build.sbt

// Add the POI core and OOXML support dependencies into your build.sbt
libraryDependencies ++= Seq(
  "org.apache.poi" % "poi" % "3.15-beta2",
  "org.apache.poi" % "poi-ooxml" % "3.15-beta2",
  "org.apache.poi" % "poi-ooxml-schemas" "3.15-beta2"
)

XSSFMain.scala

// Import the required classes
import org.apache.poi.xssf.usermodel.XSSFWorkbook
import java.io.FileOutputStream

object XSSFMain extends App {

  // Automatically convert Java collections to Scala equivalents
  import scala.collection.JavaConversions._

  // Read the contents of the workbook
  val workbook = new XSSFWorkbook("SampleSS.xlsx")
  for {
    // Iterate and print the sheets
    (sheet, i) <- workbook.zipWithIndex
    _ = println(s"Sheet $i of ${workbook.getNumberOfSheets}: ${sheet.getSheetName}")

    // Iterate and print the rows
    row <- sheet
    _ = println(s"\tRow ${row.getRowNum}")

    // Iterate and print the cells
    cell <- row
  } {
    println(s"\t\t${cell.getColumnIndex}: ${cell.getStringCellValue}")
  }

  // Add a sheet to the workbook
  val sheet = workbook.createSheet("new sheet")
  val row = sheet.createRow(7)
  val cell = row.createCell(42)
  cell.setAsActiveCell()
  cell.setCellValue("The answer to life, the universe, and everything")

  // Save the updated workbook as a new file
  val fos = new FileOutputStream("UpdatedSampleSS.xlsx")
  workbook.write(fos)
  workbook.close()
}