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Basic Scala MCQ

1. 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))

Answer

Correct Answer: List(List(a, b), c)

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2. Q2. What value does this code return? val m1 = Map("a"->1,"b"->2,"c"->3) m1("a")

Answer

Correct Answer: 1

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3. What value does this code return? x= List(1,2,4); x(1)?

(1,2,4)

Nil

Answer

Correct Answer: 2

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

AltThread

AltFuture

AltProcess

Future

Answer

Correct Answer: Future

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5. 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

Answer

Correct Answer: A variable defined outside a function

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

Val myNums = (1 to 500).toList

List.map(_ + 1)

Change list.map to list.par.map.

Change toList to toListPar

Change val to val.par

Change toList to toParallelList

Answer

Correct Answer: Val myNums = (1 to 500).toList

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7. 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

Answer

Correct Answer: A class of predifined error messages

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

IllegalArgumentException

NumberFormatException

NullPointerExcepetion

MalformedParameterException

Answer

Correct Answer: IllegalArgumentException

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9. What is denotes the intersection between two sets?

Answer

Correct Answer: &

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10. 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

Answer

Correct Answer: == is a wrapper of .equals() and checks for nulls

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11. 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

Answer

Correct Answer: So only methods in the same class could access the field

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12. 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

Answer

Correct Answer: When the function is recursive

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

Singleton

Assertion

Trait

Monad

Answer

Correct Answer: Trait

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14. What are defined inside a class definition?

Method

Fields and methods

Fields, methods, and packages

Fields

Answer

Correct Answer: Fields and methods

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

DIV

Answer

Correct Answer: %

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

Use

Include

Import

Assertion

Answer

Correct Answer: Import

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

Set

Seq

Hash

Map

Answer

Correct Answer: Hash

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18. 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

Answer

Correct Answer: Prepared statement

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19. 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

Answer

Correct Answer: Do-while loop

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20. 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.

Answer

Correct Answer: Immutable objects are threadsafe.

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21. 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))

Answer

Correct Answer: MyClass.foreach(x => println(x))

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

Answer

Correct Answer: *

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

Recursive methods

Currying methods

Redefining methods

Overriding methods

Answer

Correct Answer: Overriding methods

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24. 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.

Answer

Correct Answer: If an else-if succeeds, then none of the remaining else-if statements or elses will tested.

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25. 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

Answer

Correct Answer: Assertions

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

Polyinheritance

Multilevel inheritance

Multimode inheritance

Hierarchical inheritance

Answer

Correct Answer: Hierarchical inheritance

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

Answer

Correct Answer: -

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28. 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)

Answer

Correct Answer: MyFuture.onComplete

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

An error

Answer

Correct Answer: An error

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30. 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

Answer

Correct Answer: Use array named args

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31. What do you call objects with immutable state?

Singletons

Stationary objects

Functional objects

Fixed objects

Answer

Correct Answer: Functional objects

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32. 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.

Answer

Correct Answer: 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.

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

Answer

Correct Answer: _

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34. What is the data type of y after this code is executed? val y = (math floor 3.1415 * 2)

Short

Double

Int

BigInt

Answer

Correct Answer: Double

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35. 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

Answer

Correct Answer: Scala.util.Try

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36. What term is used to specify a precondition?

Assert

Require

Precondition

MustHave

Answer

Correct Answer: Assert

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37. 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.

Answer

Correct Answer: No, because for-yield shares the same scope, even though they are within separate curly braces.

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38. Which is a subclass of all classes?

AnyVal

AnyRef

Method

Null

Answer

Correct Answer: Null

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39. What type of object does this code create? val x = (1234, "Active")

List

Map

Tuple

Array

Answer

Correct Answer: Tuple

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40. 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

Answer

Correct Answer: List

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41. What type of number is 1234.e5?

Hexadecimal

Short

Floating point

Long

Answer

Correct Answer: Floating point

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42. 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.

Answer

Correct Answer: The function returns no value.

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43. 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

Answer

Correct Answer: Tuple

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

ArgumentExceptions

AssertionException

DiagrammedAssertions

JUnit

Answer

Correct Answer: DiagrammedAssertions

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

Monads

Literal functions

Partially applied functions

Parallel collections

Answer

Correct Answer: Parallel collections

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46. 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.

Answer

Correct Answer: Copy() allows you to change values during the copying process; clone() does not.

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47.
Despite using the same code, the different browser and database modules created really are separate modules. This means that each module has its own contents, including any nested classes. Which of the following options is described by the above statements?

Tracking module instances

Splitting modules into traits

Multiple modules into traits

Database modules into traits

Answer

Correct Answer: Tracking module instances

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48.
Regex class is available in the ........................ package.

scala.util.match

scala.util.matching

scala.utils.matching

Answer

Correct Answer: scala.util.matching

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49.
Which of the following is false about Case Class?

Case classes can not be initialised

Case class instances can be constructed without using new keyword

All constructor arguments of case classes are accessible from outside using automatically generated accessor functions

Pattern matching can be performed on case classes

Answer

Correct Answer: Case classes can not be initialised

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50.
Choose the correct statement that describes an 'abstract sealed' class?

sealed classes can not be extended

sealed classes can always be extended

sealed classes can be extended in the same Scala package

sealed classes can be extended in the same file

Answer

Correct Answer: sealed classes can be extended in the same file

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51.
Scala is ................ with Java. The two languages are interoperable with each other.

compatible

runtime

library

None of the above

Answer

Correct Answer: compatible

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52.
Choose the correct statements that describe a Scala Case class?

Case class objects are used to implement complex behaviour

Case class objects are immutable

Case class instances can be created with a compact syntax

Case class objects have default implicit constructors

Answer

Correct Answer: Case class objects are used to implement complex behaviour
Case class instances can be created with a compact syntax

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53.
Which of the following describe using Scala class that is defined in a package object from Java?

com/mycompany/test/MyTest.class com/mycompany/test/package.class com/mycompany/test/package$.class

package com.mycompany package object test { val foobar = 42 } package test { class MyTest { def foo(): Int = { 42 } } }

com/mycompany/test/package.class com/mycompany/test/package$.class com/mycompany/test/package$MyTest.class

package com.mycompany package object test { class MyTest { scala> foo(): Int = { 42 } } }

Answer

Correct Answer: com/mycompany/test/MyTest.class com/mycompany/test/package.class com/mycompany/test/package$.class
package com.mycompany package object test { val foobar = 42 } package test { class MyTest { def foo(): Int = { 42 } } }

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54.
Often a module is too large to fit comfortably into a single file. When that happens, you can use traits to split a module into separate files. Which of the following is described by the above statement?

Abstraction modules into traits

Splitting modules into traits

Tracking modules into traits

All of the above

Answer

Correct Answer: Splitting modules into traits

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55.
Which of the following is not valid in Scala?

lazy var = 10

def x = 10

val (x,y) = (10,20)

var x = 10

Answer

Correct Answer: lazy var = 10

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56.
When Extractor object is using the match statement, the unapply method will be __ executed.

automatically

automatic

manual

manually

Answer

Correct Answer: automatically

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57.
Which one of the following options is equivalent to the code below? for { x <- 1 to 10 y <- 1 to 10 } yield (x,y)

(1 to 10).map( x => (1 to 10).flatMap(y => (x,y)))

(1 to 10).map( x => (1 to 10).map(y => (x,y)))

(1 to 10).flatMap( x => (1 to 10).map(y => (x,y)))

Answer

Correct Answer: (1 to 10).flatMap( x => (1 to 10).map(y => (x,y)))

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58.
Which of the following are types of function in Scala?

Int => String

(Int,Int) => Int

Int => Int => Int

(Int => Int) => Int

All of the above

Answer

Correct Answer: All of the above

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59.
Which of the following statement is about Scala anonymous function?

In a source code, anonymous functions are called ‘function literals’ and at run time, function literals are instantiated into objects called function values. Scala provides a relatively easy syntax for defining anonymous functions.

anonymous is the technique of transforming a function that takes multiple arguments into a function that takes a single argument Many of the same techniques as language like Haskell and LISP are supported by Scala. Function currying is one of the least used and misunderstood one.

A anonymous is a function whose return value depends on the value of the variables declared outside the function.

anonymous is an object functional programming and scripting language for general software applications designed to express solutions in a concise manner.

