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Kotlin MCQs and Answers With Explanation: Kotlin is a popular programming language that has gained significant traction among developers worldwide, especially those working on Android applications. To help developers prepare for Kotlin interviews and assessments, we have curated a set of top 30 Kotlin MCQs and answers with explanations.
Kotlin Multiple Choice Questions and Answers
This Kotlin quiz is designed to test your knowledge and understanding of various Kotlin concepts, including syntax, data types, classes, functions, and more. In this article, we present Kotlin multiple choice questions and answers that will help you assess and enhance your Kotlin skills.
Kotlin MCQs and Answers
| Name | Kotlin |
| Exam Type | MCQ (Multiple Choice Questions) |
| Category | Technical Quiz |
| Mode of Quiz | Online |
Top 30 Kotlin MCQs
1. What is Kotlin?
a) A programming language
b) A database
c) An operating system
d) A markup language
Ans: a) A programming language
Explanation: Kotlin is a statically-typed programming language developed by JetBrains. It runs on the Java Virtual Machine (JVM) and can also be compiled to JavaScript or native code. Kotlin is designed to be concise, expressive, and safe, and it is particularly well-suited for developing Android applications.
2. Which of the following is true about Kotlin?
a) It is a functional programming language
b) It is an object-oriented programming language
c) It is a procedural programming language
d) It is a scripting language
Ans: b) It is an object-oriented programming language
Explanation: Kotlin is an object-oriented programming language, which means that it is designed to model real-world entities as objects with properties and methods. However, Kotlin also supports functional programming constructs, such as higher-order functions and lambdas.
3. What is the main advantage of using Kotlin over Java?
a) Better performance
b) Better memory management
c) More concise syntax
d) Better support for multi-threading
Ans: c) More concise syntax
Explanation: One of the main advantages of using Kotlin over Java is that Kotlin has a more concise and expressive syntax. This makes Kotlin code easier to read and write, and can also help reduce the amount of code that needs to be written. Additionally, Kotlin has many other features that make it easier to write safe, expressive, and concise code.
4. Which of the following is a feature of Kotlin?
a) Checked exceptions
b) Null pointer exceptions
c) Extension functions
d) Multiple inheritance
Ans: c) Extension functions
Explanation: Kotlin supports extension functions, which allow developers to add new functions to existing classes without modifying the original class. This can be useful when working with third-party libraries or when adding new functionality to existing code.
5. Which of the following is true about Kotlin’s null safety?
a) Kotlin does not allow null values
b) Kotlin uses the ! operator to denote nullability
c) Kotlin uses the ? operator to denote nullability
d) Kotlin uses the ?? operator to denote nullability
Ans: c) Kotlin uses the ? operator to denote nullability
Explanation: Kotlin uses the ? operator to denote nullability, which means that a variable of that type can be either a non-null value or null. This is a safer approach than Java’s handling of null values, which can lead to null pointer exceptions.
6. Which of the following is true about Kotlin’s type system?
a) Kotlin’s type system is similar to Java’s
b) Kotlin’s type system is more strict than Java’s
c) Kotlin’s type system is less strict than Java’s
d) Kotlin’s type system does not allow inheritance
Ans: b) Kotlin’s type system is more strict than Java’s
Explanation: Kotlin’s type system is more strict than Java’s, which means that it can help catch errors at compile time rather than at runtime. For example, Kotlin’s use of null safety helps prevent null pointer exceptions, and its use of generics helps ensure type safety.
7. What is a data class in Kotlin?
a) A class that is used to represent data structures
b) A class that is used to perform database operations
c) A class that is used to store constants
d) A class that is used to handle exceptions
Ans: a) A class that is used to represent data structures
Explanation: A data class in Kotlin is a special type of class that is used to represent data structures. It is designed to be concise and to eliminate boilerplate code. Data classes automatically generate toString(), equals(), hashCode(), and copy() methods based on the class properties, which can be very useful when working with data.
8. What is a lambda in Kotlin?
a) A function that is passed as an argument to another function
b) A class that is used to represent data structures
c) A type of variable in Kotlin
d) A keyword used to define classes
Ans: a) A function that is passed as an argument to another function
Explanation: A lambda in Kotlin is a function that can be passed as an argument to another function. It is similar to an anonymous inner class in Java, but with a more concise syntax. Lambdas can be used to implement functional programming constructs such as higher-order functions, map, filter, and reduce.
