Kotlin Tricky Output Questions
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We’ll delve into a set of Kotlin Tricky Output Questions designed to test and deepen your understanding of key language features. Whether you’re preparing for a job interview or simply aiming to enhance your Kotlin proficiency, these questions will guide you through scenarios that explore nuances in the language, unraveling the mysteries of output variations.
1. Nullable Types
What will be the output?
Answer:
📖This code will throw a NullPointerException at runtime because of the use of the non-null assertion (!!) on a nullable variable (name).
2. Smart Casts
What will be the output?
Answer:
📖The output will be 14, including the comma and the space, as the value is smart cast to String inside the if block, and its length property is accessed.
3. Data Classes
What will be the output?
Answer:
📖 The output will be false because person1 and person2 are distinct objects, and the == checks for structural equality.
4.Lambda Expressions and Scoping
What will be the output?
Answer:
📖The lambda captures and modifies the counter variable each time it's invoked.
5.Property Delegation
What will be the output?
Answer:
📖 The observable delegate prints changes to the name property.
6.Generics and Variance
What will be the output?
Answer:
📖 Box is a generic class that takes a type parameter T. The out modifier in the generic type parameter declaration (out T) indicates that T is a covariant type parameter.
Covariant types allow for widening the type hierarchy: In the context of the Box class, if T is a covariant type, it means that if A is a subtype of B, then Box<A> is considered a subtype of Box<B>.
7. Extension Functions and Companion Objects
What will be the output?
Answer:
📖 The extension function myExtension is called on the companion object of MyClass.
8.Generics and Reified Types
What will be the output?
Answer:
📖 The printType function uses reified types to print the simple names of the types String and Int.
9. Inline Functions
What will be the output?
Answer:
📖 In Kotlin, the return@label statement inside a lambda refers to the nearest enclosing function with the specified label. In this case, return@performOperation is intended to return from the performOperation function. However, the inline nature of the function affects the behavior.
In an inline function, the lambda passed to it can be inlined at the call site. In this scenario, the return@performOperation statement does not return from the performOperation function, but it returns from the lambda itself, effectively skipping the remaining code inside the lambda.
10.Mutable Lists and References
What will be the output?
Answer:
📖 Both numbers and otherNumbers refer to the same underlying list object. Modifying one list will affect the other as well.
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