Answer

Correct Answer: In a source code, anonymous functions are called ‘function literals’ and at run time, function literals are instantiated into objects called function values. Scala provides a relatively easy syntax for defining anonymous functions.

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60.
How to return a value from a scala function?

private def checkValu() : Option[Integer] = { if(!list.isEmpty()){ for(value <-list){ val x = list.get(0) } } return (x) }

public def checkValu() : Option[Integer] = { if(!list.isEmpty()){ for(value <-list){ val x = list.get(0) } } return (x) }

None of the above

Answer

Correct Answer: private def checkValu() : Option[Integer] = { if(!list.isEmpty()){ for(value <-list){ val x = list.get(0) } } return (x) }
private def checkValu() : Option[Integer] = { if(!list.isEmpty()){ for(value <-list){ val x = list.get(0) } } return (x) }

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61.
Which of the following one is Accessing scala object fields from java?

public class JavaTest { public static void main(String[] args) { int i = TestObject.field(); } }

public class JavaTest { public static void main(String[] args) { int i = TestObject.field; } }

Both of the above

None

Answer

Correct Answer: public class JavaTest { public static void main(String[] args) { int i = TestObject.field(); } }

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62.
Which of the following are functional trio in Scala?

filter

map

reduce (foldLeft + foldRight)

None of the above

Answer

Correct Answer: filter
map
reduce (foldLeft + foldRight)

Note: This question has more than 1 correct answers

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63.
This trait consists of which of the following methods?

isEqual

isNotEqual

Point

Both 1 and 2

Answer

Correct Answer: Both 1 and 2

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64.
If you want to compare two objects to see if they are equal, you should usually use either ==, or its inverse !=. Which of the following code is true?

scala> 1 == 2 res24: Boolean = false scala> 1 != 2 res25: Boolean = true scala> 2 == 2 res26: Boolean = true

scala> 1 == 2 res24: Boolean = true scala> 1 != 2 res25: Boolean = flase scala> 2 == 2 res26: Boolean = true

scala> 1 == 2 res24: Boolean = true scala> 1 != 2 res25: Boolean = true scala> 2 == 2 res26: Boolean = false

Answer

Correct Answer: scala> 1 == 2 res24: Boolean = false scala> 1 != 2 res25: Boolean = true scala> 2 == 2 res26: Boolean = true

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65.
Which of the following are function Literal's in Scala?

“World” filter { c => c > 50 }

“World” filter { _ > 50 }

“World” filter ( _ > 50 )

“World” filter [ @ > 50 ]

All of the above

Answer

Correct Answer: “World” filter { c => c > 50 }
“World” filter { _ > 50 }
“World” filter ( _ > 50 )

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66.
Choose the correct description for the Scala 'Function Type'?

the trait FunctionN

there is no value - no object, no instance - with a Function type

a Function Type actually is a Method Value

None of the above

Answer

Correct Answer: the trait FunctionN

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67.
How to override type() java interface method in a scala class?

override def `type` = { ... }

override def type = { ... }

Both of the above

None of the above

Answer

Correct Answer: override def `type` = { ... }

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68.
Which of the following statement is false about Scala?

Nothing is a subtype of everything

Nil represents null similar in java

Unit represents type of method that doesn’t return a value

None signifies no result from the method

Answer

Correct Answer: Nil represents null similar in java

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69.
Choose the statement that best describes the line def this(c: String) = this(0, c); for the code fragment below. class ABC(a: Int, b: Int, c: String) { def this(a: Int, c: String) = this(a, 0, c) def this(c: String) = this(0, c); }

calls the primary constructor

calls previous auxiliary constructor which calls the primary constructor

calls the primary constructor

is an auxiliary constructor does not call the primary constructor

Answer

Correct Answer: calls previous auxiliary constructor which calls the primary constructor

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70.
A digital circuit is built from wires and function boxes. Wires carry signals which are transformed by function boxes. Signals will be represented by booleans: true for signal-on and false for signal-off. Which of the following are correct in context of the above statement?

An inverter, which negates its signal.

An and-gate, which sets its output to the conjunction of its input.

An or-gate, which sets its output to the disjunction of its input.

All of the above

Answer

Correct Answer: All of the above

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71.
Which of the following are the Keywords used in Scala? Check all that apply.

Var

Val

Yield

Sealed

Answer

Correct Answer: Var
Val
Sealed

Note: This question has more than 1 correct answers

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72.
The expression List.apply(1,2,3) is the same as?

List.instanceOf(1,2,3)

List(1,2,3)

new List(1,2,3)

None of the above

Answer

Correct Answer: List(1,2,3)

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73.
Choose the correct output of the following code fragment?
List("Who","is","longest?").foldLeft((0,""))((i,s) => if (i._1 < s.length) (s.length,s) else i )

(longest?)

(8)

(longest?,8)

(8,longest?)

Answer

Correct Answer: (8,longest?)

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74.
The primary tool Scala gives you to organize your programs is the class. A class is a blueprint for objects. Once you do a class, you can create objects from the class blueprint with the keyword new. Which of the following options is described by the above statements?

Classes and types

Objects and variables

Repeated parameters

Abstraction

Answer

Correct Answer: Classes and types

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75.
When writing the code of a Scala program, you create and interact with objects. To interact with a particular object, you can use a variable that refers to the object. You can do a variable with either a val or var, and assign an object to it. Which of the following option is described by the above statements?

Variables

Objects

Objects and variables

Objects, variables and array

Answer

Correct Answer: Objects and variables

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76.
Which of the following are scala identifiers? Check all that apply.

Mixed identifiers

Literal identifiers

Formatted identifiers

Alpha numeric identifiers

All of the above

Answer

Correct Answer: Mixed identifiers
Literal identifiers
Formatted identifiers

Note: This question has more than 1 correct answers

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77.
Choose the best reason why the code fails to compile, for the type hierarchy and expressions as following?
class A { } class B extends A {} class C { } class D extends C { } case class S[T <: A ](a: T*) {} val aa: S[A ] = S[( new B(), new A() ) val cc = S( new D() )

the variable cc needs to bee a collection like aa

In the expression "val cc = S( new D() )" The inferred type arguments [D] do not conform to apply method's type parameter bounds

the expression S[T <: A ](a: T*) should be `case class S[+T <: A ] to extend the sub classhierarchy

None of the above

Answer

Correct Answer: In the expression "val cc = S( new D() )" The inferred type arguments [D] do not conform to apply method's type parameter bounds

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78.
Choose the statement that is not correct about Scala's List?

List is an abstract class

List can be immutable

List is a trait

List inherits from Seq

Answer

Correct Answer: List is an abstract class

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79.
Which one of the following is a correct example of using toArray to convert to an array and toList to convert to a list?

scala> val buf = new Array[Int]() buf: scala.collection.mutable.toList.list[Int] = ArrayBuffer()

scala> val buf = new Array[Int]() buf: scala.collection.mutable.toList.ArrayBuffer[Int] = ArrayBuffer()

scala> buf.toArray res13: Array[Int] = Array(12, 15) scala> buf.toList res14: List[Int] = List(12, 15)

All of the above

Answer

Correct Answer: scala> buf.toArray res13: Array[Int] = Array(12, 15) scala> buf.toList res14: List[Int] = List(12, 15)

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80.
What will be the output for the code fragment?
List(1, 2, 1, 2, 1, 2, 1, 2, 1, 2).drop(1).sliding(1, 2).flatten.toList

List(2, 2, 2, 2)

List(1, 2)

List(1, 1, 2, 2)

List(2, 2, 2, 2, 2)

Answer

Correct Answer: List(2, 2, 2, 2, 2)

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81.
What will be the output for the code fragment below?
List(Set(1), Set(1,2,3), Set(1, 2)) diff List(Set(1,2,3))

List(Set(1, 2, 3), Set(1, 2))

List(Set(1, 2))

Set(1,2,3)

List( Set(1), Set(1, 2) )

Answer

Correct Answer: List( Set(1), Set(1, 2) )

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82.
Which of the following code snippets correctly represent Type inference on map method of Scala collections?

case class MapResult(input: Any, output: Map[_ <: Any, Any]) { override def toString = output.map(p => input + " " + p._1 + " " + p._2 ).mkString("\n") }

case class MapResult(input: Any, output: Map[_ <: Any, Any]) { override def toString = output.map(p: (Any, Any) => input + " " + p._1 + " " + p._2 ).mkString("\n") }

case class MapResult(input: Any, output: Map[_ <: Any, Any]) { override def toString = output.map{ case (k: Any, v: Any) => input + " " + k + " " + v }.mkString("\n") }

All of the above

Answer

Correct Answer: case class MapResult(input: Any, output: Map[_ <: Any, Any]) { override def toString = output.map{ case (k: Any, v: Any) => input + " " + k + " " + v }.mkString("\n") }

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83.
For the code below, Choose the correct statement?
List.tabulate(100)(a => a.toString)

Results in a mutable list

Results in an imutable list

Is equivalent to (1 to 100).map(_.toString)

Both 2 and 3.