9. What is the Elvis operator in Kotlin?
a) A binary operator used to perform mathematical operations
b) An operator used to compare two values
c) An operator used to check for null values
d) An operator used to perform type conversion
Ans: c) An operator used to check for null values
Explanation: The Elvis operator in Kotlin is a shorthand way of handling null values. It is represented by the symbol ?: and can be used to provide a default value in case a nullable variable is null. For example, val name: String? = null val length = name?.length ?: 0 will set length to 0 if name is null.
10. Which of the following is true about Kotlin’s when expression?
a) It is similar to the switch statement in Java
b) It is used to declare variables
c) It can only be used with Boolean values
d) It is used to handle exceptions
Ans: a) It is similar to the switch statement in Java
Explanation: Kotlin’s when expression is similar to the switch statement in Java, but with a more flexible syntax. It can be used to compare a value against multiple possible values and execute different code blocks depending on the result. When expressions can be used with any type of value, not just integers, and can also be used with more complex conditions.
11. What is the purpose of the apply() function in Kotlin?
a) To create a new instance of a class
b) To modify the properties of an existing instance of a class
c) To perform mathematical calculations
d) To handle exceptions
Ans: b) To modify the properties of an existing instance of a class
Explanation: The apply() function in Kotlin is used to modify the properties of an existing instance of a class. It allows you to write more concise and readable code when initializing objects. The apply() function takes a lambda as its argument, and inside the lambda, you can modify the properties of the object using the this keyword.
12. What is the purpose of the let() function in Kotlin?
a) To create a new instance of a class
b) To modify the properties of an existing instance of a class
c) To perform mathematical calculations
d) To perform a null-check and execute code only if the value is not null
Ans: d) To perform a null-check and execute code only if the value is not null
Explanation: The let() function in Kotlin is used to perform a null-check and execute code only if the value is not null. It takes a lambda as its argument, and inside the lambda, you can write code that should only be executed if the value is not null. The let() function is often used in combination with the safe call operator (?.).
13. What is a companion object in Kotlin?
a) An object that is used to store constants
b) An object that is used to represent data structures
c) An object that is used to create instances of a class
d) An object that is used to define static members of a class
Ans: d) An object that is used to define static members of a class
Explanation: In Kotlin, a companion object is an object that is tied to a specific class and allows you to define static members of that class. This includes properties, methods, and even interfaces. The companion object is declared using the companion keyword inside the class, and its members can be accessed using the class name as a qualifier, just like static members in Java.
14. Which of the following is true about Kotlin’s data classes?
a) They must implement the Serializable interface
b) They are final by default and cannot be extended
c) They cannot have any properties
d) They must implement the equals() and hashCode() methods
Ans: d) They must implement the equals() and hashCode() methods
Explanation: In Kotlin, data classes are used to represent data and are automatically generated with a toString(), equals(), hashCode(), and copy() method based on their properties. These methods are generated by default, and you can override them if needed. Data classes do not need to implement the Serializable interface and can have properties just like regular classes.
15. What is a sealed class in Kotlin?
a) A class that is used to represent data structures
b) A class that is used to create instances of a class
c) A class that is used to store constants
d) A class that is used to define a closed set of subclasses
Ans: d) A class that is used to define a closed set of subclasses
Explanation: In Kotlin, a sealed class is used to define a closed set of subclasses that are known at compile-time. This allows you to create an exhaustive set of subclasses that can be used in pattern matching and other constructs. Sealed classes are declared using the sealed keyword and can only be extended within the same file.
16. What is the purpose of the inline keyword in Kotlin?
a) To allow a function to be called recursively
b) To allow a function to be called from another module
c) To allow a function to be inlined at the call site
d) To allow a function to be declared as private
Ans: c) To allow a function to be inlined at the call site
Explanation: In Kotlin, the inline keyword is used to allow a function to be inlined at the call site. This means that the code of the function is inserted directly into the calling code, which can improve performance by reducing the overhead of function calls. However, inlining functions can also increase code size and reduce the effectiveness of the cache, so it should be used judiciously.
17. Which of the following is true about the lazy initialization in Kotlin?
a) It is used to delay the initialization of a variable until it is accessed for the first time
b) It is used to initialize a variable with a default value
c) It is used to declare a variable as immutable
d) It is used to perform a null-check on a variable
Ans: a) It is used to delay the initialization of a variable until it is accessed for the first time
Explanation: In Kotlin, the lazy initialization is used to delay the initialization of a variable until it is accessed for the first time. This can be useful when you have a variable that is expensive to initialize or that might not be needed at all. To use lazy initialization, you can declare the variable using the lazy() function and provide a lambda that initializes the variable.
