Kotlin Programming MCQ for Competitive Exams, Interviews, and Certifications

71

What is the difference between a and b?

var a: String? = "KotlinProgramming"
var b: String = 'KotlinProgramming"

A) a is volatile as in Java B) a is final and cannot be changed C) b can never become null D) b is final and cannot be changed

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Answer & Solution

Answer: Option C

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72

Which is true for the following simple class declaration?

class Person (val name: String)

A) It is public B) It has a private property "name" C) It can be extended by other classes D) It is package-private

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Answer & Solution

Answer: Option A

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73

The code below compiled and executed without issue before the addition of the line declaring errorStatus. Why does this line break the code?

sealed class Status(){
  object Error : Status()
  class Success : Status()
}
fun main(){
  var successStatus = Status.Success()
  var errorStatus = Status.Error()
}

A) StatusError is an object, not a class and cannot be instantiated B) Only one instance of the class Status can be instantiated at a time C) Status.Error must be declared as an immutable type D) Status.Error is pribate to class and cannot be declared externally

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Answer & Solution

Answer: Option A

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74

The code below is expected to display the numbers from 1 to 10, but it does not. Why?

val seq = sequence { yieldAll(1..20) }
  .filter { it < 11 }
  println(seq)

A) You cannot assign a sequence to a variable B) To produce result, a sequence must have terminal operation. In this case, it needs a .toList() C) The .filter{ it < 11 } should be .filter{ it > 11 } D) The yieldAll(1..20) should be yieldAll(1..10)

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Answer & Solution

Answer: Option B

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75

You have an unordered list of high scores. Which is the simple method to sort the highScores in descending order?

fun main() { val highScores = listOf(4000, 2000, 10200, 12000, 9030)}

A) .sortedByDescending() B) .descending() C) Public D) .sort()

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Answer & Solution

Answer: Option C

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76

What three methods does this class have?

class Person

A) equals(), hashCode(), and toString() B) equals(), toHash(), and super() C) print(), println(), and toString() D) clone(), equals(), and super()

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Answer & Solution

Answer: Option A

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77

In this code snippet, why does the compiler not allow the value of y to change?

for(y in 1..100) y+=2

A) y must be declared with var to be mutable B) y is an implicitly immutable value C) y can change only in a while loop D) In order to change y, it must be declared outside of the loop

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Answer & Solution

Answer: Option B

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78

Both const and @JvmField create constants. What can const do that @JvmField cannot?

class Detail {
  companion object {
    const val COLOR = "Blue"
    @JvmField val SIZE = "Really Big"
  }
}

A) const is compatible with Java, but @JvmField is not B) The compiler will inline const so it is faster and more memory efficient C) Virtually any type can be used with const but not @JvmField D) const can also be used with mutable types

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Answer & Solution

Answer: Option B

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79

You have two arrays, a and b. Which line combines a and b as a list containing the contents of both?

val a = arrayOf(1, 2, 3) val b = arrayOf(100, 200, 3000)

A) Val c = list of (a, b) B) Val c = a + b C) Delegates.observer() D) Val c = listOf(*a, *b)

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Answer & Solution

Answer: Option D

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80

When the Airplane class is instantiated, it displays Aircraft = null, not Aircraft = C130 why?

abstract class Aircraft {
  init { println("Aircraft = ${getName()}") }
  abstract fun getName(): String
}
class Airplane(private val name: String) : Aircraft() {
  override fun getName(): String = name
}

A) Classes are initialized in the same order they are in the file, therefore, Aircraft should appear after Airplane B) The code needs to pass the parameter to the base class's primary constructor. Since it does not, it receives a null C) Abstract function always returns null D) A superclass is initialized before its subclass. Therefore, name has not been set before it is rendered

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Answer & Solution

Answer: Option C

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