Question

object Futures4 extends App {

  // get an array of all files in a directory tree
  def recursiveListFiles(f: File): Array[File] = {
    val these = f.listFiles
    these ++ these.filter(_.isDirectory).flatMap(recursiveListFiles)
  }

  val files = recursiveListFiles(new java.io.File("path"))

  // convert to a list of full file paths
  val fileNames = files.toList map (_.getAbsolutePath)
  println(fileNames)

  val n: Int = fileNames.length

  val futures = for {
    i <- 0 to n-1
  } yield future { line_num(i) }

  // read a file by line
  def line_num(i: Int) : Int = 
  {
    for 
    {
      line <- Source.fromFile(fileNames(i)).getLines    
      //here i am getting multiple errors saying type mismatch

    }yield line.length 
  }

  val sumF = Future.fold(futures)(0)(_ + _)
  val sum = Await.result(sumF, 2 seconds)
  println(sum)
}

我想计算所有文件中的行数。我是Scala编程的新手，所以任何帮助都将不胜感激！我在一步提到多个错误，我已经提到过评论。感谢

Answer 1

line_num(i)返回文件i中的行数。所以你可以写下来：

def line_num(i: Int) : Int = {
    Source.fromFile(fileNames(i)).getLines.size
}

在原始函数中，返回Seq(Int)，它是文件中每行长度的序列，与预期的返回类型不对应。

在scala中使用期货读取文件中的行数时出错

1 个答案: