A Scala Map is a collection of key/value pairs, where the keys must be unique.
Notes:
- There are immutable and mutable versions; immutable is the default.
- There are different types of Maps for different needs (sorted Maps, etc.).
This video demonstrates the the default, immutable Map.
Examples
Scala Map examples using my CRUD approach:
// CREATE
val states = Map(
"AL" -> "Alabama",
"AK" -> "Alaska",
)
// READ
states("AL")
states("foo") // java.util.NoSuchElementException:
// key not found: foo
states.get("AL") // Option[String] = Some(Alabama)
states.getOrElse("AX", "not found") // "not found"
// READ with for-expression (note that `(k, v)` is a tuple)
val ucMap = for
(k, v) <- states
yield
(k, v.toUpperCase)
// UPDATE
val states2 = states + ("CO" -> "Colorado")
val states3 = states2 ++ Map(
"AR" -> "Arkansas",
"AZ" -> "Arizona"
)
// DELETE (by key)
val states4 = states3 - "AL"
val states5 = states4 -- Seq("AZ", "AR")
// map method with Map data type
val states6 = states5.map( (k, v) => (k, v.toUpperCase) )
