Simplest way to sort list of objects

Question

I have a list of objects of type A. In a first iteration I assign each object a double value 0 < x < 1 and then want to sort each object according to it\'s x value.

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Answer 1

I go like this. For getting top c words in a hashmap:

  def getTopCWordsDeclarative(input: mutable.HashMap[String, Int], c: Int): Map[String, Int] = {
    val sortedInput = input.toList.sortWith(_._2 > _._2)
    sortedInput.take(c).toMap
  }

Answer 2

Use tuples instead of creating a new wrapper class.

List((1.2, "a1"), (0.1, "a2"), (0.9, "a3")).sorted
// List((0.1,a2), (0.9,a3), (1.2,a1))

Answer 3

You can actually do this quite easily with normal Scala lists and their sortBy method. Here's a brief REPL session showing how:

scala> class A(val value: Double) { override def toString = "A:" + value }
defined class A

scala> List(new A(6), new A(1), new A(3)) sortBy (_.value)
res0: List[A] = List(A:1.0, A:3.0, A:6.0)