Answer

Correct Answer: Results in an imutable list

Note: This Question is unanswered, help us to find answer for this one

84.
Create an array buffer just like an array, except that you do not need to specify a size. Which of the following implementation will adjust the allocated space automatically?

scala> val buf = new ArrayBuffer[Int]() buf: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()

scala> val buf = new Array[Int]() buf: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()

scala> val buf = new Array[Int]() buf: scala.collection.ArrayBuffer[Int] = ArrayBuffer()

All of the above

Answer

Correct Answer: scala> val buf = new ArrayBuffer[Int]() buf: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()

Note: This Question is unanswered, help us to find answer for this one

85.
Which one of the following code example of Scala collection type for filter is correct?

scala> List(1, "1") collect { | case x: Int => x | } res0: List[Int] = List(1)

scala> List(1, "1") map { | case x: Int => x | case y: String => y.toInt | }

scala> List(1, "1") filter { | case x: Int => true | case _ => false | }

All of the above

Answer

Correct Answer: scala> List(1, "1") collect { | case x: Int => x | } res0: List[Int] = List(1)

Note: This Question is unanswered, help us to find answer for this one

86.
Which one of the following statement is not correct for trait Iterator?

Iterator does not extend Traversable

Its only abstract operations are next and hasNext

Iterator extends Iterable

Iterator types are created by Iterable type

Answer

Correct Answer: Iterator extends Iterable

Note: This Question is unanswered, help us to find answer for this one

87.
Traits are used to define _ types by specifying the signature of the supported __?

class

object

methods

Answer

Correct Answer: object
methods

Note: This question has more than 1 correct answers

Note: This Question is unanswered, help us to find answer for this one

88.
For the code below, which of the following statement is True?
val data = "test" list = List("this", "is", "a", "test") what will be the effect of applying the expression below to the list list.filterNot(elm => elm == data)

As the list is immutable will have no effect

will remove all elements that are equal to "test"

will return all elements from the list except those which aren't equal to "test"

will return NONE

Answer

Correct Answer: will return all elements from the list except those which aren't equal to "test"

Note: This Question is unanswered, help us to find answer for this one

89.
Which of the following is false about Monads?

Set is a monad with unit(x) = Set(x)

List is a monad with unit(x) = List(x)

Option is a monad with unit(x) = Some(x)

Try is a monad with unit(x) = Try(x)

Answer

Correct Answer: Try is a monad with unit(x) = Try(x)

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90.
What is output of the following code?
def main(args: Array[String]) { val capitals = Map("France" -> "Paris", "Japan" -> "Tokyo") println("capitals.get( \"France\" ) : " + capitals.get( "France" )) println("capitals.get( \"India\" ) : " + capitals.get( "India" )) }

Some(Paris),None

RuntimeException

Paris, None

Paris

Answer

Correct Answer: Some(Paris),None

Note: This Question is unanswered, help us to find answer for this one

91.
Which of the following statement is false for traits?

Scala allows traits to be partially implemented

It is not possible to define default implementations for some methods

trait T {} is a valid trait definition

Similar to interfaces in Java, traits are used to define object types by specifying the

signature of the supported methods

Answer

Correct Answer: It is not possible to define default implementations for some methods

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92.
Which one is not reserved word in Scala?

yield

sealed

switch

val

Answer

Correct Answer: switch

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93.
Which of the following is Web Frameworks of Scala?

The List Framework

The Bowl framework

The Play framework

The Lift Framework

Answer

Correct Answer: The Play framework

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94.
Choose the option that best describes the difference between a var and val definition in Scala?

The object assigned to a val cannot be replaced

the object assigned to a var cannot be replaced

The object assigned to a val can be replaced

val is used to create an immutable object

Answer

Correct Answer: The object assigned to a val cannot be replaced

Note: This Question is unanswered, help us to find answer for this one

95.
In Scala everything is an Object, No ___?

case

primitives

output

end

Answer

Correct Answer: primitives

Note: This Question is unanswered, help us to find answer for this one

96.
Choose the best description for the variance expression as following?
A[B <: C]

A[B <: C] means that class A can take any class B that is a subclass of C.

A[B <: C] means that class B can take any class that is a subclass of C.

A[B <: C] means that class A can take any class B that is a subclass of C and propagate the subclass relationship.

A[B <: C] means that class A can take any class A that is a subclass of C.

Answer

Correct Answer: A[B <: C] means that class A can take any class B that is a subclass of C.

Note: This Question is unanswered, help us to find answer for this one

97.
Which of the following is false about Futures and Promises?

Once a Future object is given a value or an exception, it can never be overwritten

Futures are non-blocking while promises are blocking

A promise can be used to complete a future with an exception

Future and Promises revolve around ExecutionContexts, responsible for executing computations

Answer

Correct Answer: Futures are non-blocking while promises are blocking

Note: This Question is unanswered, help us to find answer for this one

98.
For the type heirachy defined below, Choose the most correct statement below for the output?
trait A{ def a = 1 } trait X extends A{ override def a = { println("X") super.a } } trait Y extends A{ override def a = { println("Y") super.a } } For the expression val xy = new AnyRef with X with Y xy.a

Prints NONE then Y

Prints X then NONE

Prints X then Y

Prints Y then X

Answer

Correct Answer: Prints Y then X

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99.
Given the type hierarchy defined below, Choose the most correct statement below?
trait A{ def a = 1 } trait X extends A{ override def a = { println("X") super.a } } trait Y extends A{ override def a = { println("Y") super.a } } For the expression val xy = new AnyRef with X with Y

The expression “with X with Y” is an example of the mixin syntax

The expression “with X with Y” is an example of multiple inheritance

The expression “with X with Y” is an explicit way of declaring parent priority

The expression “with X with Y” allows linearization of the inheritance hierarchy

Answer

Correct Answer: The expression “with X with Y” is an example of the mixin syntax

Note: This Question is unanswered, help us to find answer for this one

100.
For the code below abstract class A { type B <: C abstract class C { def superClassM(b: B): D } class EImpl extends C { def superClassM(b: B): D = { val e = func1(this, b) e } } def func1(b: B, b1: B): D = D(b, b1) case class D(a: B, b: B) } The code produces the following compile error found : EImpl.this.type (with underlying type A.this.EImpl) required: A.this.B val e = func1(this, b) ^
Choose the expression that allows the code to compile

trait C { def superClassM(b: B): D }

class C { def superClassM(b: B): D }

type B = C

type B >: C

Answer

Correct Answer: type B = C

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101.
For the code below, Choose the correct statement which explains the error?
abstract class A { type B <: C abstract class C { def superClassM(b: B): D } class EImpl extends C { def superClassM(b: B): D = { val e = func1(this, b) e } } def func1(b: B, b1: B): D = D(b, b1) case class D(a: B, b: B) } When complied produces the following error found : EImpl.this.type (with underlying type A.this.EImpl) required: A.this.B val e = func1(this, b) ^

func1 is an abstract method and must be defined in a trait

class EImpl is abstract

B is an abstract type

C should be defined as a trait

Answer

Correct Answer: B is an abstract type

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102.
Choose the best description that describes the Scala classes 'scala.AnyRef ' and 'scala.AnyVal'?

