Arrays are mutable, indexed collections of values.Array[T] is Scala's representation for Java'sT[].

val numbers = Array(1, 2, 3, 4)val first = numbers(0) // read the first elementnumbers(3) = 100 // replace the 4th array element with 100val biggerNumbers = numbers.map(_ * 2) // multiply all numbers by two

Arrays make use of two common pieces of Scala syntactic sugar, shown on lines 2 and 3 of the above example code. Line 2 is translated into a call toapply(Int), while line 3 is translated into a call toupdate(Int, T).

Two implicit conversions exist inscala.Predef that are frequently applied to arrays: a conversion toscala.collection.ArrayOps (shown on line 4 of the example above) and a conversion toscala.collection.mutable.ArraySeq (a subtype ofscala.collection.Seq). Both types make available many of the standard operations found in the Scala collections API. The conversion toArrayOps is temporary, as all operations defined onArrayOps return anArray, while the conversion toArraySeq is permanent as all operations return aArraySeq.

The conversion toArrayOps takes priority over the conversion toArraySeq. For instance, consider the following code:

val arr = Array(1, 2, 3)val arrReversed = arr.reverseval seqReversed : collection.Seq[Int] = arr.reverse

ValuearrReversed will be of typeArray[Int], with an implicit conversion toArrayOps occurring to perform thereverse operation. The value ofseqReversed, on the other hand, will be computed by converting toArraySeq first and invoking the variant ofreverse that returns anotherArraySeq.