Advanced Classes Nullability and Collections INTRODUCTION

PRACTICE QUIZ: KNOWLEDGE CHECK: DATA CLASSES

1. When the following code runs, what will the output be?

class Value(val value: Int)
 
fun main() {
val value1 = Value(42)
val value2 = Value(42)
println(value1 == value2)
}

2. When the following code runs, what will the output be?

data class Value(val value: Int)
 
fun main() {
val value1 = Value(42)
val value2 = Value(42)
println(value1 == value2)
}

3. When the following code runs, what will the output be?

class Value(val value: Int)
 
fun main() {
val value = Value(42)
println(value)
}

4. When the following code runs, what will the output be?

data class Value(val value: Int)
 
fun main() {
val value = Value(42)
println(value)
}

5. When the following code runs, what will the output be?

data class Value(val value: Int)
 
fun main() {
val (value) = Value(42)
println(value)
}

6. When the following code runs, what will the output be?

data class FullName( 
    val name: String, 
    val surname: String 
)
 
fun main() { 
    val name = FullName("Marie", "Sklodowska") 
    val newName = name.copy(surname = "Sklodowska-Curie") 
    println(newName) 
} 

7. What is created when you use the to function between two values?

to "AAA"

8. You are programming a coffee machine with a set number of choices and want to specify attributes to each choice. Which one of the following classes will you use?     

9. You are programming dog names and ages using a data modifier. Which of the following is true about data modifiers? Select all that apply.     

PRACTICE QUIZ: KNOWLEDGE CHECK: ENUM CLASSES

1. What are the advantages of using enum classes to represent a set of values? Select all that apply.

2.What is the result of the following code?

enum class Letter { 
A, 
B, 
C, 
} 
 
fun main() { 
println(Letter.C) 
} 

3. What is the result of the following code?

enum class Letter { 
    A, 
    B, 
    C, 
} 
 
 

fun main() { 

    println(Letter.B.ordinal) 
} 

4. What must be added to the following code so that ABC is printed?

enum class Letter { 
    A, 
    B, 
    C, 
} 
 
 

fun main() { 

    for (l in ______) { 

    print(l) 

    } 
} 

5. What is the result of the following code?

enum class Letter(val smallLetter: Char) { 
    A('a'), 
    B('b'), 
    C('c'), 
} 
 
fun main() { 
    println(Letter.A.smallLetter) 
} 

6. You are programming three different payment methods for an online shop and use enum classes. Which of the following is a useful feature of enum classes? Select all that apply.   

PRACTICE QUIZ: KNOWLEDGE CHECK: SPECIAL KINDS OF CLASSES

1. What is the expected result of the following code?

class E: Throwable("E")
fun a() { 
    print("B") 
    throw E() 
    print("C") 
} 
fun main() { 
  try { 
      print("A") 
      a() 
      print("D") 
      } catch (e: E) { 
        print(e.message) 
      } 
      print("F") 
} 

2. What is the expected result of the following code?

fun a() { 
    throw Throwable("Some message") 
} 
 

fun main() { 
    try { 
      print("A") 
      a() 
      } finally { 
        print("F") 
      } 
} 

3. Is the following code going to compile?

enum class PaymentMethod { 
    CHECK 
} 
fun makePayment(method: PaymentMethod) { 
    //... 
} 
fun main() { 
     makePayment("CHECK") 
} 

4. What modifier is used to represent restricted hierarchies? 

5. What is a good example of an enum class? Select all that apply.

6. You have defined an annotation. What happens when you place this annotation in front of a method?

 7. Exceptions happen when you try to code and make an illegal operation. To catch the exception you will use ‘try-catch block.’  

PRACTICE QUIZ: SELF-REVIEW: PRACTICE HANDLING NULLABILITY

1. In step 2 of the exercise, if you pass a null value to  getStudentById(130), what will the output of the function be? 

2. Inside the  searchInStudents function, you return a nullable value of Student. If you want to return a non-nullable value, will the following code will achieve that?

fun searchInStudent(name:String):Student{ 
return stundents.find{it.fullName.lowercase()==name}!! 
}  

3. Given this piece of code:

val s :String?=null  
val l = if (s!=null) s.length else throw NullPointerException() 

4. You have an application and you want users to fill in their names. Which of the following have nullable types? Select all that apply.    

