How to find the number of (key , value) pairs in a map in scala?

问题

I need to find the number of (key , value) pairs in a Map in my Scala code. I can iterate through the map and get an answer but I wanted to know if there is any direct function for this purpose or not.

回答1:

you can use .size

scala> val m=Map("a"->1,"b"->2,"c"->3)
m: scala.collection.immutable.Map[String,Int] = Map(a -> 1, b -> 2, c -> 3)

scala> m.size
res3: Int = 3

回答2:

Use Map#size:

The size of this traversable or iterator.

The size method is from TraversableOnce so, barring infinite sequences or sequences that shouldn't be iterated again, it can be used over a wide range - List, Map, Set, etc.

来源：https://stackoverflow.com/questions/24952447/how-to-find-the-number-of-key-value-pairs-in-a-map-in-scala