ListBuffer

val l = ListBuffer[Int](1)
l += 2 // (1,2)

val l = ListBuffer[Int](1)
l ++ ListBuffer(3, 4) // (1,3,4)

val l = ListBuffer[Int](1)
l ++: ListBuffer(3, 4) // (3,4, 1)

Stack

import scala.collection.mutable.Stack 
val stack = Stack[Int]()
stack.push(1)
stack.pop()
stack.top()