如何按其值对scala.collection.Map [java.lang.String，Int]进行排序?
问题描述：
如何将scala.collection.Map [java.lang.String，Int]按其值排序(在Int上也是如此)?简短而优雅的方法是什么?
How would you sort a scala.collection.Map[java.lang.String, Int] by its values (so on the Int)? What is a short and elegant way to do that?
答
取决于期望的输出集合类型是什么(SortedMap在键上排序)，您可以使用类似以下的东西:
Depending on what the expected output collection type is (SortedMaps are sorted on the keys), you could use something like this:
Map("foo"->3, "raise"->1, "the"->2, "bar"->4).toList sortBy {_._2}
结果将是按值排序的键/值对的列表:
Result would be the list of key/value pairs sorted by the value:
List[(java.lang.String, Int)] = List((raise,1), (the,2), (foo,3), (bar,4))
有一种地图类型保留了原始顺序，ListMap.如果应用此类型，则又有一张地图:
There is a Map type that retains the original order, ListMap, if you apply this, you have a map again:
import collection.immutable.ListMap
ListMap(Map("foo"->3, "raise"->1, "the"->2, "bar"->4).toList.sortBy{_._2}:_*)
那么你有:
scala.collection.immutable.ListMap[java.lang.String,Int] = Map((raise,1), (the,2), (foo,3), (bar,4))
(Scala 2.8)
(Scala 2.8)