Explanation of Scala basic Map Mapping

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# # Map

A Scala map (Map) is an object with a set of key / value pairs. The key is unique in the mapping, but the value is not necessarily unique. Mapping is also known as a hash table. There are two kinds of mappings, immutable and mutable. By default, Scala uses immutable mapping (Map). If you want to use mutable collections (Map), you need to explicitly import the scala.collection.mutable.Map class

Val map = Map ("name"-> "xiaoming", "age"-> 20) println (map ("name"))

To declare an empty mapping, you cannot omit the type description, add a key-value pair to the mapping (Map), and use the operator +

Var m: Map [String,Int] = Map () m + = ("one"-> 1)

To determine whether a value is included in the map, you can use the contains method

If (map.contains ("age")) {println (map ("age"))}

If you need to create a variable mapping, you need to introduce the scala.collection.mutable.Map package, otherwise value update is not a member of scala.collection.immutable.Map [String,Any] map ("gender") = "cumputer"

Val map = Map ("name"-> "xiaoming", "age"-> 20) map ("gender") = "cumputer" println (map ("gender")

Traversing map

Val map = Map ("name"-> "xiaoming", "age"-> 20) map ("gender") = "cumputer" for ((kmemv)