How does Scala's mutable Map update [map(key) = newValue] syntax work?

Question

I\'m working through Cay Horstmann\'s Scala for the Impatient book where I came across this way of updating a mutable map.

scala> val scores = scala.coll         


        

Answer 1

The problem is you're trying to update immutable map. I had the same error message when my map was declared as

var m = new java.util.HashMap[String, Int]

But when i replaced the definition by

var m = new scala.collection.mutable.HashMap[String, Int]

the m.update worked.