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?
Fast hint for those coming to this in 2018 or later:
import java.util.concurrent.ConcurrentHashMap
val m: ConcurrentHashMap[String,MyClass] = new ConcurrentHashMap
java.util.concurrent. package.
Commented
Jul 25, 2022 at 21:15
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).
synchronized method on the mutable collection directly where you need thread safety. It'll save you the performance hit that this mixin brings. E.g. someMap.synchronized { someMap += ("someKey", "anyValue") }
java.util.concurrent.ConcurrentHashMap as an alternative."
Commented
Nov 8, 2017 at 22:13
To elaborate on the comment for a Map you can use
import scala.collection.concurrent.TrieMap
Is not deprecated and is mutable and thread-safe.
It should drop in for your scala.collection.mutable.LinkedHashMap as they share the same interface of scala.collection.mutable.MapLike and scala.collection.mutable.Map
Sadly I don't know about the List
