scala基础 -- map

Posted 2022-08-22 pocahontas

 

creates Map

val weights = Map("cat" -> 10, "elephant" -> 200000)
val weight = weights("elephant")
println(weight)

 

val colors = Map(("bird", "blue"), ("fox", "red"))
val result1 = colors("bird")
println(result1)

 adds key, value to map

val zoo = Map("frog" -> 1, "lion" -> 1)
val all = zoo + ("zebra" -> 1)

 

iterate over all values.

zoo.keys.foreach(println(_))
for (value <- zoo.values) 
    println(value)

 

getOrElse

// Use a default value if the key does not exist.
val result3 = sizes.getOrElse("Small", 0)
if (result3 == 0) 
    println("Zero, else value")

 

val result2 = sizes.get("Large")
if (result2.isDefined) 
    println(result2)
    val number = result2.get
    println(number)

 equals

val map1 = Map((10, true), (20, false))
val map2 = Map((20, false), (10, true))
val map3 = Map((20, true), (10, true))

// These two maps are structurally equal.
if (map1.equals(map2)) 
    println("Maps equal")

 Output

Maps equal