# Exploring Immutable Arrays in Scala: A Deep Dive into Vectors

Scala Array is not located in the **scala.collection.mutable** package, however, they are in fact mutable

```scala
val arr = Array(1,2,3)
arr(1) = 3
println(arr.mkString(",")) // 1,3,3
```

Immutable alternative to Scala Array is Scala Vector

```scala
val arr = Vector(1,2,3)
println(arr.updated(1,3).mkString(",")) // 1,3,3
println(arr.mkString(",")) // 1,2,3 because original array remains unchanged
```

Vector provides O(1) asymptotic time complexity prepend, append, random read, random write operations

### Most important methods of Vector class:

| Method | Description |
| --- | --- |
| vector.update(index, V) | random write, returns a new vector with an updated value V at the specified index |
| vector(index) | random read, returns a value of the index element |
| vector.prepended(V) | returns a new vector with prepended value V |
| vector.appended(v) | returns a new vector with appended value V |