indices

Index range
0..3

4-element array range
In a 4-element array, what is lastIndex?
- 4
- 3
- 0
- 1
Show answer

3 — Since indices start at 0, the last index is 3.

Next lesson: Array loop

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