scala

scala-2.12.2 jiehua$ bin/scala
Welcome to Scala 2.12.2 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_112).
Type in expressions for evaluation. Or try :help.

scala> val stageIdToNumTasks = new HashMap[Int, Int]
<console>:11: error: not found: type HashMap
       val stageIdToNumTasks = new HashMap[Int, Int]
                                   ^

scala> import scala.collection.mutable.{ArrayBuffer, HashMap, HashSet, Queue}
import scala.collection.mutable.{ArrayBuffer, HashMap, HashSet, Queue}

scala> val stageIdToNumTasks = new HashMap[Int, Int]
stageIdToNumTasks: scala.collection.mutable.HashMap[Int,Int] = Map()

scala> stageIdToNumTasks(1)=11

scala> stageIdToNumTasks(2)=12

scala> stageIdToNumTasks(3)=13

scala> val stageIdToNumTasksTemp=stageIdToNumTasks.clone()
stageIdToNumTasksTemp: scala.collection.mutable.HashMap[Int,Int] = Map(2 -> 12, 1 -> 11, 3 -> 13)

scala> stageIdToNumTasks(4)=14

scala> println stageIdToNumTasks
<console>:13: error: value stageIdToNumTasks is not a member of Unit
       println stageIdToNumTasks
               ^

scala> stageIdToNumTasks.foreach(value => print(value + " "))
(2,12) (4,14) (1,11) (3,13)
scala> stageIdToNumTasksTemp.foreach(value => print(value + " "))
(2,12) (1,11) (3,13)
scala>

scala>

scala> case class Person(name: String, age: Int)
defined class Person

scala> val idToPerson = new HashMap[Int, HashMap[Int, Person]]
idToPerson: scala.collection.mutable.HashMap[Int,scala.collection.mutable.HashMap[Int,Person]] = Map()

scala> idToPerson(1) = HashMap(11=> Person(J, 20))
<console>:1: error: not a legal formal parameter.
Note: Tuples cannot be directly destructured in method or function parameters.
      Either create a single parameter accepting the Tuple1,
      or consider a pattern matching anonymous function: `{ case (param1, param1) => ... }
idToPerson(1) = HashMap(11=> Person(J, 20))
                        ^

scala> idToPerson(1) = HashMap(11 -> Person(J, 20))
<console>:16: error: not found: value J
       idToPerson(1) = HashMap(11 -> Person(J, 20))
                                            ^

scala> idToPerson(1) = HashMap(11 -> Person("Jin", 20))

scala> idToPerson(2) = HashMap(12 -> Person("Tin", 21))

scala> val test = idToPerson.clone
test: scala.collection.mutable.HashMap[Int,scala.collection.mutable.HashMap[Int,Person]] = Map(2 -> Map(12 -> Person(Tin,21)), 1 -> Map(11 -> Person(Jin,20)))

scala> idToPerson(3) = HashMap(13 -> Person("Qin", 22))

scala> idToPerson.foreach(value => print(value + " "))
(2,Map(12 -> Person(Tin,21))) (1,Map(11 -> Person(Jin,20))) (3,Map(13 -> Person(Qin,22)))
scala> test.foreach(value => print(value + " "))
(2,Map(12 -> Person(Tin,21))) (1,Map(11 -> Person(Jin,20)))
scala>