Scala Infinite Iterator OutOfMemory

object FileProcessor {
  def main(args: Array[String]) {
    val inSource = Source.fromFile("in.txt")
    val outSource = new PrintWriter("out.txt")

    try {
      // this "basic" lazy iterator works fine
      // val iterator = inSource.getLines

      // ...but this one,which incorporates my process method,// throws OutOfMemoryExceptions
      val iterator = process(inSource.getLines.toSeq).iterator

      while(iterator.hasNext) outSource.println(iterator.next)

    } finally {
      inSource.close()
      outSource.close()
    }
  }

  // processing in this case just means upper-cases every line
  private def process(contents: Seq[String]) = contents.map(_.toUpperCase)
}

所以我在大文件上得到一个OutOfMemoryException.我知道如果你保持对流的头部的引用,你可以与Scala的懒惰流相遇.所以在这种情况下,我小心翼翼地将process()的结果转换为迭代器并抛弃最初返回的Seq.

有谁知道为什么这仍会导致O(n)内存消耗？谢谢！

更新

为了回应fge和huynhjl,似乎Seq可能是罪魁祸首,但我不知道为什么.作为一个例子,以下代码工作正常(我在整个地方使用Seq).此代码不会产生OutOfMemoryException：

object FileReader {
  def main(args: Array[String]) {

  val inSource = Source.fromFile("in.txt")
  val outSource = new PrintWriter("out.txt")
  try {
    writeToFile(outSource,process(inSource.getLines.toSeq))
  } finally {
    inSource.close()
    outSource.close()
  }
}

@scala.annotation.tailrec
private def writeToFile(outSource: PrintWriter,contents: Seq[String]) {
  if (! contents.isEmpty) {
    outSource.println(contents.head)
    writeToFile(outSource,contents.tail)
  }
}

private def process(contents: Seq[String]) = contents.map(_.toUpperCase)