scala 没有检查异常  
throw new Exception("error")
在catch块中进行模式匹配
try {
    file.write(stuff)
} catch{
    case e:java.io.IOException => // handle IO Exception
    case n:NullPointerException => // handle null pointer
}

try{
   Integer.parseInt("xxx")
}catch{
   case _ => 0
}



class AIsTooBig extends Exception {}
class BIsTooBig extends Exception {}

object ExceptionDemo {
  def main(args: Array[String]) {
    println(divideTest(6, 3))
    println(divideTest(1, 0))
    println(divideTest(200, 5))
    println(divideTest(50, 25))
  }

  def divideTest(a: Int, b: Int): Double = {
    try {
      return divide(a, b)
    } catch {
      case e: AIsTooBig => -1
      case e: BIsTooBig => -2
      case e: ArithmeticException => -3
      case _ => 0
    }
  }

  def divide(a: Int, b: Int): Int = {
    if (a > 100) throw new AIsTooBig
    if (b > 10) throw new BIsTooBig
    return a / b
  }
}