scala-collections

I know how I can use the Java libraries, and I can write some loops that do the stuff I need for me, but the question is more, why is there nothing in scala.collection.JavaConverters or scala.collection.JavaConverstions to convert a java.util.stream.Stream to a scala.collection.immutable.Stream ? I would like to do something like this: def streamFiles(path: Path): Stream[Path] = { Files.newDirectoryStream(path).asScala } But instead I have to write something like this: def streamFiles(path: Path): Stream[Path] = { val path_it : java.util.Iterator[Path] = Files.newDirectoryStream(path).iterator

I'm going through log file that is too big to fit into memory and collecting 2 type of expressions, what is better functional alternative to my iterative snippet below? def streamData(file: File, errorPat: Regex, loginPat: Regex): List[(String, String)]={ val lines : Iterator[String] = io.Source.fromFile(file).getLines() val logins: mutable.Map[String, String] = new mutable.HashMap[String, String]() val errors: mutable.ListBuffer[(String, String)] = mutable.ListBuffer.empty for (line <- lines){ line match { case errorPat(date,ip)=> errors.append((ip,date)) case loginPat(date,user,ip,id) =

If I write class Things extends scala.collection.immutable.HashSet[Int] new Things + 5 Then the result is res0: scala.collection.immutable.HashSet[Int] = Set(5) What do I need to do for the result to be of type Things ? I suspect the answer might be here , but am struggling to understand what's going on. I can't really tell without a sample of your code but you can take a look at Jesse Eichar's post which provides a walk through the implementation of a custom collection and addresses your question nicely. http://daily-scala.blogspot.com/2010/04/creating-custom-traversable.html 来源： https:/

This could be a very silly question, but I am not able to understand the difference even after scratching my head for a long time. I am going through the page of scala generics: https://docs.scala-lang.org/tour/generic-classes.html Here, it is said that Note: subtyping of generic types is invariant . This means that if we have a stack of characters of type Stack[Char] then it cannot be used as an integer stack of type Stack[Int]. This would be unsound because it would enable us to enter true integers into the character stack. To conclude, Stack[A] is only a subtype of Stack[B] if and only if B

Why is there a lack of consistency between Sets and Lists in Scala Collections API? For example, there is immutable Set, but also a mutable one. If I want to use the latter, I can simply do this: val set = Set[A]() set += new A However, there is no mutable List, per se. If I want to write a similar code snippet using Lists, which data structure to use? LinkedList sounds as a good candidate, because it is mutable, but has no += method defined. ListBuffer seems to satisfy the requirements, but it is not a list. After reading 2.8 Collections docs I come to the conclusion MutableList is probably