Appending an element to the end of a list in Scala

Question

I can t add an element of type T into a list List T   I tried with myList     myElement but it seems it creates a strange object and accessing to myList last always returns the first element that was put inside the list  How can I solve this problem

User · Answer

This is similar to one of the answers but in different way   scala gt  val x   List 1 2 3  x  List Int    List 1  2  3   scala gt  val y   x     4    Nil y  List Int    List 1  2  3  4

User · Answer

That s because you shouldn t do it  at least with an immutable list   If you really really need to append an element to the end of a data structure and this data structure really really needs to be a list and this list really really has to be immutable then do eiher this    4    List 1 2 3  reverse  reverse   or that   List 1 2 3      List 4

User · Answer

List 1 2 3     4  Results in List Int    List 1  2  3  4    Note that this operation has a complexity of O n   If you need this operation frequently  or for long lists  consider using another data type  e g  a ListBuffer

User · Answer

Lists in Scala are not designed to be modified  In fact  you can t add elements to a Scala List  it s an immutable data structure  like a Java String   What you actually do when you  add an element to a list  in Scala is to create a new List from an existing List   Source   Instead of using lists for such use cases  I suggest to either use an ArrayBuffer or a ListBuffer  Those datastructures are designed to have new elements added   Finally  after all your operations are done  the buffer then can be converted into a list  See the following REPL example   scala gt  import scala collection mutable ListBuffer import scala collection mutable ListBuffer  scala gt  var fruits   new ListBuffer String    fruits  scala collection mutable ListBuffer String    ListBuffer    scala gt  fruits     Apple  res0  scala collection mutable ListBuffer String    ListBuffer Apple   scala gt  fruits     Banana  res1  scala collection mutable ListBuffer String    ListBuffer Apple  Banana   scala gt  fruits     Orange  res2  scala collection mutable ListBuffer String    ListBuffer Apple  Banana  Orange   scala gt  val fruitsList   fruits toList fruitsList  List String    List Apple  Banana  Orange

User · Answer

We can append or prepend two lists or list amp array Append  var l   List 1 2 3      l   l    4  Result   1 2 3 4   var ar   Array 4  5  6      for x  lt - ar        l   l    x       l foreach println   Result 1 2 3 4 5 6  Prepending  var l   List Int         for x  lt - ar          l  x    l     prepending          l foreach println      Result 6 5 4 1 2 3

[arrays] Appending an element to the end of a list in Scala

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