遍歷scala散列映射中給定鍵的值

Question

我需要檢查給定鍵的所有值以查看該值是否已經存在。通過下面的代碼，我總能得到最後一個值。如何迭代整個值列表？

val map = scala.collection.mutable.HashMap.empty[Int, String] 
map.put(0, "a") 
map.put(0, "b") 
map.put(0, "c") 
map.put(0, "d") 
map.put(0, "e") 
map.put(0, "f") 

for ((k, v) <- map) {println("key: " + k + " value: " + v)} 

輸出：

map: scala.collection.mutable.HashMap[Int,String] = Map() 
res0: Option[String] = None 
res1: Option[String] = Some(a) 
res2: Option[String] = Some(b) 
res3: Option[String] = Some(c) 
res4: Option[String] = Some(d) 
res5: Option[String] = Some(e) 

key: 0 value: f 
res6: Unit =() 

Answer 1

的關鍵是在一個HashMap唯一的。您不能爲同一個鍵擁有多個值。你可以做的是有一個HashMap[Int, Set[String]]並檢查值是否包含在裏面設置，或者甚至@TzachZohar指出簡單，一個MultiMap：

scala> import collection.mutable.{ HashMap, MultiMap, Set } 
import collection.mutable.{HashMap, MultiMap, Set} 

scala> val mm = new HashMap[Int, Set[String]] with MultiMap[Int, String] 
mm: scala.collection.mutable.HashMap[Int,scala.collection.mutable.Set[String]] with scala.collection.mutable.MultiMap[Int,String] = Map() 

scala> mm.addBinding(0, "a") 
res9: <refinement>.type = Map(0 -> Set(a)) 

scala> mm.addBinding(0, "b") 
res10: <refinement>.type = Map(0 -> Set(a, b)) 

scala> mm.entryExists(0, _ == "b") 
res11: Boolean = true