Value classes extend scala.AnyVal and are predefined types, reference classes extend scala.AnyRef and are user defined

Value classes extend scala.AnyVal and are predefined types, while reference classes extend scala.AnyRef and are used for primitive type objects

Value classes extend scala.AnyVal and are predefined types, while all other classes are reference classes that extend scala.AnyRef

Value classes extend scala.AnyVal and are predefined types, while other classes in the Scala language are reference classes that extend scala.AnyRef except user defined class which extend scala.ScalaObject class

Answer

Correct Answer: Value classes extend scala.AnyVal and are predefined types, while all other classes are reference classes that extend scala.AnyRef

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103.
What will the result using the following code?
List(None, Some(1), None, Some(2)).flatMap(x => x)

List(None,1,None,2)

List(1,2)

List(None, Some(1), None, Some(2))

Compile Error

Answer

Correct Answer: List(1,2)

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104.
How can you make a List[String] from a given val x = List[List[String]]?

x.flatMap

x.map

x.collect

x.flatten

Answer

Correct Answer: x.flatten

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105.
Which of the following is not valid using List?

val list :List[Int] = List()

val list = 1 :: List("abc",'a',1,List(1,2))

val list :List[Int]= List(1,2,3)

val list :List[Int] = List() :: 1

Answer

Correct Answer: val list :List[Int] = List() :: 1

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106.
What is the output of the following code?
def main(args: Array[String]) { printMe(c = 4, b = 5, a = 7); def printMe( a:Int, b:Int, c:Int) = { println( a,b,c ); } }

4,5,7

Compile error

7,5,4

5,7,4

Answer

Correct Answer: 7,5,4

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107.
The map method on List (and Seq), transforms each element of a collection based on a function. For example, if we have a List[String] and want to convert it to all lowercase?

scala> Map("A", "Cat").list(s => s.LowerCase)

scala> List("A", "Cat").map(s => s.toLowerCase)

scala> List("A", "Cat").map(s => s.LowerCase)

All of the above

Answer

Correct Answer: scala> List("A", "Cat").map(s => s.toLowerCase)

Note: This Question is unanswered, help us to find answer for this one

108.
Choose the statement that is not correct for Scala's mutable.Map?

mutable.Map is an Iterable of Tuple2

mutable.Map has an update method for setting keys

mutable.Map has a withDefaultValue method that returns a default for keys

mutable.Map has a withDefaultValue method that returns a default for undefined keys

Answer

Correct Answer: mutable.Map has a withDefaultValue method that returns a default for undefined keys

Note: This Question is unanswered, help us to find answer for this one

109.
Choose the correct output using the code fragment below?
listOfInts.sliding(2).toList

List(1, 2), List(2, 3)

List(1), List(2), List(3)

List(List(1), List(2), List(3))

List( List(1, 2), List(2, 3) )

Answer

Correct Answer: List( List(1, 2), List(2, 3) )

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110.
How to groupBy using multiple columns in Scala collections?

records.groupBy(record => (record.column1, record.column2, record.column3))

records.setgroup(record => (record.column1, record.column2, record.column3))

records.groupSet(record => (record.column1, record.column2, record.column3))

All of the above

Answer

Correct Answer: records.groupBy(record => (record.column1, record.column2, record.column3))

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111.
What is the output of following code?
def main(args: Array[String]) { val x = {print("x");1} lazy val y = {print("y");2} def z = {print("z"); 3} z+y+x+z+y+x }

zyxzyx

xyzz

zyzz

xzyz

Answer

Correct Answer: xzyz

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112.
For the code below, Choose the correct statement that describes an issue with the code?
val L = List[String]() for (a <- 1 to 100) { L :+ a.toString }

L is a mutable list

“L:+ a.toString” is returning a new list each time

“L:+ a.toString” yields a comprehension

for (a <- 1 to 100) { L :+ a.toString } is equivalent to (1 to 100).map(_.toString)

Answer

Correct Answer: “L:+ a.toString” is returning a new list each time

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113.
What is the output of given code below?
def addInt( a:Int = 5, b:Int = 7 ) : Int = a + b print(addInt(3,7),addInt(3),addInt(),addInt(b=5))

10,10,12,10

Compile Error

10, 10, 12, 12

12,12,12,12

Answer

Correct Answer: 10,10,12,10

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114.
What is the output of the following code?
object MatchTest { def matchTest(x: Any): Any = x match { case 1 => "one" case "two" => 2 case y: Int => "scala.Int" } def main(args: Array[String]) { println(matchTest(2)) } }

Compile error

Runtime error

scala.Int

Answer

Correct Answer: scala.Int

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115.
Choose the statement that is not correct using the code below?
(1 to 10).par map println

If you add par you get a parallel collection and operations on it will always be processed in parallel.

If you add par you get a parallel collection and operations on it will always be processed in parallel only if more than one system thread is avaiable

Splits your list for processing over several threads

As par is acting on a range it copys the elements into a ParRange

Answer

Correct Answer: If you add par you get a parallel collection and operations on it will always be processed in parallel only if more than one system thread is avaiable

Note: This Question is unanswered, help us to find answer for this one

116.
For the code below, Choose the correct statement which shows the output?
var l1 = scala.collection.mutable.MutableList[String]() val l2 = List[String]() for (a <- 1 to 100) { l1 += a.toString } println(l1 .size); for (a <- 1 to 100) { l2 :+ a.toString } println(l2 .size);

100 the 100

0 then 100

100 then 0

0 then 0

Answer

Correct Answer: 100 then 0

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117.
Choose the following statement that is not correct for parallel collections?

You can replace a non-parallel collection with a parallel one

Any collection can be converted into a parallel one by calling the method par on it

Calling toSeq on a parallel collection will return a serial collection.

The parallel collections hierarchy has the same names for traits, but preceded with Par

Answer

Correct Answer: Calling toSeq on a parallel collection will return a serial collection.

Note: This Question is unanswered, help us to find answer for this one

118.
If Seq is a trait then why is var x = Seq(1, 2, 3) legal?

Seq is an implementation

Seq is not a trait its an object

Seq is not a trait its a collection

You are calling the apply method on the object

Answer

Correct Answer: You are calling the apply method on the object

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119.
You can convert any collection. to an array or a list. Such conversion requires copying all of the elements of the collection,and thusis slow for large collections. Sometimes you need to do it, though, due to an existing API. Further, many collections only have a few elements anyway, in which case there is only a small speed penalty?

Conversion

Lists

Arraybuffers

Array

Answer

Correct Answer: Conversion

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120.
Scala provides __ versions of all of its collection types. These versions cannot be changed after they are initialized. You should use them whenever you know a collection should not be changed, so that you do not accidentally change it later?

immutable

initializing

conversion

lists

Answer

Correct Answer: immutable

Note: This Question is unanswered, help us to find answer for this one

121.
For the code below, choose the correct statement which describes the code?
object A extends B with C { def f(x: Any): Any = ??? }

Declares an anonymous class that extends both B and C

Defines class B , and create all of the methods in object B as static methods on class B

If a class named C is explicitly defined then A will be a companion object to C

Declares a companion class A

Answer

Correct Answer: Declares an anonymous class that extends both B and C

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122.
What is the best way to “clone” a case class?

Specifcally call all fields and use the constructor

Specifcally call all fields and use the apply function

Use the copy method

Use the comapnion object

Answer

Correct Answer: Use the copy method

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123.
String interpolation allows users to _____ variable references directly in processed string literals?

Embed

Global

Constant

Static

Answer

Correct Answer: Embed

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124.
Using the following code fragment, Choose the correct statement which solves the error?
class A(n: Int) { var value = n } class B(n: Int) { val value = new A(n) } object Test { class A(n: Int) { var value = n } class B(n: Int) { val value = new A(n) } object Main extends App { val x = new B(5) x.value = 6 } When complied produces the following error Main.scala:7: error: reassignment to val x.value = 6 ^

x.value.value = 6

x.value = A(6)

x.value = new A(6)

x.value.value = new A(6)

Answer

Correct Answer: x.value.value = 6

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125.
Choose the statement that is not correct for trait Traversable?

its only abstract operation is def foreach[U](f: Elem => U)

Traversible objects can be finite or infinite

All collections extend Traversible

Traversible objects can not be infinite

Answer

Correct Answer: Traversible objects can not be infinite

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126.
Read the following code and tell when do Scala functions execute?

scala> def showname() = println("this is a string") showname: ()Unit scala> showname this is a string scala> showname _ res1: () => Unit =

scala> res1 res2: () => Unit = scala> res1() this is a string scala> def showname(s: String) = println("this is a string") showname: (s: String)Unit scala>

showname :9: error: missing arguments for method showname; follow this method with `_' if you want to treat it as a partially applied function showname

All of the above

Answer

Correct Answer: All of the above

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127.
For the code fragment below, Choose the expression that shows the correct output?
object Main extends App { val adder = new Adder(2) System.out.println(adder.apply(4)) } class Adder(x: Int) { var y = 5 def apply(y: Int) = x + y }

Compile error

None

Answer

Correct Answer: 6

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128.
Choose the statement that best describe's the Scala 'apply' function?

