Te addString method utilized to append the elements of the Scala Iterator to a String Builder.This method is same as addString() method but here a start, a separator and an end is also included.
Method Definition: def addString(b: mutable.StringBuilder, start: String, sep: String, end: String): mutable.StringBuilder
Where, sep is the separator stated.
Return Type: It returns the elements of the Iterator in the String Builder and a start, a separator and an end is also included here.
So, here the identical element is not removed like in maps.