Question

我只想从科萨拉的CSV档案中找到第一线,我如何在没有使用Line(0)的情况下这样做?

Answer 1

FWIW, here s what I would do (sticking w/ the standard library):

def firstLine(f: java.io.File): Option[String] = {
  val src = io.Source.fromFile(f)
  try {
    src.getLines.find(_ => true)
  } finally {
    src.close()
  }
}

注:

The function returns Option[String] instead of List[String], since it always returns one or none. That s more idiomatic Scala.
The src is properly closed, even in the very off chance that you could open the file, but reading throws an exception
Using .find(_ => true) to get the first item of the Iterator doesn t make me feel great, but there s no nextOption method, and this is better than converting to an intermediate List you don t use.
IOExceptions opening or reading the file are passed along.

我还建议使用scala-arm图书馆,在你需要时,向您提供更好的预报,以便管理资源和自动结案档案。

import resource._

def firstLine(f: java.io.File): Option[String] = {
  managed(io.Source.fromFile(f)) acquireAndGet { src =>
    src.getLines.find(_ => true)
  }
}

Answer 2

如果你在使用档案后不注意释放档案资源,那么,以下做法非常方便:

Source. fromFile ("myfile.csv”).getLines.next(

Answer 3

如果你想要关闭档案,那么你想要获得一个空洞的收集,而不是在档案实际上空洞的情况下留下一个错误,那么,你就希望得到一个空洞的收集,而不是一个错误。

val myLine = {
  val src = Source.fromFile("myfile.csv")
  val line = src.getLines.take(1).toList
  src.close
  line
}

如果你把海山限制在标准图书馆,你可以做的最短路。

Answer 4

我认为,所有其他解决办法要么按所有思路阅读,要么只保留第一行,要么不关闭档案。解决这些问题的办法如下:

val firstLine = {
  val inputFile = Source.fromFile(inputPath)
  val line = inputFile.bufferedReader.readLine
  inputFile.close
  line
}

如果我错的话,我只有一周在Schala的经验对我非常正确。

友情链接