When you give parameters directly to an object then you you pass these parameters to the apply function of that object

The apply function is explicitly defined in case class objects

The apply function is an Auxiliary constructor

When you construct an object with parameters then you you pass parameters implicitly to the apply function of that object

Answer

Correct Answer: When you give parameters directly to an object then you you pass these parameters to the apply function of that object

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129.
Which of the following is false for Scala?

Scala is a pure object oriented language

Scala supports generic classes

Scala supports higher order functions

Scala is pure functional

Answer

Correct Answer: Scala is pure functional

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130.
For the code fragment below choose the correct statement?
val aa = bb filter (x => x % 2 == 0)

aa will be a new collection, while bb will still be the same as before

aa will be a new collection, while bb will create a new copy of bb for the filter operation

aa will be a new collection, while filter operation will create a new mutable copy of bb

aa will be a new mutable collection, while bb will still be the same as before

Answer

Correct Answer: aa will be a new collection, while bb will still be the same as before

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131.
For the code fragment below
object Main extends App { def mySum[T <: Number](as: T*): Double = as.foldLeft(0d)(_ + _.doubleValue) implicit def intToInteger(n: Int): Integer = new Integer(n.toInt) var r = mySum(2, 3) }
When complied produces the following error, Choose the correct statement which solves the error when you remove the line implicit def intToInteger(n: Int): Integer = new Integer(n.toInt) Main.scala:4: error: inferred type arguments [Int] do not conform to method mySum's type parameter bounds [T <: Number] var r = mySum(2, 3) ^

def mySum[T >: Number](as: T*): Double = as.foldLeft(0d)(_ + _.doubleValue)

def mySum[T <% Number](as: T*): Double = as.foldLeft(0d)(_ + _.doubleValue)

def mySum[T <: Double](as: T*): Double = as.foldLeft(0d)(_ + _.doubleValue)

def mySum[T >: Double](as: T*): Double = as.foldLeft(0d)(_ + _.doubleValue)

Answer

Correct Answer: def mySum[T <% Number](as: T*): Double = as.foldLeft(0d)(_ + _.doubleValue)

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132.
For the code fragment below, Choose the expression that shows the correct output?
object Main extends App { val adder = new Adder(2) System.out.println(adder.apply(4)) var a = new Adder(4) System.out.println(a.applyObj()) } class Adder(x: Int) { var y = 5 def apply(y: Int) = x + y def applyObj() = x + y }

9 then 6

Compile error

6 then None

6 then 9

Answer

Correct Answer: 6 then 9

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133.
Which of the following is true for Objects, Traits and Classes?

To create a program you should use main method in class

You can have multiple instances of a class

An object has exactly one instance, you can not call new MyObject

object A extends B with C. In this definition A is object B is class and C is trait

Answer

Correct Answer: To create a program you should use main method in class

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134.
Which of the following code statement is correct, Using scala object inside java?

scala.util.List res = scala.collection.JavaConverters$.MODULE$.seqAsJavaListsConverter(variableName).asJava();

scala.util.List res = scala.collection.JavaConverters$.MODULE$.seqAsJavaListConverter(variableName).asJava();

java.util.List res = scala.collection.JavaConverters$.MODULE$.seqAsJavaListConverter(variableName).asJava();

Seq variableName = ScalaClass.MethodInTheScalaClass();

Answer

Correct Answer: java.util.List res = scala.collection.JavaConverters$.MODULE$.seqAsJavaListConverter(variableName).asJava();

Note: This Question is unanswered, help us to find answer for this one

135.
Choose the correct description for both expressions, for the two expressions as following? expression 1 def m1(i:Int)=i+2 expression 2 (i:Int)=>i+2

expression 1 is a function

expression 2 is a method

expression 1 is a method

expression 2 fails to compile

Answer

Correct Answer: expression 1 is a method

Note: This Question is unanswered, help us to find answer for this one

136.
How do you provide overloaded constructors in Scala?

Use the “this” keyword like def this(...

Overloading the apply function

You can’t overload constructors, but you can do this with functions

Parameters with default values must come before the ones with no default values

Answer

Correct Answer: Use the “this” keyword like def this(...

Note: This Question is unanswered, help us to find answer for this one

137.
For the code below, Choose the best statement to describe this error?
class A(n: Int) { var value = n } class B(n: Int) { val value = new A(n) } object Test { def main(args: Array[String]) { val x = new B(5) x = new B(6) } } Main.scala:7: error: reassignment to val x = new B(6) ^

Objects created with var are immutable

I can not replace the object created on the line above B(6) with this new one.

I need to replace x = new B(6) with x = B(6)

I need to replace x = new B(6) with x = B.apply(6)

Answer

Correct Answer: I can not replace the object created on the line above B(6) with this new one.

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138.
Which one of the following about functional combinators is false?

foreach evaluates a function over each element in the list but returns nothing

map evaluates a function over each element in the list, returning a list with the same number of elements

find returns the all elements of a collection that matches a predicate function

zip aggregates the contents of two lists into a single list of pairs

Answer

Correct Answer: find returns the all elements of a collection that matches a predicate function

Note: This Question is unanswered, help us to find answer for this one

139.
Using the code fragment below, Choose the correct statement which explains the error?
object Main extends App { def mySum[T <: Number](as: T*): Double = as.foldLeft(0d)(_ + _.doubleValue) implicit def intToInteger(n: Int): Integer = new Integer(n.toInt) var r = mySum(2, 3) } When complied produces the following error Main.scala:4: error: inferred type arguments [Int] do not conform to method mySum's type parameter bounds [T <: Number] var r = mySum(2, 3) ^

Class Int belongs to the value classes whose instances are not represented as objects

[T <: Number] type bounds means that T must be a subtype of Number

There is no implicit conversion from instances of Int to instances of Double

You importing scala.math.BigInt._?

Answer

Correct Answer: [T <: Number] type bounds means that T must be a subtype of Number

Note: This Question is unanswered, help us to find answer for this one

140.
Which of the following statement is false about the functions in Scala?

It is possible to define def add(x:Int, y:Int) = x + y as def add(x:Int) (y:Int) = x + y c ) Following code gives compile error

Functions that take other functions as parameters, or whose result is a function are higher order functions

var userDir = () => { System.getProperty("user.dir") } println( userDir )

it is possible to nest function definitions. like def test = { def nestedTest = { println("nestedTest") } nestedTest }

Answer

Correct Answer: It is possible to define def add(x:Int, y:Int) = x + y as def add(x:Int) (y:Int) = x + y c ) Following code gives compile error

Note: This Question is unanswered, help us to find answer for this one

141. True or False? Scala compiler automatically infers function parameter types.

True

False

Answer

Correct Answer: False

Note: This Question is unanswered, help us to find answer for this one

142. def f(): Int = try { return 1 } finally { return 2 } Calling f() results in

Exception

Answer

Correct Answer: 2

Note: This Question is unanswered, help us to find answer for this one

143. A function which associates a value to a (variable) name is known as a(n):

Operation

Class

Method

Environment

Answer

Correct Answer: Environment

Note: This Question is unanswered, help us to find answer for this one

144. What is the runtime class of Unit?

type[Unit]

Class[Unit]

Unit

Nothing

Answer

Correct Answer: Class[Unit]

Note: This Question is unanswered, help us to find answer for this one

145. What is the Scala development environment designed for use in schools?

Kojo

Typesafe

Venner

FODEM

Answer

Correct Answer: Kojo

Note: This Question is unanswered, help us to find answer for this one

146. "Option" is:

an abstract class

a concrete class

a case class

an interface

a trait

Answer

Correct Answer: an abstract class

Note: This Question is unanswered, help us to find answer for this one

147. Which of the following is not one of the ways to increment the value of a variable i of type Int by 1.

i = i + 1

i++

ii+

i += 1

Answer

Correct Answer: i++

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148. def g(): Int = try { 1 } finally { 2 } Calling g() results in

Exception

Answer

Correct Answer: 1

Note: This Question is unanswered, help us to find answer for this one

149. Which of the following descriptions of case classes is NOT correct:

Case classes come with apply and unapply methods.

Case classes have default serializers

Case classes are always immutable.

Case classes can be used in matchers.

Answer

Correct Answer: Case classes are always immutable.

