15 Classes & OOP questions from the Kotlin bank, written for Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd.
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A.a language construct that defines a singleton, creating one instance lazily on first access
B.a class declared so the compiler generates equals, hashCode, toString, and copy from its primary constructor properties
C.an object tied to a class that holds members callable through the class name itself, replacing static members
D.a keyword that permits a class or member to be inherited or overridden, which is forbidden by default
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2. Which term means: "a class declared so the compiler generates equals, hashCode, toString, and copy from its primary constructor properties"?
Junior
A.Sealed class
B.Data class
C.Object declaration
D.open modifier
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3. Which statement is correct?
Junior
A.Data class — a restricted hierarchy whose direct subclasses are all known at compile time, enabling exhaustive branching
B.Data class — a class declared so the compiler generates equals, hashCode, toString, and copy from its primary constructor properties
C.Data class — a keyword that permits a class or member to be inherited or overridden, which is forbidden by default
D.Data class — a language construct that defines a singleton, creating one instance lazily on first access
Answer + AI explanation with Pro
4. What is Sealed class?
Mid
A.a keyword that permits a class or member to be inherited or overridden, which is forbidden by default
B.a restricted hierarchy whose direct subclasses are all known at compile time, enabling exhaustive branching
C.an object tied to a class that holds members callable through the class name itself, replacing static members
D.a class declared so the compiler generates equals, hashCode, toString, and copy from its primary constructor properties
Answer + AI explanation with Pro
5. Which term means: "a restricted hierarchy whose direct subclasses are all known at compile time, enabling exhaustive branching"?
Mid
A.Data class
B.open modifier
C.Companion object
D.Sealed class
Answer + AI explanation with Pro
6. Which statement is correct?
Mid
A.Sealed class — a language construct that defines a singleton, creating one instance lazily on first access
B.Sealed class — a restricted hierarchy whose direct subclasses are all known at compile time, enabling exhaustive branching
C.Sealed class — a class declared so the compiler generates equals, hashCode, toString, and copy from its primary constructor properties
D.Sealed class — a keyword that permits a class or member to be inherited or overridden, which is forbidden by default
Answer + AI explanation with Pro
7. What is Object declaration?
Mid
A.a class declared so the compiler generates equals, hashCode, toString, and copy from its primary constructor properties
B.an object tied to a class that holds members callable through the class name itself, replacing static members
C.a language construct that defines a singleton, creating one instance lazily on first access
D.a restricted hierarchy whose direct subclasses are all known at compile time, enabling exhaustive branching
Answer + AI explanation with Pro
8. Which term means: "a language construct that defines a singleton, creating one instance lazily on first access"?
Mid
A.Sealed class
B.Companion object
C.Object declaration
D.Data class
Answer + AI explanation with Pro
9. Which statement is correct?
Mid
A.Object declaration — a restricted hierarchy whose direct subclasses are all known at compile time, enabling exhaustive branching
B.Object declaration — an object tied to a class that holds members callable through the class name itself, replacing static members
C.Object declaration — a language construct that defines a singleton, creating one instance lazily on first access
D.Object declaration — a class declared so the compiler generates equals, hashCode, toString, and copy from its primary constructor properties
Answer + AI explanation with Pro
10. What is Companion object?
Mid
A.a restricted hierarchy whose direct subclasses are all known at compile time, enabling exhaustive branching
B.a keyword that permits a class or member to be inherited or overridden, which is forbidden by default
C.an object tied to a class that holds members callable through the class name itself, replacing static members
D.a language construct that defines a singleton, creating one instance lazily on first access
Answer + AI explanation with Pro
11. Which term means: "an object tied to a class that holds members callable through the class name itself, replacing static members"?
Mid
A.Companion object
B.Data class
C.Sealed class
D.Object declaration
Answer + AI explanation with Pro
12. Which statement is correct?
Mid
A.Companion object — an object tied to a class that holds members callable through the class name itself, replacing static members
B.Companion object — a keyword that permits a class or member to be inherited or overridden, which is forbidden by default
C.Companion object — a language construct that defines a singleton, creating one instance lazily on first access
D.Companion object — a class declared so the compiler generates equals, hashCode, toString, and copy from its primary constructor properties
Answer + AI explanation with Pro
13. What is open modifier?
Junior
A.a class declared so the compiler generates equals, hashCode, toString, and copy from its primary constructor properties
B.a keyword that permits a class or member to be inherited or overridden, which is forbidden by default
C.a restricted hierarchy whose direct subclasses are all known at compile time, enabling exhaustive branching
D.an object tied to a class that holds members callable through the class name itself, replacing static members
Answer + AI explanation with Pro
14. Which term means: "a keyword that permits a class or member to be inherited or overridden, which is forbidden by default"?
Junior
A.open modifier
B.Data class
C.Companion object
D.Object declaration
Answer + AI explanation with Pro
15. Which statement is correct?
Junior
A.open modifier — a restricted hierarchy whose direct subclasses are all known at compile time, enabling exhaustive branching
B.open modifier — an object tied to a class that holds members callable through the class name itself, replacing static members
C.open modifier — a language construct that defines a singleton, creating one instance lazily on first access
D.open modifier — a keyword that permits a class or member to be inherited or overridden, which is forbidden by default
Answer + AI explanation with Pro
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