Java Reference
In-Depth Information
Sets
A set is a collection that contains no duplicate elements. There are two kinds of sets, the immutable
and the mutable. Listing C-7 illustrates how to create an immutable set.
Listing C-7. Creating an Immutable Set
val set = Set(1, 2, 3, 2, 3)
println ("head -- "+set.head)
println("tail -- "+set.tail)
println("size -- "+set.size)
println("sum -- "+set.sum)
head -- 1
tail -- Set(2, 3)
size -- 3
sum -- 6
By default, Scala uses the immutable set. If you want to use the mutable set, you will have to import
scala.collection.mutable.Set
. Listing C-8 illustrates how to create and use a mutable set.
Listing C-8. Creating a Mutable Set
import collection.mutable
val set = mutable.HashSet(1, 2, 3, 2, 3)
assert (set.size == 3)
Maps
A Scala map is a collection of key-value pairs. By default, Scala uses the immutable map. If you
want to use the mutable map, you'll have to import the
scala.collection.mutable.Map
class
explicitly. Listing C-9 illustrates how to create and use an immutable map.
Listing C-9. Creating an Immutable Map
val map = Map("1" -> 1, "2" -> 2, "3" -> 3, "2" -> 2, "3" -> 3)
println ("head -- "+map.head)
println("tail -- "+map.tail)
println("size -- "+map.size)
head -- (1,1)
tail -- Map(2 -> 2, 3 -> 3)
size -- 3
