PopulationStat.scala

// in the name of ALLAH

case class PopulationStat(
  val country: String,
  val symbol: String,
  val year: Int,
  val amount: Long
)

class WritablePopulationStat extends WritableComparable[WritablePopulationStat] {
  def this(v:PopulationStat) = { value = v }
  var value: PopulationStat = _
  private val text = new Text
  
  def wrtie(out: DataOutput) = {
    
    text set value.symbol
    text write out
    
    WritableUtils writeVInt(out, value.year)
    WritableUtils writeVLong(out, value.amount)
    
    text set value.country
    text write out
    
  }
  ...
}