absoverride.scala

来自「JAVA 语言的函数式编程扩展」· SCALA 代码 · 共 38 行

abstract class AbsIterator {
  type T
  def hasNext: boolean
  def next: T
}
trait RichIterator extends AbsIterator {
  def foreach(f: T => unit): unit = 
    while (hasNext) f(next)
}
class StringIterator(s: String) extends AbsIterator {
  type T = char
  private var i = 0
  def hasNext = i < s.length()
  def next = { val x = s.charAt(i); i = i + 1; Console.println("next: " + x); x }
}
trait SyncIterator extends AbsIterator {
  abstract override def hasNext: boolean = 
    synchronized(super.hasNext)
  abstract override def next: T = 
    synchronized {
      Console.println("<sync>"); val x = super.next; Console.println("</sync>"); x
    }
}
trait LoggedIterator extends AbsIterator {
  abstract override def next: T = { 
    val x = super.next; Console.println("log: " + x); x 
  }
}
class Iter2(s: String) extends StringIterator(s) 
               with SyncIterator with LoggedIterator;         
object Test {
  def main(args: Array[String]): unit = {
    class Iter extends StringIterator(args(0)) with RichIterator with SyncIterator with LoggedIterator
    val iter = new Iter
    iter foreach Console.println 
  }
}