Note: This Question is unanswered, help us to find answer for this one

150. Which statement about the Option[+A] class is false?

Option[+A] is abstract.

scala.Nothing is derived from Option[+A]

Option[+A] is meant to replace the usage of null.

None is derived from Option[+A]

Answer

Correct Answer: scala.Nothing is derived from Option[+A]

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151. Which of these are NOT ways in which case classes differ from standard classes?

Default deﬁnitions for the methods "equals" and "hashCode" are not provided

A default deﬁnition for method "toString" is provided, and prints the value in a source form

The "new" keyword is not mandatory to create instances of case classes

Getter functions are automatically deﬁned for the constructor parameters

Answer

Correct Answer: Default deﬁnitions for the methods "equals" and "hashCode" are not provided

Note: This Question is unanswered, help us to find answer for this one

152. Which predicate tests whether x is object identical to y?

x eq y

x.object == y.object

x == y

x = y

Answer

Correct Answer: x eq y

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153. Are parenthesis `(` and curly braces `{` interchangeable?

Only if the method expects a single parameter.

Not unless the function supports covariant type parameters.

Not unless the function supports contravariant type parameters.

Only if the method expects a partial function.

Answer

Correct Answer: Only if the method expects a single parameter.

Note: This Question is unanswered, help us to find answer for this one

154. What is a lazy var?

A variable that is only evaluated once

`lazy var` is not supported by Scala

An immutable variable

A variable that once evaluated can only be referenced by the creating scope.

Answer

Correct Answer: `lazy var` is not supported by Scala

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155. What would be returned by the following function: def foo(l:List[Int]) = { var x=l.head; l.collect{ case a:Int if a>x => x=a; a }; x } When passed: List(2,4,6,8,6,3,1)

Nothing, there's no return value.

Answer

Correct Answer: 8

Note: This Question is unanswered, help us to find answer for this one

156. `() => Unit` is best described as

`() => Unit` is not valid Scala

A pure function

A function literal

A procedure type definition

Answer

Correct Answer: A procedure type definition

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157. What will the following function return: def foo(o:Any) = { o match { case Option(x) => "hi!" case anything => anything } } When passed a 'None' object?

it will return the None because it matches on 'anything'

It will return "hi!" because a 'None' is a type of 'Option'

It won't compile

It will return 'anything'

Answer

Correct Answer: It won't compile

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158. Is it possible in Scala to declare a variable of type `Int` with a value of `null`?

Yes

Answer

Correct Answer: No

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159. What is the data type of myVariable in the following: val myVariable = if (true) "Hello"

String

Any

Unit

Answer

Correct Answer: Any

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160. True or False? In the Interpreter, you can define a new val with a name that was already used before.

False

True

Answer

Correct Answer: True

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161. Which statement about List is false?

A List is a finite immutable sequence

A List is optimal for last-in-first-out (LIFO), stack-like access patterns

List is a proxy for java.util.ArrayList

A List is covariant

Answer

Correct Answer: List is a proxy for java.util.ArrayList

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162. How would you define the method: def +(a:Int):Int in a Java interface that will be overriden or used in Scala code?

public int %plus(int a)

You can't define a scala operator using Java source code.

public int #plus(int a)

private int $plus(int a)

public int $plus(int a)

Answer

Correct Answer: public int $plus(int a)

Note: This Question is unanswered, help us to find answer for this one

163. Which statement about pattern matching is true?

The order of the pattern match is irrelevant

The case set must be exhaustive

Pattern matching does not work with case classes

Patterns do not work with structural types

Answer

Correct Answer: The case set must be exhaustive

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164. True or False? Scala provides static members (members or fields).

True

False

Answer

Correct Answer: False

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165. When no super-class is speciﬁed, ______ is implicitly used.

scala.AnyRef

You must always specify super-class

scala.importRef

scalac use.ref

Answer

Correct Answer: scala.AnyRef

Note: This Question is unanswered, help us to find answer for this one

166. What is the name of the Scala compiler?

"scalacom"

"cScala"

"scala.comp"

"scalac"

Answer

Correct Answer: "scalac"

Note: This Question is unanswered, help us to find answer for this one

167. Everything, including numbers and functions, are _______ in Scala.

Objects

Methods

Booleans

Operations

Answer

Correct Answer: Objects

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168. What is a class with a single instance?

A mono object

A single argument

A singleton object

A static object

Answer

Correct Answer: A singleton object

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169. Which of the following best describes Scala?

A functional language

All of these choices describe Scala

An object oriented language

A language that runs on the VM

Answer

Correct Answer: All of these choices describe Scala

Note: This Question is unanswered, help us to find answer for this one

170. Scala's "Unit" roughly corresponds to which Java type?

"void"

"bool"

"null"

"get"

Answer

Correct Answer: "void"

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171. When a class inherits from a trait, it inherits all the code contained in the trait and implements the trait's:

Interface

Framework

Arguments

Platform

Answer

Correct Answer: Interface

Note: This Question is unanswered, help us to find answer for this one

172. True or False? Like pre 1.5 Java, Scala suffers from lack of genericity.

True

False

Answer

Correct Answer: False

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173. Does Scala support the return keyword?

Yes, but only for traits.

Yes, but it is not idiomatic Scala and therefor discouraged.

Yes, all methods and functions must have at least one return statement.

Answer

Correct Answer: Yes, but it is not idiomatic Scala and therefor discouraged.

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174. True or False? Multiple classes can be imported from the same package by enclosing them in curly braces {}.

True

False

Answer

Correct Answer: True

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175. Scala is:

A dynamic language that can be used to program in object-oriented style efficiently

An advanced Object-Oriented Language much better than Java that runs on the JVM

An advanced Java language implemented by Martin Odersky

An object-functional language that supports functional programming constructs

A pure functional programming language

Answer

Correct Answer: An object-functional language that supports functional programming constructs

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176. What would be the result of: Option[String]("hi") match { case None=> "hello!" }

A MatchError would be thrown.

Nothing would happen because "hi" is not of type "None"

The statement would return "hello!"

A NullPointerException would be thrown.

Answer

Correct Answer: A MatchError would be thrown.

Note: This Question is unanswered, help us to find answer for this one

177. What is an expression following the "if" keyword?

A guard

A tree

An array

A wild-card

Answer

Correct Answer: A guard

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178. True or False? Methods taking one argument can be used with infix syntax?

False

True

Answer

Correct Answer: True

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179. Which statement best describes an Iterator

An iterator is a collection type

Scala does not support Iterators

An Iterator is a stream of incoming items where advancing to the next item consumes the current item

An Iterator trait is mixed into all collection types

Answer

Correct Answer: An Iterator is a stream of incoming items where advancing to the next item consumes the current item

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180. What is a higher-order function?

Scala does not support higher-order functions

Higher-order functions are parameterless functions that return themselves

Higher-order functions are functions that take other functions as parameters.

Higher-order functions are functions that return functions

Answer

Correct Answer: Higher-order functions are functions that take other functions as parameters.

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181. Explain how "abc".length returns 3

All string literals are an instance of scala.collection.immutable.StringOps

A subclass of java.lang.String is generated at runtime, adding the `length` method to its signature.

An implicit conversion converts the java.lang.String into a scala.collection.immutable.StringOps, which supports a length method.

All string literals can be processed by Scala String interpreter.

Answer

Correct Answer: An implicit conversion converts the java.lang.String into a scala.collection.immutable.StringOps, which supports a length method.

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182. What is the value of the following expression? { val a = List(1,2,3) val b = List(4,5,6) (a,b).zipped.map(_+_) }

(List(1,2,3),List(4,5,6))

List(1,2,3,4,5,6)

List(5,7,9)

List((1,4),(2,5),(3,6))

Answer

Correct Answer: List(5,7,9)

Note: This Question is unanswered, help us to find answer for this one

183. Which of the following is a pattern matching any value, without giving it a name, represented by " _ "?

A simple class

A placeholder

A guard

A function

Answer

Correct Answer: A placeholder

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184. True or False? Scala compiler will never require you to specify the result type of a function.

True

False

Answer

Correct Answer: False

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185. The following code will > var x=100; var y=200; x->y

automatically create a List[T] with x and y as members with T of 'Int' type

a Tuple with Arity 2

assign 100 to variable y

treat x and y as same references in the further code

produce a compile error

Answer

Correct Answer: a Tuple with Arity 2

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186. In Scala, type parameters and abstract types may be constrained by a _____.

