Scala MCQ Questions Answers

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 option is described by the above statements?

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

49. Which one 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. Correct statements that describe a Scala Case class?

53. Which one describes 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 one is described by the above statement?

55. Which one is not valid in Scala?

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

57. Which one is equivalent to the code below?

58. Which are types of function in Scala?

59. Which statement is about Scala anonymous function?

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

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

62. Which are the 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 code is true?

65. Which 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 statement is false about Scala?

69. Choose statement that best describes the line def?

70. Which are correct in context of the above statement?

71. Which are the Keywords used in Scala?

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

73. Correct output of given code fragment?

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 option is described by the above statements?

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 option is described by the above statements?

76. Which are scala identifiers?

77. Reason why the code fails to compile, for the type hierarchy and expressions as following?

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

79. Correct example of using toArray to convert to an array and toList to convert to a list?

80. Output for the code fragment?

81. Output for the code below?

82. Which code snippet correctly represent Type inference on map method of Scala collections?

83. For the code below, Choose the correct statement?

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

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

86. Which 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 statement is True?

89. Which one is false about Monads?

90. What's the output?

91. Which statement is false for traits?

92. Which one is not reserved word in Scala?

93. Which one is Web Frameworks of Scala?

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

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

96. Best description for the variance expression as following?

97. Which one is false about Futures and Promises?

98. For the type heirachy defined below, Choose the most correct statement below for the output?

99. Given the type hierarchy defined below, Choose correct statement below?

100. Choose the expression that allows the code to compile