18. What is the difference between var and val in Kotlin?
a) var is used to declare a variable as nullable, while val is used to declare a variable as non-nullable
b) var is used to declare a mutable variable, while val is used to declare an immutable variable
c) var is used to declare a variable as public, while val is used to declare it as private
d) var is used to declare a variable as final, while val is used to declare it as non-final
Ans: b) var is used to declare a mutable variable, while val is used to declare an immutable variable
Explanation: In Kotlin, var is used to declare a variable that can be reassigned, while val is used to declare a variable that cannot be reassigned after it is initialized. This means that val is used to declare immutable variables. Both var and val can be used to declare nullable or non-nullable variables, and their visibility can be controlled using access modifiers.
19. What is the Elvis operator in Kotlin?
a) An operator used to perform arithmetic operations
b) An operator used to concatenate strings
c) An operator used to perform null-safe calls
d) An operator used to declare lambda expressions
Ans: c) An operator used to perform null-safe calls
Explanation: In Kotlin, the Elvis operator (?:) is used to perform null-safe calls. It is used to return the left-hand side of the expression if it is not null, or the right-hand side if the left-hand side is null. This can be useful for avoiding NullPointerExceptions when working with nullable variables.
20. What is the difference between the safe call operator (?.) and the non-null assertion operator (!!)?
a) The safe call operator returns null if the expression is null, while the non-null assertion operator throws an exception
b) The safe call operator throws an exception if the expression is null, while the non-null assertion operator returns null
c) The safe call operator performs a null-check before accessing the expression, while the non-null assertion operator does not
d) The safe call operator is used for nullable expressions, while the non-null assertion operator is used for non-nullable expressions
Ans: c) The safe call operator performs a null-check before accessing the expression, while the non-null assertion operator does not
Explanation: In Kotlin, the safe call operator (?.) is used to perform a null-check before accessing a property or calling a method on an object. If the expression is null, the operator returns null instead of throwing a NullPointerException. The non-null assertion operator (!! or .) is used to assert that an expression is not null and can be safely accessed. If the expression is null, a NullPointerException is thrown.
21. What is the purpose of the lateinit keyword in Kotlin?
a) To declare a variable as lazy-initialized
b) To declare a variable as immutable
c) To declare a variable as mutable
d) To declare a variable as initialized later
Ans: d) To declare a variable as initialized later
Explanation: In Kotlin, the lateinit keyword is used to declare a variable as initialized later. This is useful when you have a variable that cannot be initialized in the constructor or when you want to delay the initialization of a variable. You must initialize the variable before accessing it, or a NullPointerException will be thrown.
22. What is the difference between an open class and a final class in Kotlin?
a) An open class can be extended, while a final class cannot be extended
b) An open class can be instantiated, while a final class cannot be instantiated
c) An open class can be declared as nullable, while a final class cannot be declared as nullable
d) An open class can be declared as private, while a final class cannot be declared as private
Ans: a) An open class can be extended, while a final class cannot be extended
Explanation: In Kotlin, an open class is a class that can be extended by other classes, while a final class is a class that cannot be extended. This means that you can create a subclass of an open class, but you cannot create a subclass of a final class. This can be useful for controlling the inheritance hierarchy of your code and preventing unintended inheritance.
23. What is the difference between a function and a lambda expression in Kotlin?
a) A function is a named block of code, while a lambda expression is an anonymous block of code
b) A function can take arguments, while a lambda expression cannot take arguments
c) A function returns a value using the return keyword, while a lambda expression returns a value using the last expression in the block
d) A function can be called using its name, while a lambda expression must be passed as a parameter to another function
Ans: a) A function is a named block of code, while a lambda expression is an anonymous block of code
Explanation: In Kotlin, a function is a named block of code that can be called using its name and can take arguments and return values. A lambda expression, on the other hand, is an anonymous block of code that can be passed as a parameter to another function and can capture variables from its surrounding scope. While functions and lambda expressions can have similar syntax and behavior, they serve different purposes in your code.
