Lists in Scala are immutable. This means that you cannot make changes to it. You also cannot delete elements from it.

val lst1 = List(1,2,3)
println(lst1)

Adding to the List

You have to assign a new List to a Variable in order to add Elements to it.

Prepend

val lst1 = List(1,2,3)
val lst2 = 0 +: lst1
println(lst1)
println(lst2)

• Use the +: to add

If you want to add

You can also use the :: to Concatenate multiple Expressions together.

val lst2 = List(2,3,4);
val lst3 = List(5,6,7);
val lst4 = List(0,1);
val lst1 = lst4 :: lst2 :: lst3;
println(lst1);

Or, you can just add an individual Element.

val list = List(2, 3, 4)
val result = 1 :: list

// Output: List(1, 2, 3, 4)
println(reslut)

Append

val lst1 = List(1,2,3)
val lst2 = lst1 :+ 4
val lst3 = 0 +: lst2
println(lst1)
println(lst2)
println(lst3)

You can also use the ++ Operator to combine (Or Concatenate) multiple Lists into one.

val lst1 = List(1,2,3)
val lst2 = List(4,5,6)
val lst3 = List(7,8,9)
val lst4 = lst1 ++ lst2 ++ lst3
println(lst4)

In the above example, notice where the + symbol is positioned in the code. That is hint on remembering the structure when it comes to Prepending versus Appending Elements.