Why is Scala Map auto-imported but HashMap isn't? -

Why is Scala Map auto-imported but HashMap isn't? -

if utilize map no need import immutable map

scala> val map=map[string,int]() map: scala.collection.immutable.map[string,int] = map()

but if utilize hashmap, without doing import, gives error.

scala> val a=hashmap[int,int]() <console>:7: error: not found: value hashmap val a=hashmap[int,int]() ^

but doing import scala.collection.immutable.hashmap, works.

i see set , hashset..

i notice 1 thing map , set trait , hashset,hashmap classes.

so why ???

edit

class stack , queue exist in scala.collection package. why need import these classes. ???

program interface, not implementation. scala designers encouraged providing shortcuts interfaces in predef.

scala scala-collections