Type safe

Type call

Type bound

Type function

Answer

Correct Answer: Type bound

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187. Scala supports which types of polymorphism?

Subtype, ad-hoc and parametric polymorphism

Subtype and parametric

None of these

Parametric

Ad-hoc and parametric

Answer

Correct Answer: Subtype, ad-hoc and parametric polymorphism

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188. Witch one of the following operators is use for sequencing Parsers

Answer

Correct Answer: ~

Note: This Question is unanswered, help us to find answer for this one

189. It is possible to override methods inherited from a _____ in Scala.

Base-class

Super-script

Super-class

Function-class

Answer

Correct Answer: Super-class

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190. What is the result type of the following expression? List(1, 2, true, false)

List[Any]

List[Int]

List[AnyRef]

List[Boolean]

List[AnyVal]

Answer

Correct Answer: List[AnyVal]

Note: This Question is unanswered, help us to find answer for this one

191. Which statement best describes a partial function?

When applying the function, you do not pass in arguments for all of the parameters defined by the function, but only for some of them, leaving the remaining ones blank

A function that support currying

A partially defined function.

An internal function type that is used by the scala.collection.immutable package.

Answer

Correct Answer: When applying the function, you do not pass in arguments for all of the parameters defined by the function, but only for some of them, leaving the remaining ones blank

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192. In the expression: List(1,2,3) reduceLeft ( (a,b) => a+b ) `b` refers to:

The "fold" operation

The current sum while iterating through the list

The next element in the list

The return value for the expression

Answer

Correct Answer: The next element in the list

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193. Which statement about case classes is false?

Case classes as sealed and therefor cannot be extended

You can construct instances of these classes without using the new keyword

The toString method is automatically redefined

The equals method is automatically redefined

Answer

Correct Answer: Case classes as sealed and therefor cannot be extended

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194. What is the defaut parameter call semantics?

By Inference

By Value

By Name

By Reference

Answer

Correct Answer: By Value

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195. Classes in Scala, in contrast to Java, can have ______.

Functions

Parameters

Concepts

Constructs

Answer

Correct Answer: Parameters

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196. What is the tool "schema2src" used for?

Data-binding

Unifying types

Sealing classes

Currying

Answer

Correct Answer: Data-binding

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197. `Nil` is generally the same as:

Nothing

null

List()

None

Answer

Correct Answer: List()

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198. Does Scala support tail-call recursion?

Yes, the JVM runtime supports tail-call optimization.

Partly at the compiler level. The compiler will try and unwind the recursive call into a loop.

Partly, because the stack is infinite in Scala.

Answer

Correct Answer: Partly at the compiler level. The compiler will try and unwind the recursive call into a loop.

Note: This Question is unanswered, help us to find answer for this one

199. A valid description of a covariant type parameter would be:

A type parameter which is fixed when the class is subtyped.

A type parameter which is allowed to vary up for super types.

A type parameter which is fixed for super types.

A type parameter which is allowed to vary down as the class is subtyped.

Answer

Correct Answer: A type parameter which is allowed to vary down as the class is subtyped.

Note: This Question is unanswered, help us to find answer for this one

200. Describe class AnyRef

AnyRef is the root Object in Scala

There is no such class

AnyRef is derived from AnyVal

All types except the value types descend from AnyRef

Answer

Correct Answer: All types except the value types descend from AnyRef

Note: This Question is unanswered, help us to find answer for this one

201. In the expression: List(1,2,3).foldLeft(x){case (a,b) => a+b} `x` is:

A default value, only used if the list is empty

A list, to which the results are appended.

The "accumulator," which is the initial value for `b`

The "accumulator," which is the initial value for `a`

Answer

Correct Answer: The "accumulator," which is the initial value for `a`

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202. How would you get a List that was the result of appending `5:Int` to a `List(1,2,3)`. The order of the elements in the resulting List is irrelevant.

List(1,2,3) :: List(5)

List(1,2,3) + 5

List(1,2,3) :+ 5

List(1,2,3) ::= 5

List(1,2,3) :: 5

Answer

Correct Answer: List(1,2,3) :+ 5

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203. If you are defining scala classes in a 'package examplepackage', and want to ensure that a function 'foo' is only accessible by classes defined in the same package, how would you declare that function?

private[examplepackage] def foo = {...}

package[examplepackage] def foo={...}

def foo={...} //default access

package def foo={...}//package private

[examplepackage]private def foo={...}

Answer

Correct Answer: private[examplepackage] def foo = {...}

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204. When importing all the names of a package or class, which character do you use instead of " * "?

"&"

"@"

"$"

"_"

Answer

Correct Answer: "_"

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Scala MCQs | Topic-wise

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Basic Scala MCQ

1. What is the value of z after executing this code? val y = List('a','b') val z = y::List('c')

2. Q2. What value does this code return? val m1 = Map("a"->1,"b"->2,"c"->3) m1("a")

3. What value does this code return? x= List(1,2,4); x(1)?

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

5. What is a free variable?

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

7. In scala what is precondition?

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

9. What is denotes the intersection between two sets?

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

11. Why would you make a field private?

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

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

14. What are defined inside a class definition?

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

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

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

18. 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?

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

20. What is an advantage of an immutable object?

21. What is the code below equivalent to? myClass.foreach(println _)

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

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

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

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

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

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

28. Which statement returns a success or a failure indicator when you execute this code? val MyFuture = Future {runBackgroundFunction() }

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

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

31. What do you call objects with immutable state?

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

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

34. What is the data type of y after this code is executed? val y = (math floor 3.1415 * 2)

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

36. What term is used to specify a precondition?

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

38. Which is a subclass of all classes?

39. What type of object does this code create? val x = (1234, "Active")

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

41. What type of number is 1234.e5?

42. After defining a function in the interpreter, Scala returns the following. What does the () indicate? myfnc: ()Unit

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

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

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

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

47. Despite using the same code, the different browser and database modules created really are separate modules. This means that each module has its own contents, including any nested classes. Which of the following options is described by the above statements?

48. Regex class is available in the ........................ package.

49. Which of the following is false about Case Class?

50. Choose the correct statement that describes an 'abstract sealed' class?

51. Scala is ................ with Java. The two languages are interoperable with each other.

52. Choose the correct statements that describe a Scala Case class?

53. Which of the following describe using Scala class that is defined in a package object from Java?

54. Often a module is too large to fit comfortably into a single file. When that happens, you can use traits to split a module into separate files. Which of the following is described by the above statement?

55. Which of the following is not valid in Scala?

56. When Extractor object is using the match statement, the unapply method will be __ executed.

57. Which one of the following options is equivalent to the code below? for { x <- 1 to 10 y <- 1 to 10 } yield (x,y)

58. Which of the following are types of function in Scala?

59. Which of the following statement is about Scala anonymous function?

60. How to return a value from a scala function?

61. Which of the following one is Accessing scala object fields from java?

62. Which of the following are functional trio in Scala?

63. This trait consists of which of the following methods?

64. If you want to compare two objects to see if they are equal, you should usually use either ==, or its inverse !=. Which of the following code is true?

65. Which of the following are function Literal's in Scala?

66. Choose the correct description for the Scala 'Function Type'?

67. How to override type() java interface method in a scala class?

68. Which of the following statement is false about Scala?

69. Choose the statement that best describes the line def this(c: String) = this(0, c); for the code fragment below. class ABC(a: Int, b: Int, c: String) { def this(a: Int, c: String) = this(a, 0, c) def this(c: String) = this(0, c); }

70. A digital circuit is built from wires and function boxes. Wires carry signals which are transformed by function boxes. Signals will be represented by booleans: true for signal-on and false for signal-off. Which of the following are correct in context of the above statement?

71. Which of the following are the Keywords used in Scala? Check all that apply.

72. The expression List.apply(1,2,3) is the same as?

73. Choose the correct output of the following code fragment? List("Who","is","longest?").foldLeft((0,""))((i,s) => if (i._1 < s.length) (s.length,s) else i )

74. The primary tool Scala gives you to organize your programs is the class. A class is a blueprint for objects. Once you do a class, you can create objects from the class blueprint with the keyword new. Which of the following options is described by the above statements?

