Scala计算Map中元素的出现次数

Question

我如何计算地图中元素的出现次数？

例

val myMap = Map("word1" -> "foo", "word3" -> "word4", "word5" -> "foo")

myMap contains "foo" count //???
// returns 2

Answer 1

你可以使用count谓词:

myMap.count({ case (k, v) => v == "word1" })

或者:

myMap.values.count(_ == "word1")

甚至:

myMap.count(_._2 == "word1") // _2 is the second tuple element

注意:这是值,而不是键.钥匙是独一无二的