Scala - Initialize an empty mutable SynchronizedHashMap

Question

From what I understand, we can initialize an empty mutable HashMap as

var keyCountsMap :scala.collection.mutable.Map[Any, Int] = scala.collection.mutable.Map[Any, Int]()

But how do I initialize this HasMap as synchronized ? I tried

var keyCountsMap :scala.collection.mutable.SynchronizedMap[Any, Int] = scala.collection.mutable.Map[Any, Int]()

but it I get the following error:

type mismatch; found : scala.collection.mutable.Map[Any,Int]
required: scala.collection.mutable.SynchronizedMap[Any,Int]

Answer 1

您可以混合SynchronizedMap（deprecated in 2.11）

    var keyCountsMap = new scala.collection.mutable.HashMap[Any, Int]() with scala.collection.mutable.SynchronizedMap[Int, Int]

Answer 2

如果您查看文档，您会看到：

  

此类应用作 mixin 。它同步Map   它所混入的类的函数。

和

  

通过traits同步已被弃用，因为它本身就是这样   不可靠的。将 java.util.concurrent.ConcurrentHashMap 视为一个   替代品。