Scala - Collection


Scala defines several collection classes:



  • Iterable (collections you can iterate on)
  • Seq (ordered sequences)
  • Set
  • Map (lookup data structure)


  • List (linked list, provides fast sequential access)
  • Stream (same as List, except that the tail is evaluated only on demand)
  • Vector (array-like type, implemented as tree of blocks, provides fast random access)
  • Range (ordered sequence of integers with equal spacing)
  • String (Java type, implicitly converted to a character sequence, so you can treat every string like a Seq[Char])
  • Map (collection that maps keys to values)
  • Set (collection without duplicate elements)


  • Array (Scala arrays are native JVM arrays at runtime, therefore they are very performant)
  • Scala also has mutable maps and sets; these should only be used if there are performance issues with immutable types

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