File Handling in Scala

File Handling is a way to store the fetched information in a file. Scala provides packages from which we can create, open, read and write the files. For writing to a file in scala we borrow java.io._ from Java because we don’t have a class to write into a file, in the Scala standard library. We could also import java.io.File and java.io.PrintWriter

Create a New File

• java.io.File defines classes and interfaces for the JVM access files, file system and attributes.
• File(String pathname) converts the parameter string to abstract path name create a new file instance.

Writing to File

• java.io.PrintWriter includes all the printing methods include in PrintStream.

import java.io.File
import java.io.PrintWriter

object demo {
  def main(args : Array[String]){
    // Creating a file
    val file_Object = new File("C:\\Users\\Vinayak\\Desktop/abc.txt" )
    // Passing reference of file to the printwriter
    val print_Writer = new PrintWriter(file_Object)
    // Writing to the file
    print_Writer.write("Hi Welcome, Thanks for Learing File Handling ")
    // Closing printwriter
    print_Writer.close()
  }
}

Reading a File

scala.io.Source includes methods for inerrable representation of the source file.

• Source. fromFile creates a source from the input file.
• file.next return the next element in the iteration and moves the iterator one step ahead.
• file.hasnext checks if there is next element available to iterate.
• getLines– Iterate through file line by line

object test13 {
   def main(args : Array[String]){
     val filename = "C:\\Users\\Vinayak\\Desktop/ddl.txt"   
    for (line <- Source.fromFile(filename).getLines) {
  println(line)
}
}
}


How Do I Append To The List?

In scala to append into a list, use “:+” single value

       var myList = List.empty[String]

       myList :+= "a"

       myList :+= "b"

       myList :+= "c"

       use++ for appending a list

       var myList = List.empty[String]

       myList ++= List("a", "b", "c")

import java.io.File
import java.io.PrintWriter
import scala.io.Source

object Demo {
  def main(args : Array[String]){
    // Creating a file
    val file_Object = new File("C:\\Users\\pundr\\OneDrive\\Desktop/abc.txt" )
    // Passing reference of file to the printwriter
    val print_Writer = new PrintWriter(file_Object)
    // Writing to the file
    print_Writer.write("Hi Welcome, Thanks for Learing File Handling ")
    // Closing printwriter
    print_Writer.close()
    Source.fromFile("C:\\Users\\pundr\\OneDrive\\Desktop/abc.txt" ).foreach { x => print(x) }
  }
}

 What is ofDim in Scala?

ofDim() is a method in Scala that lets us create multidimensional arrays. Since these let us store data in more than one dimension, we can store data like in a matrix. Let’s take an example.

    scala> import Array.ofDim

    import Array.ofDim

    scala> var a=ofDim[Int](3,3)

    a: Array[Array[Int]] = Array(Array(0, 0, 0), Array(0, 0, 0), Array(0, 0, 0))

    scala> var k=1

    k: Int = 1

    scala> for(i<-0 to 2){

        | for(j<-0 to 2){

        | a(i)(j)={i+k}

        | k+=1

        | }

        | k-=1

        | }

    scala> a 

What is a BitSet?

A bitset is a set of non-negative integers depicted as arrays. These arrays are variable in size and packed into 64-bit words. The largest number in a bitset determines its memory footprint. Let’s take an example.

    scala> import scala.collection.immutable._
    import scala.collection.immutable._
    scala> var nums=BitSet(7,2,4,3,1)
    nums: scala.collection.immutable.BitSet = BitSet(1, 2, 3, 4, 7)
    scala> nums+=9  //Adding an element
    scala> nums

res14: scala.collection.immutable.BitSet = BitSet(1, 2, 3, 4, 7, 9) 

What is a vector in Scala?

A vector is a general-purpose data structure that is immutable. We can use it when we want to hold a huge number of elements and want random access to them. This data structure extends the trait IndexedSeq and the abstract class AbstractSeq.

    scala> import scala.collection.immutable._
    import scala.collection.immutable._
    scala> var v1=Vector.empty
    v1: scala.collection.immutable.Vector[Nothing] = Vector()
    scala> var v2=Vector(7,2,4,3,1)
    v2: scala.collection.immutable.Vector[Int] = Vector(7, 2, 4, 3, 1)
    scala> var v3:Vector[Int]=Vector(8,2,6,5,9)
    v3: scala.collection.immutable.Vector[Int] = Vector(8, 2, 6, 5, 9)
    scala> v3=v3 :+7  //Adding a new element
    v3: scala.collection.immutable.Vector[Int] = Vector(8, 2, 6, 5, 9, 7)
    scala> v2++v3  //Merging two vectors

res19: scala.collection.immutable.Vector[Int] = Vector(7, 2, 4, 3, 1, 8, 2, 6, 5, 9, 7)

    scala> v3.reverse  //Reversing a vector

res20: scala.collection.immutable.Vector[Int] = Vector(7, 9, 5, 6, 2, 8)

import scala.io.Source
object demo {
  def main(args : Array[String]){
    val filename = "C:\\Users\\Vinayak\\Desktop/abc.txt"
    for (line <- Source.fromFile(filename).getLines) {
      println(line)
    }
  }
}

// Scala File handling program
import scala.io.Source

// Creating object
object demo
{
  // Main method
  def main(args : Array[String])
  {
    // file name
    val fname = "C:\\Users\\Vinayak\\Desktop/abc.txt"
    // creates iterable representation
    // of the source file
    val fSource = Source.fromFile(fname)
    while (fSource.hasNext)
    {
      println(fSource.next)
    }
    // closing file
    fSource.close()
  }
}

// Scala file handling program to Read each
// line from a single file
import scala.io.Source
// Creating object
object demo
{
  // Main method
  def main(args:Array[String])
  {
    val fname = "C:\\Users\\Vinayak\\Desktop/abc.txt"
    val fSource = Source.fromFile(fname)
    for(line<-fSource.getLines)
    {
      println(line)
    }
    fSource.close()
  }
}