If you want to view the content of a RDD, one way is to use collect(): myRDD.collect().foreach(println) That’s not a good idea, though, when the RDD has billions of lines. Use take() to take just a few to print out: myRDD.take(n).foreach(println)
My favorite example: case class Board(length: Int, height: Int) { case class Coordinate(x: Int, y: Int) { require(0 <= x && x < length && 0 <= y && y < height) } val occupied = scala.collection.mutable.Set[Coordinate]() } val b1 = Board(20, 20) val b2 = Board(30, 30) val c1 = b1.Coordinate(15, 15) val c2 … Read more
Select expression and type Alt + =. If you want to change the shortcut go to Preferences > Keymap and enter “Type Info” in the search field. In older versions, it’s Shift + Ctrl + Alt + T.
The compiler knows more information about types than the JVM runtime can easily represent. A Manifest is a way for the compiler to send an inter-dimensional message to the code at runtime about the type information that was lost. It isn’t clear if a Manifest would benefit the errors you are seeing without knowing more … Read more
bar: Int This is barely a constructor parameter. If this variable is not used anywhere except the constructor, it remains there. No field is generated. Otherwise private val bar field is created and value of bar parameter is assigned to it. No getter is created. private val bar: Int Such declaration of parameter will create … Read more
scala> println (Nil == List()) true scala> println (Nil eq List()) true scala> println (Nil equals List()) true scala> System.identityHashCode(Nil) 374527572 scala> System.identityHashCode(List()) 374527572 Nil is more idiomatic and can be preferred in most cases. Questions?
By using partition method: scala> List(1,2,3,4).partition(x => x % 2 == 0) res0: (List[Int], List[Int]) = (List(2, 4),List(1, 3))
You can use scala.math.BigDecimal: BigDecimal(1.23456789).setScale(2, BigDecimal.RoundingMode.HALF_UP).toDouble There are a number of other rounding modes, which unfortunately aren’t very well documented at present (although their Java equivalents are).
First, they are all non-strict. That has a particular mathematical meaning related to functions, but, basically, means they are computed on-demand instead of in advance. Stream is a lazy list indeed. In fact, in Scala, a Stream is a List whose tail is a lazy val. Once computed, a value stays computed and is reused. … Read more
There’s a very convenient -jvm-debug flag in the official SBT packages for Mac, Linux & Windows. You can use the flag to specify the debug port: sbt -jvm-debug 5005 Under the covers, this starts the JVM for SBT with the typical verbose debugging incantation: -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5005 You now can run your code as normal, for … Read more