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scala-quiz.md

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Scala

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)
m1("a")
  • 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

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[(Array, Array)]
  • 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 NOT SURE

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. NOT SURE
  • 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.

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

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

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?

answers missing

Answer should be Option: Some or None

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?

  • %
  • \_
  • ^
  • -

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.

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

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