快学Scala 第五课（构造映射，获取映射值，更新映射值，迭代映射，与Java互操作）

提示：扫一扫查出行
【扫一扫了解最新限行尾号】
复制提示

构造映射：

val score = Map[String, Int]()
val score1 = HashMap[String, Int]() val value1 = Map[String, Int]("aa" -> 1, "bb" -> 2)
val value2 = Map[String, Int](("aa", 1), ("bb", 2))

获取映射值：

println(if(value2.contains("cc")) value2("cc") else 0)
println(value2.getOrElse("cc", 0))
println(value2.getOrElse("aa", 0))

更新映射值：

score1("aa") = 1
score1("bb") = 2
score1 += ("cc" -> 3, "dd" -> 4)
score1 += (("cc", 3), ("dd", 4))
score1 -= "cc"

迭代映射：

for((k,v) <- value2){
println(k)
println(v)
} value2.keySet
println(value2.values) for (v <- value2.values) println(v) println(for ((k, v) <- value2 ) yield {(v, k)})

与Java互操作：(java.util.Properties 转 scala.collection.mutable.Map)

val prop = new Properties()
prop.put("aaa", "1")
prop.put("bba", "2") import scala.collection.JavaConversions.propertiesAsScalaMap
val scalaMap: scala.collection.mutable.Map[String, String] = prop
scalaMap.foreach(println)