Thinking in scala (1)----类

ChecksumAccumulator.scala

import scala.collection.mutable.Map

class ChecksumAccumulator {
  private var sum = 0
  def add(b: Byte) { sum += b }
  def checksum(): Int = ~(sum & 0xFF) + 1
}

object ChecksumAccumulator {
  private val cache = Map[String, Int]()
  def calculate(s: String): Int =
  if (cache.contains(s))
    cache(s)
  else {
    val acc = new ChecksumAccumulator
    for (c <- s)
      acc.add(c.toByte)
    val cs = acc.checksum()
    cache += (s -> cs)
    cs
  }
}

Summer.scala

import ChecksumAccumulator.calculate

object Summer {
  def main(args: Array[String]) {
    for (arg <- args)
      println(arg +": "+ calculate(arg))
  }
}

$ scalac Summer.scala ChecksumAccumulator.scala

$ scala Summer of love

Program output:

of: -213

love: -182