In Scala, scala.collection.mutable implements Stack data structure. The ++: method is similar to ++ method in Stack which gives a new stack with elements from the left hand operand followed by the elements from the right hand operand. But with the difference that in ++:() right operand determines the type of the resulting collection rather than the left one.
Method Definition – def ++:[B >: A, That](that: collection.Traversable[B])
Returns – A new stack which contains all elements of this stack followed by all elements of traversable.
Stack(11, 12, 13, 14, 15, 1, 2, 3, 4, 5)
Stack(1, 2, 3, for, geeks)