map-additions-removals-operations.scala

val m = Map(
  (1, Order(1, "2017-01-01", 100, "COMPLETE")),
  (2, Order(2, "2017-01-01", 20, "CLOSED"))
)

//as m is immutable we cannot use +=, ++=, -= and --=
m + ((3, Order(3, "2017-01-01", 301, "PENDING")))
m + (3 -> Order(3, "2017-01-01", 301, "PENDING"))

//let us define m as mutable Map
val m = collection.mutable.Map(
  (1, Order(1, "2017-01-01", 100, "COMPLETE")),
  (2, Order(2, "2017-01-01", 20, "CLOSED"))
)

//Now we can manipulate map by using +=, ++=, -=, --=
m += ((3, Order(3, "2017-01-01", 301, "PENDING")))