Handling InputStream in Scala

Question

I have a method that takes inputStream as a parameter. An InputStream, which contains the following

• input:

• A line containing a single number: N

• Followed by N lines containing two numbers Ti and Li separated by space.

• There may be a trailing newline.

The question is: How do I read and manipulate the stream in scala?

def process(in: InputStream): Long = ???

Answer 1

Following code sample read n from the first line then for each line calculate multiplication of ti * li and total sum.

import java.io.InputStream
import java.io.ByteArrayInputStream
import java.nio.charset.StandardCharsets

import scala.io.Source
import scala.util.matching.Regex

  def process(in: InputStream): Long = {
    val lines = Source.fromInputStream(in).getLines()
    val n = lines.next().toInt
    val pattern: Regex = """\s*(\d+)\s+(\d+)\s*""".r
    lines.map {
      case pattern(ti, li) => ti.toInt * li.toInt
      case _ => 0
    }.sum
  }

  test("process InputStream") {
    val lines =
      raw"""3
           |1 10
           |2 200
           |3 3000
           |""".stripMargin
    println(lines)
    val is: InputStream = new ByteArrayInputStream(lines.getBytes(StandardCharsets.UTF_8))

    assert(process(is) == 9410)
  }