24. What is the difference between a top-level function and a member function in Kotlin?
a) A top-level function is defined outside of a class, while a member function is defined inside a class
b) A top-level function is defined inside a class, while a member function is defined outside of a class
c) A top-level function is static, while a member function is non-static
d) A top-level function can only be called from inside a class, while a member function can be called from anywhere
Ans: a) A top-level function is defined outside of a class, while a member function is defined inside a class
Explanation: In Kotlin, a top-level function is a function that is defined outside of a class and can be called from anywhere in your code. A member function, on the other hand, is a function that is defined inside a class and can only be called on instances of that class. Member functions can access the properties and methods of the class, while top-level functions cannot.
25. What is the purpose of the when expression in Kotlin?
a) To replace if-else statements with a more concise syntax
b) To perform pattern matching on an expression
c) To loop over a collection of elements
d) To perform arithmetic operations on numeric values
Ans: b) To perform pattern matching on an expression
Explanation: In Kotlin, the when expression is used to perform pattern matching on an expression. It is similar to a switch statement in other languages, but it can be used with any type of expression and can have multiple branches. When a when expression is evaluated, each branch is checked in order until a matching branch is found. If no branch matches, the default branch is executed.
26. What is the purpose of the with function in Kotlin?
a) To perform a null-safe call on an object
b) To apply a block of code to an object
c) To filter a collection of objects based on a condition
d) To map a collection of objects to a different type
Ans: b) To apply a block of code to an object
Explanation: In Kotlin, the with function is used to apply a block of code to an object. The object becomes the receiver of the function, and you can call its methods and properties directly within the block. This can be useful for avoiding repetitive code and improving readability.
27. What is the purpose of the apply function in Kotlin?
a) To perform a null-safe call on an object
b) To apply a block of code to an object and return the object
c) To filter a collection of objects based on a condition
d) To map a collection of objects to a different type
Ans: b) To apply a block of code to an object and return the object
Explanation: In Kotlin, the apply function is used to apply a block of code to an object and return the object. The object becomes the receiver of the function, and you can call its methods and properties directly within the block. The apply function is similar to the with function, but it returns the object instead of a Unit value. This can be useful for chaining operations together or for initializing an object with multiple properties.
28. What is the difference between a nullable and non-nullable variable in Kotlin?
a) A nullable variable can be null or have a value, while a non-nullable variable can only have a value
b) A nullable variable can only have a value, while a non-nullable variable can be null or have a value
c) A nullable variable can be cast to any other type, while a non-nullable variable cannot be cast
d) A nullable variable can only be accessed within a try-catch block, while a non-nullable variable can be accessed anywhere
Ans: a) A nullable variable can be null or have a value, while a non-nullable variable can only have a value
Explanation: In Kotlin, a nullable variable is a variable that can have a null value or a non-null value, while a non-nullable variable can only have a non-null value. Nullable variables are denoted with a question mark (?), while non-nullable variables do not have this notation. When you access a nullable variable, you need to use safe calls or null checks to avoid null pointer exceptions.
29. What is the purpose of the Elvis operator in Kotlin?
a) To assign a default value to a nullable variable if it is null
b) To assign a default value to a non-nullable variable if it is null
c) To concatenate two strings together
d) To perform arithmetic operations on numeric values
Ans: a) To assign a default value to a nullable variable if it is null
Explanation: In Kotlin, the Elvis operator (?:) is used to assign a default value to a nullable variable if it is null. The syntax of the operator is variable ?: defaultValue, where variable is the nullable variable and defaultValue is the value that is assigned if variable is null. This can be useful for providing default values in cases where you do not want to allow null values.
30. What is the purpose of the lateinit keyword in Kotlin?
a) To declare a variable that can be null
b) To declare a variable that must be initialized before it is used
c) To declare a variable that is initialized lazily
d) To declare a variable that can be re-assigned after it is initialized
Ans: b) To declare a variable that must be initialized before it is used
Explanation: In Kotlin, the lateinit keyword is used to declare a variable that must be initialized before it is used. This keyword is useful when you need to declare a variable that cannot be initialized in the constructor or when you want to defer initialization until later in the code. The lateinit keyword is only valid for mutable properties of non-null types that do not have a custom getter or setter. If you try to access a lateinit property before it is initialized, a NullPointerException will be thrown.
Kotlin is a modern programming language that offers numerous advantages over other languages. The Kotlin MCQs and Answers With Explanation presented here provide a valuable resource for learners and professionals seeking to enhance their understanding of this language. Follow us @ freshersnow.com to learn more.