Insert character in Scala String

Try this

val (fst, snd) = s.splitAt(2)
fst + 'c' + snd

We can use the patch method on Strings in order to insert a String at a specific index:

"abde".patch(2, "c", 0)
// "abcde"

This:

• drops 0 (third parameter) elements at index 2

• inserts "c" at index 2

which in other words means patching 0 elements at index 2 with the string "c".