Q1. Scala bytecode can run on top of Java VM. What is the fundamental difference between Java object.clone() and Scala object.copy()?

  •  One is a Java object, the other is a Scala object.
  •  clone() will copy class structures but not the data, while copy() will also copy data into new objects.
  •  There is no difference.
  •  copy() allows you to change values during the copying process; clone() does not.

Q2. What value does this code return?

val m1 = Map("a"->1,"b"->2,"c"->3)
  •  a
  •  2
  •  b
  •  1

Q3. What is one way to avoid low-level parallelization details?

  •  monads
  •  literal functions
  •  partially applied functions
  •  parallel collections

Q4. What do you use in ScalaTest to see a detailed diagram of error messages when a test fails?

  •  ArgumentExceptions
  •  AssertionException
  •  DiagrammedAssertions
  •  JUnit

Q5. What data type would you use to store an immutable collection of objects that contain a fixed number of varying types?

  •  Array
  •  ImmutableCollection
  •  List
  •  Tuple

Q6. After defining a function in the interpreter, Scala returns the following. What does the () indicate?

myfnc: ()Unit
  •  The function has no side effects.
  •  The function takes no parameters.
  •  The function returns no value.
  •  Returning unit types to the function is a closures.

Q7. What type of number is 1234.e5?

  •  hexadecimal
  •  short
  •  floating point
  •  long

Q8. When you convert a map to a list using the toList method of the map, the result will be of which type?

  •  List[(String, String)]
  •  List[(Array, Array)]
  •  List[(Collection, Collection)]
  •  List

Q9. What type of object does this code create?

val x = (1234, "Active")
  •  List
  •  Map
  •  Tuple
  •  Array

Q10. Which is a subclass of all classes?

  •  AnyVal
  •  AnyRef
  •  Method
  •  Null

ReferenceNull in Scala Standard library. The question is a bit incorrect - Null is a subtype of every type except those of value classes

Q11. For the for-yield construct, is the scope separate between for-body and yield-body?

  •  Yes and no. It is different depending on the for construct and what it does.
  •  Yes, because the for section does not expose its scope.
  •  No, because for-yield shares the same scope, even though they are within separate curly braces.
  •  Yes, because they are within different curly braces.

Example: yield-body has access to the e variable from the for-body

val a = Array(1, 2, 3, 4, 5)
for {
     e <- a if e > 2
} yield e

Q12. What is one way to implement pattern matching on methods?

  •  using regex
  •  using monads
  •  using string matching
  •  using case classes

Note: ambiguous question, it's not clear what kind of pattern matching is meant here.

Q13. What is the value of z after executing this code?

val y = List('a','b')
val z = y::List('c')
  •  List(a,b,c)
  •  List(List(a, b), c)
  •  List(c,a,b)
  •  List(c,List(a,b))

Q14. What term is used to specify a precondition?

  •  assert
  •  require
  •  precondition
  •  mustHave

Q15. Which Scala type may throw an exception or a successfully computed value, and is commonly used to trap and propagate errors?

  •  scala.util.ExceptionHandling
  •  scala.Catch.Throw
  •  scala.exception.TryFinally
  •  scala.util.Try


Q16. What is the data type of y after this code is executed?

val y = (math floor 3.1415 * 2)
  •  short
  •  double
  •  int
  •  bigInt

Q17. When using pattern matching, which character matches on any object?

  •  %
  •  _
  •  ^
  •  -

ReferencePattern Matching

Q18. You have created an array using val. Can you change the value of any element of the array—and why or why not?

  •  Yes, the reference to the array is immutable, so the location that the array points to is immutable. The values in the array are mutable.
  •  The 0th element is immutable and cannot be modified. All other elements can be modified.
  •  Yes, val does not make arrays immutable.
  •  No, val makes the array and values of the array immutable.


val a1 = Array(1, 2, 3)
a1{1} = 3 // OK
a1 = Array(1, 3, 3) // error: reassignment to val

Q19. What is the output of this function?

def main () {
     var a = 0
     for (a<-1 until 5){println(a)}
  •  1,2,3,4,5
  •  0,1,2,3,4
  •  1,2,3,4
  •  2,3,4,5

Q20. What do you call objects with immutable state?

  •  singletons
  •  stationary objects
  •  functional objects
  •  fixed objects

Note: singletons may have mutable state

Q21. You have written a Scala script. How would you access command-line arguments in the script?

  •  use array named args
  •  use tuple named args
  •  use numbered variables with a _ prefix for example _ 1, _ 2, _ 3
  •  use numbered variables with a $ prefix - for example $1, $2, $3

Q22. What does this code return? val x = 3; if (x > 2) x = 4 else x = x*2

  •  4
  •  an error
  •  6
  •  3

Q23. Which statement returns a success or a failure indicator when you execute this code?

val MyFuture = Future {runBackgroundFunction() }

  •  myFuture.onComplete
  •  myFuture(status)
  •  myFuture.Finished
  •  complete(myFuture)

Q24. To denote a parameter that may be repeated, what should you place after type?

