Search code examples
multithreadingscalacollectionsdictionarythread-safety

Scala - Mutable thread safe collections


I need a mutable thread safe Map and a mutable thread safe List in Scala. I know that the immutable collections are thread safe by default. But, I need to update my collections very often because of which I couldn't use immutable. Also I need my threadsafe mutable Map to maintain the insertion order.

Right now am using the map below

val map = scala.collection.mutable.LinkedHashMap[String,Any]()

This map maintains the insertion order and is mutable. How do I make it thread safe?


Solution

  • As was mentioned by AlexIv in his answer, there's a trait you can mix in if you want thread safety. There's another way though:

        val synchronizedMap = new scala.collection.mutable.LinkedHashMap[String, Any]() with scala.collection.mutable.SynchronizedMap[String, Any]
    

    That should give you the map with synchronization on each access. Easy, but might not meet the performance requirements. If so, it would be probably easier to create a custom class extending the LinkedHashMap, mixing in the concurrent.Map trait (as was suggested) and provide the implementation of relevant methods, i.e: putIfAbsent, remove replace (2 overloads).