Vfrdtyky

Following code throws exception after inserting 483180000 values. Is this expected. Is there any way to add more than a billion values into a mutable HashSet in Scala. Tried this code with Scala versions 2.11 and 2.12. Both versions throw same exception.

import scala.collection.mutable.HashSet



object TestApp extends App {

    val hs = HashSet[Int]()

    for (i <- 1 to Int.MaxValue) {

        hs += i

    }

}



java.lang.NegativeArraySizeException

        at scala.collection.mutable.FlatHashTable.growTable(FlatHashTable.scala:218)

        at scala.collection.mutable.FlatHashTable.addEntry(FlatHashTable.scala:160)

        at scala.collection.mutable.FlatHashTable.addEntry$(FlatHashTable.scala:148)

        at scala.collection.mutable.HashSet.addEntry(HashSet.scala:39)

        at scala.collection.mutable.FlatHashTable.addElem(FlatHashTable.scala:140)

        at scala.collection.mutable.FlatHashTable.addElem$(FlatHashTable.scala:139)

        at scala.collection.mutable.HashSet.addElem(HashSet.scala:39)

        at scala.collection.mutable.HashSet.$plus$eq(HashSet.scala:58)

        at alice.grid.collection.TestApp$.$anonfun$new$2(TestApp.scala:12)

        at scala.collection.immutable.Range.foreach$mVc$sp(Range.scala:155)

        at alice.grid.collection.TestApp$.delayedEndpoint$alice$grid$collection$TestApp$1(TestApp.scala:11)

        at alice.grid.collection.TestApp$delayedInit$body.apply(TestApp.scala:5)

        at scala.Function0.apply$mcV$sp(Function0.scala:34)

        at scala.Function0.apply$mcV$sp$(Function0.scala:34)

        at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)

        at scala.App.$anonfun$main$1$adapted(App.scala:76)

        at scala.collection.immutable.List.foreach(List.scala:388)

        at scala.App.main(App.scala:76)

        at scala.App.main$(App.scala:74)

        at alice.grid.collection.TestApp$.main(TestApp.scala:5)

        at alice.grid.collection.TestApp.main(TestApp.scala)

        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

        at java.lang.reflect.Method.invoke(Method.java:498)

No, there is no way, how to add that many items. If you check the source code at (FlatHashTable.scala:218), you will find:

table = new Array[AnyRef](table.length * 2)

lenth is an integer. At certain point, multiplying it by two will cause an overflow and the result is a negative number. Java does not allow to create an array with size specified by negative number.

This is simply a limitation imposed by implementation of the HashSet.