  •  %
  •  &
  •  _
  •  -

Q25. What is called when a superclass has more than one subclass in Scala?

  •  polyinheritance
  •  multilevel inheritance
  •  multimode inheritance
  •  hierarchical inheritance

Q26. One way to improve code reliability is to use __ , which will evaluate a condition and return an error if the condition is violated.

  •  packages
  •  polymorphisms
  •  assertions
  •  traits

Q27. Which statement about if-else-if-else statements is true?

  •  If the first else-if does not succeed, then no other else-ifs are tested.
  •  If an else-if does not succeed, then none of the remaining else-if statements or elses will be tested.
  •  All else-if statements are tested in all cases.
  •  If an else-if succeeds, then none of the remaining else-if statements or elses will tested.

Q28. What do you call the process of changing the definition of an inherited method?

  •  recursive methods
  •  currying methods
  •  redefining methods
  •  overriding methods

Q29. To denote a parameter that may be repeated, what should you place after the type?

  •  _
  •  *
  •  %
  •  &

ReferenceRepeated Parameters in Scala

Q30. What is the code below equivalent to?

myClass.foreach(println _)
  •  myClass.foreach(println ())
  •  myClass.foreach(print NIL)
  •  myClass.loop(println ())
  •  myClass.foreach(x => println(x))

Q31. What is an advantage of an immutable object?

  •  Immutable objects use less memory than their mutable counterparts.
  •  Immutable objects do not require error handling.
  •  Immutable objects can be used in classes, mutable objects cannot.
  •  Immutable objects are threadsafe.

Q32. You want to create an iteration loop that tests the condition at the end of the loop body. Which iteration would you use?

  •  do-while loop
  •  while loop
  •  for loop
  •  do-until loop

Q33. What can you use to make querying a database more efficient, by avoiding the need to parse the SQL string every time a query is executed from Scala?

  •  database driver
  •  connection
  •  prepared statement
  •  SQL view

ReferencePreparedStatement from Java which is also used in Scala

Q34. Which is not a member of the collections hierarchy?

  •  Set
  •  Seq
  •  Hash
  •  Map

Q35. Which term makes the contents of packages available without prefixing?

  •  use
  •  include
  •  import
  •  assertion

Q36. If you wanted to find the remainder after division, what operator would you use?

  •  %
  •  DIV
  •  //
  •  /

Q37. What are defined inside a class definition?

  •  method
  •  fields and methods
  •  fields, methods, and packages
  •  fields

Q38. What defines methods and fields that can then be reused by mixing into classes?

  •  singleton
  •  assertion
  •  trait
  •  monad

Q39. When do you need to explicitly state the return type in a function definition?

  •  when the function has no side effects
  •  when the function returns a Unit type
  •  when the function is recursive
  •  when the function has side effects

Q40. Why would you make a field private?

  •  so only methods in the same file can access the field
  •  so only methods in the same package can access the field
  •  so only methods in the same class could access the field
  •  so only methods defined in a Java class can access the field

Q41. What's the difference between .equals and ==?

  •  They do the exact same thing
  •  == won't work on objects
  •  == cannot be applied to String
  •  == is a wrapper of .equals() and checks for nulls


Q42. What is denotes the intersection between two sets?

  •  ||
  •  &&
  •  &
  •  %


Q43. What's the best way to execute code in the background in a separate thread?

  •  AltFuture
  •  Future
  •  AltProcess
  •  AltThread

Q44. What do you call a function defined in a block?

  •  private function
  •  block function
  •  local function
  •  method

Q45. What do you call a Scala method that is parametrized by type as well as by value?

  •  multimode method
  •  polymorphic method
  •  closure
  •  collection method

Q46. What type of exception is thrown when a precondition is violated?

  •  IllegalArgumentException
  •  NumberFormatException
  •  NullPointerExcepetion
  •  MalformedParameterException

Q47. In scala what is precondition?

  •  a constraint on where a method may be called from
  •  a constraint on values passed to a methode constructor
  •  a class of predifined error messages
  •  a class of Boolean operators

Q48. What would you change in this code to make it execute in parallel?

 val myNums = (1 to 500).toList + 1)
  •  Change to
  •  Change toList to toListPar
  •  Change val to val.par
  •  Change toList to toParallelList

Q49. What is a free variable?

  •  a variable defined outside a function
  •  a variable referenced in a function that is not assigned a value by that function
  •  a variable that has a global scope
  •  a variable defined in a class and available to all methods in that class

Q50. What is the difference between .equals() and == ?

  •  == is wrapper of .equals() and checks for Nulls
  •  They do the exact same thing.
  •  == cannot be applied to String.
  •  == won't work on objects

Q51. What's the best way to execute code in the background in a separate thread?

  •  AltThread
  •  AltFuture
  •  AltProcess
  •  Future