التجميع والترتيب

تنظيم البيانات

object Main {
  def main(args: Array[String]): Unit = {
    val nums = List(5, 3, 8, 1, 9, 2)
    println(nums.sorted)
  }
}

sorted: الترتيب الطبيعي

object Main {
  def main(args: Array[String]): Unit = {
    println(List(3, 1, 2).sorted)
    println(List("pear", "apple", "fig").sorted)
  }
}

sortBy: الفرز حسب مفتاح

object Main {
  def main(args: Array[String]): Unit = {
    val words = List("banana", "fig", "apple")
    val byLength = words.sortBy(_.length)
    println(byLength)
  }
}

الفرز ترتيبًا تنازليًا

object Main {
  def main(args: Array[String]): Unit = {
    val nums = List(5, 3, 8, 1)
    println(nums.sortBy(-_))
    println(nums.sorted(Ordering.Int.reverse))
  }
}

sortWith: مُقارِن مخصّص

object Main {
  def main(args: Array[String]): Unit = {
    val nums = List(5, 3, 8, 1)
    val descending = nums.sortWith((a, b) => a > b)
    println(descending)
  }
}

الفرز حسب مفاتيح متعددة

object Main {
  def main(args: Array[String]): Unit = {
    val people = List(("Ann", 30), ("Bob", 25), ("Ann", 22))
    val sorted = people.sortBy { case (name, age) => (name, age) }
    println(sorted)
  }
}

groupBy: التقسيم إلى Map

object Main {
  def main(args: Array[String]): Unit = {
    val nums = List(1, 2, 3, 4, 5, 6)
    val byParity = nums.groupBy(_ % 2 == 0)
    println(byParity)
  }
}

التجميع حسب مفتاح محسوب

object Main {
  def main(args: Array[String]): Unit = {
    val words = List("apple", "avocado", "banana", "cherry", "cranberry")
    val byFirstLetter = words.groupBy(_.head)
    byFirstLetter.foreach { case (letter, ws) => println(s"$letter -> $ws") }
  }
}

تحويل المجموعات

object Main {
  def main(args: Array[String]): Unit = {
    val words = List("cat", "car", "dog", "deer", "cow")
    val counts = words.groupBy(_.head).view.mapValues(_.size).toMap
    println(counts)
  }
}

groupMapReduce في خطوة واحدة

object Main {
  def main(args: Array[String]): Unit = {
    val sales = List(("books", 10), ("toys", 5), ("books", 7), ("toys", 3))
    val totals = sales.groupMapReduce(_._1)(_._2)(_ + _)
    println(totals)
  }
}

دمج التجميع والفرز

object Main {
  def main(args: Array[String]): Unit = {
    val words = List("apple", "avocado", "banana", "cherry", "cranberry", "apricot")
    val ranked = words
      .groupBy(_.head)
      .view.mapValues(_.size).toList
      .sortBy(-_._2)
    println(ranked)
  }
}

اختبار سريع

مراجعة