Nested for loop in Scala not iterating through out the file?

Question

I have first file with data as

A,B,C
B,E,F
C,N,P

And second file with data as below

A,B,C,YES
B,C,D,NO
C,D,E,TRUE
D,E,F,FALSE
E,F,G,NO

I need every record in the first file to iterate with all records in the second file. But it's happening only for the first record.

Below is the code:

import scala.io.Source.fromFile

object TestComparision  {

    def main(args: Array[String]): Unit = {
      val lines = fromFile("C:\\Users\\nreddy26\\Desktop\\Spark\\PRI.txt").getLines
      val lines2 = fromFile("C:\\Users\\nreddy26\\Desktop\\Spark\\LKP.txt").getLines
      var l = 0
      var cnt = 0
      for (line <- lines) {

        for (line2 <- lines2) {

          val cols = line.split(",").map(_.trim)
          println(s"${cols(0)}|${cols(1)}|${cols(2)}")

          val cols2 = line2.split(",").map(_.trim)
          println(s"${cols2(0)}|${cols2(1)}|${cols2(2)}|${cols2(3)}")


        }
      }
    }
  }

Were able to get the output like this below: A,B,C A,B,C,YES A,B,C B,C,D,NO A,B,C C,D,E,TRUE A,B,C D,E,F,FALSE A,B,C E,F,G,NO B,E,F A,B,C,YES B,E,F B,C,D,NO B,E,F C,D,E,TRUE B,E,F D,E,F,FALSE B,E,F E,F,G,NO C,N,P A,B,C,YES C,N,P B,C,D,NO C,N,P C,D,E,TRUE C,N,P D,E,F,FALSE C,N,P E,F,G,NO — Ramakrishna Reddy
– Ramakrishna Reddy, Commented May 13, 2021 at 13:16
every row in first set should iterate with second set of data but for me its happening only for first record. — Ramakrishna Reddy
– Ramakrishna Reddy, Commented May 13, 2021 at 13:22
Iterators are only consumed once, so you either need to re-open the file every time, or cache their contents in memory by turning them into a List or a Vector. — Luis Miguel Mejía Suárez
– Luis Miguel Mejía Suárez, Commented May 13, 2021 at 13:57

Saurav Sahu · Accepted Answer · 2021-05-13 14:15:12Z

1

As rightly suggested by @Luis, get the lines in List form by using toList:

val lines = fromFile("C:\\Users\\nreddy26\\Desktop\\Spark\\PRI.txt").getLines.toList
val lines2 = fromFile("C:\\Users\\nreddy26\\Desktop\\Spark\\LKP.txt").getLines.toList

answered May 13, 2021 at 14:15

Saurav Sahu

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