5. How can you deal with nulls in Kotlin? Select all that apply.    

PRACTICE QUIZ: KNOWLEDGE CHECK: COLLECTIONS

1. Complete the following sentence: “Lists…”. Select all that apply.

2. Complete the following sentence: “Sets…”. Select all that apply.

3. Complete the following sentence: “Maps…”. Select all that apply.

4. What is the result of the following code?

fun main() {
    val l = listOf("A", "B", "C")
    println(l[1])
}

5. What is the result of the following code?

fun main() {
val l = listOf("A", "B")
val l2 = listOf("D")
print(l + "C" + l2)
print(l)
} 

6. What is the result of the following code?

fun main() {
    val s = setOf("A", "B", "A")
    print(s)
}

7. What is the result of the following code?

fun main() {
    val m = mapOf('a' to "Alex", 'a' to "Anna")
    print(m)
}

8. What is the result of the following code?

fun main() {
    val m = mapOf('a' to "Alex", 'b' to "Barbara")
    print(m['b'])
}

9. What is the result of the following code?

fun main() {
    val m = mapOf('a' to "Alex", 'b' to "Barbara")
    print(m['c'])
}

10. What is the result of the following code?

fun main() {
    print(listOf("A", "B", "C").size)
    print(setOf(0).size)
    print(mapOf('a' to "Alex", 'b' to "Barbara").size)
}

11. You have a list of food choices. What will you use to iterate over the list?     

12. You want to create an online shop with multiple products and delivery methods. Which one of the following collection types would you use?      

PRACTICE QUIZ: SELF REVIEW: PRACTICE USING COLLECTIONS

1. You created a Comment class in steps 1 and 2 of the exercise. In these steps, which one of the following Kotlin collections did you use to store the comments of the authors?

2. In step 4, you created the relationship between the user and the author of comments. Which one of the following Kotlin collections did you use to create this relationship?

3. In step 5, you filtered and displayed comments. As part of this task, you iterated over the comments list using a for loop.

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QUIZ: MODULE QUIZ: ADVANCED CLASSES AND OBJECTS

1. _________________ is used for classes that are used to represent a bundle of data.

2. What function of a data class creates a copy of an object

3. What is the output of the code below?

class Dog(val name: String)
 
fun main() {
    val pluto1 = Dog("Pluto")
    val pluto2 = Dog("Pluto")
 
    println(pluto1 == pluto2)
}

4. What will the output be of the printAddress function in the code below?

class Address(val city: String?, val state: String?) {
 
}
 
fun printAddress(address: Address) {
    val city: String = address.city ?: "(unknown city)"
    val state: String = address.state ?: "(unknown state)"
    println("$city $state")
}
 
fun main() {
    printAddress(Address("Lagos", "Lagos"))
}

5. What is the output of the consumeStr function?

fun consumeStr(str: String?) {
    print(str?.length)
    print(str?.uppercase())
}
 
fun main() {
    consumeStr("abc")
}

6. __________ method is used to check if a set is empty.

7. What will be the output of the println be?

fun main() {
    val list = listOf("A", "B", "C")
    println(list[2])
}

8. What will the output of the println be?

fun main() {
    val letters = listOf("A", "B", "C")
    println(list.contains("A"))
}

9. The ____________ class has it constructors protected by default.

10. Enums are defined by using the _____________keyword in front of a class.

11. An instance of enum class can be created using constructors.

12. When you run the code below what will the output be of the println statement be?

fun main() {
    val (a, b, c) = Triple(2, "x", listOf(null))
    println(a)
}

13. Which operator converts a nullable type to its non-nullable form forcibly?

14. This is an animal interface class; what is missing in the code below?

Animal {
    fun bark()
    fun run() { // optional body
    f}
}

15. A ______________ object does not allow you to directly call any methods or properties on it.

16. To initialize an immutable list, the _________ function is used.

17. Interfaces are different from abstract classes as interfaces cannot store state.

18. __________ is an exception expression, which means it can have a return value.

19. You 11 ___________ property. 

20. The code below is a valid implementation of an interface.

interface I {
    val a: Int = 123
}

21. Any class that extends “Throwable” can be used as an exception.

22. The function used to add items to a list is called ____.

23. True or False: The code snippet below is a valid way of creating an enum in Kotlin.

class Gender{
  MALE,
  FEMALE
}

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