76. Which of the following are scala identifiers? Check all that apply.

77. Choose the best reason why the code fails to compile, for the type hierarchy and expressions as following? class A { } class B extends A {} class C { } class D extends C { } case class S[T <: A ](a: T*) {} val aa: S[A ] = S[( new B(), new A() ) val cc = S( new D() )

78. Choose the statement that is not correct about Scala's List?

79. Which one of the following is a correct example of using toArray to convert to an array and toList to convert to a list?

80. What will be the output for the code fragment? List(1, 2, 1, 2, 1, 2, 1, 2, 1, 2).drop(1).sliding(1, 2).flatten.toList

47.
Despite using the same code, the different browser and database modules created really are separate modules. This means that each module has its own contents, including any nested classes. Which of the following options is described by the above statements?

48.
Regex class is available in the ........................ package.

49.
Which of the following is false about Case Class?

50.
Choose the correct statement that describes an 'abstract sealed' class?

51.
Scala is ................ with Java. The two languages are interoperable with each other.

52.
Choose the correct statements that describe a Scala Case class?

53.
Which of the following describe using Scala class that is defined in a package object from Java?

54.
Often a module is too large to fit comfortably into a single file. When that happens, you can use traits to split a module into separate files. Which of the following is described by the above statement?

55.
Which of the following is not valid in Scala?

56.
When Extractor object is using the match statement, the unapply method will be __ executed.

57.
Which one of the following options is equivalent to the code below? for { x <- 1 to 10 y <- 1 to 10 } yield (x,y)

58.
Which of the following are types of function in Scala?

59.
Which of the following statement is about Scala anonymous function?

60.
How to return a value from a scala function?

61.
Which of the following one is Accessing scala object fields from java?

62.
Which of the following are functional trio in Scala?

63.
This trait consists of which of the following methods?

64.
If you want to compare two objects to see if they are equal, you should usually use either ==, or its inverse !=. Which of the following code is true?

65.
Which of the following are function Literal's in Scala?

66.
Choose the correct description for the Scala 'Function Type'?

67.
How to override type() java interface method in a scala class?

68.
Which of the following statement is false about Scala?

69.
Choose the statement that best describes the line def this(c: String) = this(0, c); for the code fragment below. class ABC(a: Int, b: Int, c: String) { def this(a: Int, c: String) = this(a, 0, c) def this(c: String) = this(0, c); }

70.
A digital circuit is built from wires and function boxes. Wires carry signals which are transformed by function boxes. Signals will be represented by booleans: true for signal-on and false for signal-off. Which of the following are correct in context of the above statement?

71.
Which of the following are the Keywords used in Scala? Check all that apply.

72.
The expression List.apply(1,2,3) is the same as?

73.
Choose the correct output of the following code fragment?
List("Who","is","longest?").foldLeft((0,""))((i,s) => if (i._1 < s.length) (s.length,s) else i )

74.
The primary tool Scala gives you to organize your programs is the class. A class is a blueprint for objects. Once you do a class, you can create objects from the class blueprint with the keyword new. Which of the following options is described by the above statements?

76.
Which of the following are scala identifiers? Check all that apply.

77.
Choose the best reason why the code fails to compile, for the type hierarchy and expressions as following?
class A { } class B extends A {} class C { } class D extends C { } case class S[T <: A ](a: T*) {} val aa: S[A ] = S[( new B(), new A() ) val cc = S( new D() )

78.
Choose the statement that is not correct about Scala's List?

79.
Which one of the following is a correct example of using toArray to convert to an array and toList to convert to a list?

80.
What will be the output for the code fragment?
List(1, 2, 1, 2, 1, 2, 1, 2, 1, 2).drop(1).sliding(1, 2).flatten.toList

81.
What will be the output for the code fragment below?
List(Set(1), Set(1,2,3), Set(1, 2)) diff List(Set(1,2,3))

82.
Which of the following code snippets correctly represent Type inference on map method of Scala collections?

83.
For the code below, Choose the correct statement?
List.tabulate(100)(a => a.toString)

84.
Create an array buffer just like an array, except that you do not need to specify a size. Which of the following implementation will adjust the allocated space automatically?

85.
Which one of the following code example of Scala collection type for filter is correct?

86.
Which one of the following statement is not correct for trait Iterator?

87.
Traits are used to define _ types by specifying the signature of the supported __?

88.
For the code below, which of the following statement is True?
val data = "test" list = List("this", "is", "a", "test") what will be the effect of applying the expression below to the list list.filterNot(elm => elm == data)

89.
Which of the following is false about Monads?

90.
What is output of the following code?
def main(args: Array[String]) { val capitals = Map("France" -> "Paris", "Japan" -> "Tokyo") println("capitals.get( \"France\" ) : " + capitals.get( "France" )) println("capitals.get( \"India\" ) : " + capitals.get( "India" )) }

91.
Which of the following statement is false for traits?

92.
Which one is not reserved word in Scala?

93.
Which of the following is Web Frameworks of Scala?

94.
Choose the option that best describes the difference between a var and val definition in Scala?

95.
In Scala everything is an Object, No ___?

96.
Choose the best description for the variance expression as following?
A[B <: C]

97.
Which of the following is false about Futures and Promises?

99.
Given the type hierarchy defined below, Choose the most correct statement below?
trait A{ def a = 1 } trait X extends A{ override def a = { println("X") super.a } } trait Y extends A{ override def a = { println("Y") super.a } } For the expression val xy = new AnyRef with X with Y

102.
Choose the best description that describes the Scala classes 'scala.AnyRef ' and 'scala.AnyVal'?

103.
What will the result using the following code?
List(None, Some(1), None, Some(2)).flatMap(x => x)

104.
How can you make a List[String] from a given val x = List[List[String]]?

105.
Which of the following is not valid using List?

106.
What is the output of the following code?
def main(args: Array[String]) { printMe(c = 4, b = 5, a = 7); def printMe( a:Int, b:Int, c:Int) = { println( a,b,c ); } }

107.
The map method on List (and Seq), transforms each element of a collection based on a function. For example, if we have a List[String] and want to convert it to all lowercase?

108.
Choose the statement that is not correct for Scala's mutable.Map?

109.
Choose the correct output using the code fragment below?
listOfInts.sliding(2).toList

110.
How to groupBy using multiple columns in Scala collections?

111.
What is the output of following code?
def main(args: Array[String]) { val x = {print("x");1} lazy val y = {print("y");2} def z = {print("z"); 3} z+y+x+z+y+x }

112.
For the code below, Choose the correct statement that describes an issue with the code?
val L = List[String]() for (a <- 1 to 100) { L :+ a.toString }

113.
What is the output of given code below?
def addInt( a:Int = 5, b:Int = 7 ) : Int = a + b print(addInt(3,7),addInt(3),addInt(),addInt(b=5))

114.
What is the output of the following code?
object MatchTest { def matchTest(x: Any): Any = x match { case 1 => "one" case "two" => 2 case y: Int => "scala.Int" } def main(args: Array[String]) { println(matchTest(2)) } }

115.
Choose the statement that is not correct using the code below?
(1 to 10).par map println

116.
For the code below, Choose the correct statement which shows the output?
var l1 = scala.collection.mutable.MutableList[String]() val l2 = List[String]() for (a <- 1 to 100) { l1 += a.toString } println(l1 .size); for (a <- 1 to 100) { l2 :+ a.toString } println(l2 .size);

117.
Choose the following statement that is not correct for parallel collections?

118.
If Seq is a trait then why is var x = Seq(1, 2, 3) legal?

120.
Scala provides __ versions of all of its collection types. These versions cannot be changed after they are initialized. You should use them whenever you know a collection should not be changed, so that you do not accidentally change it later?

121.
For the code below, choose the correct statement which describes the code?
object A extends B with C { def f(x: Any): Any = ??? }

122.
What is the best way to “clone” a case class?

123.
String interpolation allows users to _____ variable references directly in processed string literals?

125.
Choose the statement that is not correct for trait Traversable?

126.
Read the following code and tell when do Scala functions execute?

127.
For the code fragment below, Choose the expression that shows the correct output?
object Main extends App { val adder = new Adder(2) System.out.println(adder.apply(4)) } class Adder(x: Int) { var y = 5 def apply(y: Int) = x + y }

128.
Choose the statement that best describe's the Scala 'apply' function?

129.
Which of the following is false for Scala?

130.
For the code fragment below choose the correct statement?
val aa = bb filter (x => x % 2 == 0)

133.
Which of the following is true for Objects, Traits and Classes?

134.
Which of the following code statement is correct, Using scala object inside java?