scala进阶3-视图界定view bounds

最新推荐文章于 2024-02-23 10:09:22 发布

dingyuanpu

最新推荐文章于 2024-02-23 10:09:22 发布

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/**
  * "<%" 视图界定, 背后有隐式转换,如将Int变成了RichInt
  * @param first
  * @param second
  * @param ev$1
  * @tparam T
  */
class Pair_NotPerfect[T <% Comparable[T]](val first: T, val second: T) {
  def bigger = if(first.compareTo(second) > 0) first else second
}

//这种写法更好
class Pair_Better[T <% Ordered[T]](val first: T, val second: T) {
  def bigger = if(first > second) first else second
}

object View_Bounds {
  def main(args: Array[String]): Unit = {
    val pair = new Pair_NotPerfect("Spark", "Hadoop")
    println(pair.bigger)

    val pairInt = new Pair_NotPerfect(3, 5) // Int -> RichInt
    println(pairInt.bigger)

    val pair_better_string = new Pair_Better("Java", "Scala") //String  -> RichString
    println(pair_better_string.bigger)

    val pair_better_int = new Pair_Better(20, 30)
    println(pair_better_int.bigger)
  }
}